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Side effect of b12 pills: Vitamin B-12 – Mayo Clinic


Vitamin B-12 – Mayo Clinic


Vitamin B-12 (cobalamin) plays an essential role in red blood cell formation, cell metabolism, nerve function and the production of DNA, the molecules inside cells that carry genetic information.

Food sources of vitamin B-12 include poultry, meat, fish and dairy products. Vitamin B-12 is also added to some foods, such as fortified breakfast cereals, and is available as an oral supplement. Vitamin B-12 injections or nasal spray might be prescribed to treat vitamin B-12 deficiency.

Vitamin B-12 deficiency is not common in the U.S. However, people who follow a vegetarian or vegan diet might be prone to deficiency because plant foods don’t contain vitamin B-12. Older adults and people with digestive tract conditions that affect absorption of nutrients also are susceptible to vitamin B-12 deficiency.

Left untreated, a vitamin B-12 deficiency can lead to anemia, fatigue, muscle weakness, intestinal problems, nerve damage and mood disturbances.

The recommended daily amount of vitamin B-12 for adults is 2.4 micrograms.


Research on the use of vitamin B-12 for specific activities and conditions shows:

  • Heart and blood vessel disease. Researchers had previously believed that vitamin B-12, when combined with folic acid (vitamin B-9) and vitamin B-6, might prevent diseases of the heart and blood vessels by reducing the levels of an amino acid in the blood (homocysteine). However, studies show that the combination of these vitamins doesn’t seem to reduce the risk or severity of cardiovascular disease and stroke.
  • Dementia. Vitamin B-12 deficiency is associated with dementia and low cognitive function, but it’s not clear whether vitamin B-12 supplements might help prevent or treat dementia.
  • Athletic performance. Unless you have a vitamin B-12 deficiency, there’s no evidence that vitamin B-12 supplements will boost your energy or make you a better athlete.

Our take

Generally safe

Most people get enough vitamin B-12 from a balanced diet. However, older adults, vegetarians, vegans and people who have conditions that affect their ability to absorb vitamin B-12 from foods might benefit from the use of oral supplements.

Vitamin B-12 supplements also are recommended for women who are pregnant or breastfeeding exclusively and follow vegetarian or vegan diets.

Safety and side effects

When taken at appropriate doses, vitamin B-12 supplements are generally considered safe. While the recommended daily amount of vitamin B-12 for adults is 2.4 micrograms, higher doses have been found to be safe. Your body absorbs only as much as it needs, and any excess passes through your urine.

High doses of vitamin B-12, such as those used to treat a deficiency, might cause:

  • Headache
  • Nausea and vomiting
  • Diarrhea
  • Fatigue or weakness
  • Tingling sensation in hands and feet


Possible interactions include:

  • Aminosalicylic acid (Paser). Taking this drug used to treat digestive problems might reduce your body’s ability to absorb vitamin B-12.
  • Colchicine (Colcrys, Mitigare, Gloperba). Taking this anti-inflammatory drug used to prevent and treat gout attacks might decrease your body’s ability to absorb vitamin B-12.
  • Metformin (Glumetza, Fortamet, others). Taking this diabetes drug might reduce your body’s ability to absorb vitamin B-12.
  • Proton pump inhibitors. Taking omeprazole (Prilosec), lansoprazole (Prevacid) or other stomach acid-reducing drugs might decrease your body’s ability to absorb vitamin B-12.
  • Vitamin C (ascorbic acid) supplements. Taking vitamin B-12 with vitamin C might reduce the available amount of vitamin B-12 in your body. To avoid this interaction, take vitamin C two or more hours after taking a vitamin B-12 supplement.

Your doctor might recommend changing drugs or timing doses to offset any potential interactions.

July 17, 2021

Show references

  1. Vitamin B12: Fact sheet for professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional. Accessed Jan. 9, 2021.
  2. Fairfield KM. Vitamin supplementation in disease prevention. https://www.uptodate.com/contents/search. Accessed Jan. 9, 2021.
  3. Means RT Jr, et al. Causes and pathophysiology of vitamin B12 and folate deficiencies. https://www.uptodate.com/contents/search. Accessed Jan. 9, 2021.
  4. Cyanocobalamin. IBM Micromedex. https://www.micromedexsolutions.com. Accessed Jan. 9, 2021.
  5. Methylcobalamin. Facts & Comparisons eAnswers. https://www.wolterskluwercdi.com/facts-comparisons-online/. Accessed Jan. 9, 2021.
  6. Vitamin B12. Natural Medicines. https://naturalmedicines.therapeuticresearch.com. Accessed Jan. 9, 2021.


Cyanocobalamin (Vitamin B-12) Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing

The effects of some drugs can change if you take other drugs or herbal products at the same time. This can increase your risk for serious side effects or may cause your medications not to work correctly. These drug interactions are possible, but do not always occur. Your doctor or pharmacist can often prevent or manage interactions by changing how you use your medications or by close monitoring.

To help your doctor and pharmacist give you the best care, be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before starting treatment with this product. While using this product, do not start, stop, or change the dosage of any other medicines you are using without your doctor’s approval.

Some products that may interact with this drug include: drugs that affect the bone marrow (such as chloramphenicol), vitamins/supplements that contain intrinsic factor.

Certain medications can decrease the absorption of vitamin B12, including: colchicine, metformin, extended-release potassium products, antibiotics (such as gentamicin, neomycin, tobramycin), anti-seizure medications (such as phenobarbital, phenytoin, primidone), medications to treat heartburn (such as h3 blockers including cimetidine/famotidine, proton pump inhibitors such as omeprazole/lansoprazole).

Vitamin B12 is an ingredient found in many combination vitamin and nutritional products. Tell your doctor or pharmacist if you are taking other products that contain cyanocobalamin, vitamin B12, or hydroxocobalamin.

Cyanocobalamin may interfere with certain laboratory tests (including intrinsic factor, blood tests for other types of anemia), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

Certain drugs may interfere with laboratory tests for vitamin B12 levels, possibly causing false results. Tell laboratory personnel and all your doctors if you take any of the following: antibiotics (such as amoxicillin, erythromycin), methotrexate, pyrimethamine.

This document does not contain all possible drug interactions. Keep a list of all the products you use. Share this list with your doctor and pharmacist to lessen your risk for serious medication problems.

cyanocobalamin (oral) | Michigan Medicine

What is the most important information I should know about oral cyanocobalamin?

You should not use this medicine if you are allergic to cobalt, or if you have Leber’s disease.

What is oral cyanocobalamin?

Cyanocobalamin is a man-made form of vitamin B12. Vitamin B12 is important for growth, cell reproduction, blood formation, and protein and tissue synthesis.

Cyanocobalamin is used to treat vitamin B12 deficiency in people with pernicious anemia and other conditions.

Cyanocobalamin may also be used for purposes not listed in this medication guide.

What should I discuss with my healthcare provider before taking oral cyanocobalamin?

You should not use this medicine if you are allergic to cobalt, or if you have Leber’s disease. Cyanocobalamin can lead to optic nerve damage (and possibly blindness) in people with Leber’s disease.

Tell your doctor if you have ever had:

  • heart disease;
  • diabetes;
  • a bleeding or blood clotting disorder;
  • gout;
  • an iron or folic acid deficiency;
  • low levels of potassium in your blood; or
  • an intestinal disorder such as ulcerative colitis.

Tell your doctor if you are pregnant or breast-feeding.

Do not give this medicine to a child without medical advice.

How should I take oral cyanocobalamin?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Carefully follow instructions about whether to take your cyanocobalamin with or without food.

Your dose needs may change if you become pregnant, if you breast-feed, or if you eat a vegetarian diet. Tell your doctor about any changes in your diet or medical condition.

Do not swallow a lozenge or sublingual tablet whole. Allow it to dissolve in your mouth without chewing. The sublingual tablet should be placed under your tongue.

Do not crush, chew, or break an extended-release tablet. Swallow it whole with a full glass of water.

You may need frequent medical tests to help your doctor determine how long to treat you with cyanocobalamin.

To treat pernicious anemia, you will have to use cyanocobalamin on a regular basis for the rest of your life. Not using the medication can lead to irreversible nerve damage in your spinal cord.

Pernicious anemia is also treated with folic acid to help maintain red blood cells. However, folic acid will not treat Vitamin B12 deficiency and will not prevent possible damage to the spinal cord. Take all of your medications as directed.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking oral cyanocobalamin?

Avoid drinking large amounts of alcohol. Heavy drinking can make it harder for your body to absorb cyanocobalamin.

What are the possible side effects of oral cyanocobalamin?

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • shortness of breath (even with mild exertion), swelling, rapid weight gain;
  • cough, chest pain; or
  • low potassium level –leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling.

Common side effects may include diarrhea.

  • diarrhea;
  • numbness or tingling;
  • fever;
  • joint pain;
  • swollen tongue; or
  • itching or rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect oral cyanocobalamin?

Tell your doctor about all your other medicines, especially:

  • an antibiotic;
  • drugs that weaken the immune system such as cancer medicine, or steroids;
  • medicine to reduce stomach acid such as cimetidine, omeprazole, lansoprazole, Nexium, Prilosec, or Zantac;
  • oral diabetes medicine that contains metformin; or
  • seizure medication.

This list is not complete. Other drugs may affect cyanocobalamin, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Where can I get more information?

Your pharmacist can provide more information about oral cyanocobalamin.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. (‘Multum’) is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum’s drug information does not endorse drugs, diagnose patients or recommend therapy. Multum’s drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2021 Cerner Multum, Inc. Version: 7.01. Revision date: 7/16/2018.

B12 Shot Side Effects – Do They Outweigh the Risk?

Medically reviewed by Leann Poston, M.D. on 9/29/20

As vitamin B12 continues to gain popularity and attention, many are beginning to wonder what the B12 shot side effects and benefits are? Can this supplement really be as great as everyone keeps saying it is with no risks or side effects? While this treatment still fascinates us today and poses many questions, the history of the development of B12 shots is just as interesting.

In the 1850s, pernicious anemia was essentially a fatal condition – in today’s medicine, pernicious anemia is easily treated with B12 supplements. However, in the 1850s, patients suffered from abnormal gait, exhaustion, and inevitably they ended up in the hospital before they passed. It wasn’t until the 1920s when Georges Richard Minot and William Parry Murphy determined that certain foods (red meat and liver) effectively treated anemia in dogs. Almost 50 years later, Robert Woodward, an organic chemist, successfully synthesized vitamin B12. From this discovery, modern medicine created treatments based on the discovery of vitamin B12’s role in anemia and the successful synthesis of its complex structure.

Thankfully, conditions caused by vitamin B12 deficiencies are incredibly treatable through vitamin B12 supplements. Understanding the B12 shot side effects and benefits can help you manage your expectations of vitamin B12 as a treatment and whether a B12 shot it the best form of treatment.

Vitamin B12 – What It is and What It Does

Vitamin B12, also known as cyanocobalamin, is an important factor in DNA synthesis, the metabolism of every cell within the body, the maturation of developing red blood cells, and the metabolism of fatty acids and amino acids. Because vitamin B12 is such an integral component in the function of a healthy body, maintaining the proper levels of B12 within the body is absolutely necessary to sustain a properly working nervous system and a healthy red blood cell count.

Vitamin B12 is most commonly sourced through foods that come from animals such as fish, red meat, eggs, dairy, cheese, and other dairy products. Those who are vegan or vegetarian sometimes source their B12 through fortified cereals. While many people can consume and absorb the proper amount of vitamin B12 through their dietary choices, many people cannot sustain the proper levels of B12 within their body, which can lead to dangerous conditions if left untreated.

Vitamin B12 deficiencies are rare in otherwise healthy individuals; however, those at an elevated risk at groups who do not consume a diet with animal-sourced food, as well as those suffering from other health conditions. Groups at an increased risk of developing a vitamin B12 deficiency are:

  • Vegans
  • Vegetarians
  • Adults over 50
  • Those with low gastric intrinsic factor
  • Those with a low amount of stomach acid
  • Those taking certain medications
  • Gastrointestinal disorders like Crohn’s disease and celiac disease
  • Those who have had weight loss surgery, bowel resection, or surgery on another part of the digestive tract
  • Those who take metformin and acid-reducing medications
  • Those with specific genetic mutations, such as MTHFR, MTRR, and CBS
  • Those who regularly consume alcoholic beverages (NIH, n.d.)

If someone fits into one of these at-risk groups, it is best to consult your doctor in considering whether or not you should undergo testing to determine if you have a vitamin B12 deficiency. Presently, no one test determines whether or not someone is deficient in vitamin B12. Doctors must consider both lab results and clinical conditions to reach a diagnosis.

Symptoms of B12 Deficiency

Before considering both the B12 shot side effects and the B12 shot benefits, it is important to understand the symptoms of a vitamin B12 deficiency. Individuals cannot procure vitamin B12 without a prescription, and in order to obtain a prescription, you must be deemed deficient. It can be especially tricky to reach this diagnosis as there is no “gold-standard” test, and symptoms can long go unnoticed or be contributed to other causes.

Consider that vitamin B12 is responsible for so many bodily functions; the displayed symptoms and affected body systems can vary greatly. Another problem is that symptoms and their onset tend to increase gradually, again making it hard to connect the dots between symptoms and cause. Listed below are just a few of the symptoms caused by a vitamin B12 deficiency:

  • Abnormal reflexes
  • Tingling, numbness, or other neuropathies
  • Impaired sense of position
  • Weakness in arms or legs
  • Dizziness, vertigo, or balance issues
  • Difficulty walking or abnormal gait
  • Confusion or memory loss
  • Dementia
  • Restless legs
  • Tremors
  • Vision problems
  • Incontinence
  • Impotence
  • Anger and irritability
  • Depression
  • Personality changes
  • Paranoia
  • Mania and/or psychosis
  • Hallucinations
  • Violent and antisocial behavior
  • General weakness
  • Shortness of breath or difficulty breathing
  • White appearance; pallor
  • Fatigue or general tiredness
  • Anemia
  • Coordination and balance problems while walking
  • Difficulty focusing
  • Memory loss
  • Sleep issues
  • Hair loss
  • Constipation
  • Loss of appetite
  • Swollen tongue.
  • Fast heart rate
  • Shortness of breath
  • Mouth pain
  • Irritability
  • Nausea
  • Vomiting
  • Diarrhea
  • Weight loss

Keeping an eye out and paying close attention to these symptoms can help in accurately diagnosing a vitamin B12 deficiency. If you think you may be deficient in vitamin B12, it is important to contact a health care professional and schedule a consultation.

Also read – How to Buy BPC-157 Online Safely

Treatment for Vitamin B12 Deficiency

Fortunately, there are many options in modern medicine to safely and successfully treat vitamin B12 deficiency. There are three main treatment methods – a change in diet, oral supplements, and vitamin B12 injections. For those who aren’t receiving enough vitamin B12 as a result of food choices may be able to treat their deficiency by incorporating more vitamin B12 rich foods in their diets.

However, for those deficient as a result of age, a genetic mutation, stomach issues, or those taking certain medications, a change in diet may not be enough to treat a vitamin B12 deficiency. These individuals will likely have to supplement their diet with an oral B12 supplement or a B12 injection. Oral supplements are considered inferior to the vitamin B12 injections as they take longer to absorb, and some of the nutritional value is lost during digestion in the stomach.

For those receiving B12 shots as a treatment to a B12 deficiency, there are a few different forms, or vitamers, of synthesized vitamin B12 that can be used to handle the deficiency. These include:

  • Cyanocobalamin – This vitamer is used for food fortification, multi-vitamin products, and dietary supplements. Cyanocobalamin is suitable for these methods of treatment because of its stability during processing and storage.
  • Hydroxocobalamin – This vitamer is typically found within the pharmacology. Due to its water solubility, it is commonly used for intramuscular or intravenous injections. Also used to reverse the effects of cyanide poisoning, this vitamer is the preferred course of treatment for those with intrinsic cobalamin metabolic disease and those with optic neuropathy as a symptom of pernicious anemia.
  • Adenosylcobalamin – This vitamer is an active cofactor form of vitamin B12. It naturally occurs in the liver and is active in the mitochondria.
  • Methylcobalamin – This vitamer is an active form of B12 that works with several enzymes to create amino acids, produce red blood cells, repair DNA, and assist with other essential physiological processes. This form of B12 is typically administered through injections and oral supplements.

Determining the right course of treatment for a vitamin B12 deficiency is between the patient and their healthcare provider. Above all, the most important thing is that the deficiency is properly treated, treatment is working well, and the quality of the patient’s life is improving.

Vitamin B12 Shot Benefits

There are both vitamin B12 shot side effects and vitamin B12 shot benefits. Many of the benefits associated with the vitamin B12 shot include better mood, increased energy, alleviating anemia symptoms, weight loss, and many more. Though keep in mind, that these benefits are realized when a vitamin B12 deficiency is reversed. As with any treatment, it is incredibly important to weigh both the risks and benefits associated with the course of treatment. To give you a better idea, listed below are the benefits associated with vitamin B12 shots:

  • Helping with red blood cell formation which may boost energy and endurance
  • May support heart health by decreasing homocysteine levels
  • May help prevent cognitive decline
  • Anemia prevention (NIH, n.d.)
  • May reduce the risk age-related macular degeneration
  • May improve sperm count (Penn State, 2011)

While these are only some of the benefits associate with vitamin B12 shots, it is easy to see that vitamin B12 is responsible for so many functions within the body. Considering a deficiency can cause harm to many systems within the body, understanding the benefits of the B12 shot and know how it could improve the quality of your life is very important to leading a safe and healthy life.

Also read – What is the Right BPC-157 Dosage?

B12 Shot Side Effects

Just as it is important to understand the benefits of the B12 shot, it is also incredibly important to know the B12 shot side effects. Before anyone makes a decision regarding their health, it is imperative that they know the risks and the benefits. Understanding both the B12 shot side effects, as well as the B12 shot side effects at the injection site, is important because it empowers you to make a decision regarding your treatment that is fully informed.

B12 shot side effects include, but are not limited to:

  • Swelling at the injection site
  • Mild diarrhea
  • Itching
  • Swelling in the body
  • Low potassium
  • Headache
  • Dizziness
  • Vomiting
  • Skin rash
  • Pulmonary edema and congestive heart failure (in early treatment)
  • Vein thrombosis
  • Polycythemia vera
  •  A very rare, but serious allergic reaction causing swelling of the face, tongue, and throat, and difficulty swallowing or breathing (anaphylaxis)
  • Restenosis
  • High blood pressure immediately after injection
  • Cold symptoms
  • Anxiety
  • Burning skin
  • Pink or red skin discoloration
  • Joint and muscle pain
  • Facial swelling
  • Numbness
  • Increase and blood volume and red blood cells

Considering the B12 shot side effects listed above, it is important to understand that some of these side effects are more common, while others are incredibly rare. This is another important discussion topic to bring up with your health care provider when evaluating your diagnosis and considering treatment.

Frequently Asked Questions

Below are some common concerns and questions people have when considering a vitamin deficiency and the B12 shot side effects and benefits associated with this specific treatment. Read below to see if a question you may have is present or use these topics as a way to start a conversation with your health care provider.

Are Vitamin B12 Shots More Effective Than Vitamin B12 Oral Supplements?

Both methods of treatment can deliver the desired results, and the majority of the “success” of treatment is determined on a case-by-case basis and what is most comfortable and effective for the individual patient. Some studies have shown that a high-dose, oral vitamin B12 was as effective as an intramuscular injection; however, other studies have determined that oral B12 supplements aren’t as fully absorbed during the digestive process. It’s best to talk with your doctor to determine which form of treatment is best for you.

Are Vitamin B12 Shots painful?

While this is somewhat dependent on the individual’s tolerance for pain, B12 injections are mostly considered to be relatively painless. Injections given into the muscle typically present some pain, swelling, and itching at the injection site. However, these symptoms are mild and wear off pretty quickly.

In Conclusion…

Any time we are faced with unfamiliar medical treatments, it is understandable to have questions and concerns. It makes sense to wonder if the benefits outweigh the B12 shot side effects. Considering how important vitamin B12 is to the optimal function of your body; it seems as though the answer would be, yes.

When you’re ready to talk to your doctor about your prescription for your vitamin B12 deficiency, you will want to ensure that you are sourcing your vitamin B12 supplement from the best place possible.

A great place to source your vitamin B12 supplement is through Invigor Medical. This trusted, U.S. Pharmacy provides high-quality methylcobalamin to those deficient in vitamin B12 with a prescription for an injectable supplement.

To learn more about Invigor Medical and how it can treat your possible B12 deficiency visit – https://invigormedical.com/

Also read – How Can You Get a Cellular Regeneration or Healing Boost?


While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider.  You should always consult a practicing professional who can diagnose your specific case.  The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice. 


  • National Heart, Lung and Blood Institute. (n.d.). Pernicious Anemia. Retrieved from https://www.nhlbi.nih.gov/health-topics/pernicious-anemia
  • Penn State Hershey. (2011). Vitamin B 12 (Cobalamin). Retrieved from http://pennstatehershey.adam.com/content.aspx?productid=107&pid=33&gid=000332

vitamin B12, Athlete (cyanocobalamin) dosing, indications, interactions, adverse effects, and more




USES: Cyanocobalamin is a man-made form of vitamin B12 used to treat low levels (deficiency) of this vitamin. Vitamin B12 helps your body use fat and carbohydrates for energy and make new protein. It is also important for normal blood, cells, and nerves. Most people get enough vitamin B12 in their diet, but a deficiency may occur in certain health conditions (e.g., poor nutrition, pregnancy, stomach/intestinal problems, infection, cancer). Serious vitamin B12 deficiency may result in anemia, stomach problems, and nerve damage.

HOW TO USE: Read the Patient Information Leaflet provided by your pharmacist before you start using this medication and each time you get a refill. Follow the illustrated directions for the proper use of this medication. If you have any questions, consult your doctor or pharmacist.Gently blow your nose before using this drug. If your product needs to be primed, follow the instructions on how to properly prime the bottle.Use this medication in the nose once weekly or as directed by your doctor. Hot food or drinks may produce mucus that can wash away this medication. Avoid hot food or drinks for 1 hour before or after using this medication.For products that contain more than 1 dose, keep track of the number of doses you use from each pump.Dosage is based on your medical condition and response to treatment. Do not increase, decrease, or stop this medication without your doctor’s approval. Use this medication regularly to get the most benefit from it. To help you remember, use it on the same day each week. It may help to mark your calendar with a reminder.

SIDE EFFECTS: Headache, nausea, or runny nose may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.This medication may cause low potassium levels in the blood (hypokalemia). Tell your doctor right away if any of these unlikely but serious side effects occur: muscle cramps, weakness, irregular heartbeat.People who have a rare blood disorder (polycythemia vera) may rarely have symptoms related to this disorder while taking cyanocobalamin. Seek immediate medical attention if any of these rare but very serious symptoms occur: chest pain (especially with shortness of breath), weakness on one side of the body, sudden vision changes, trouble speaking.A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada – Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before using cyanocobalamin, tell your doctor or pharmacist if you are allergic to it; or to cobalt; or if you have any other allergies. Your doctor may recommend that you receive a smaller test dose before starting your regular dose. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: low potassium blood levels (hypokalemia), gout, a certain blood disorder (polycythemia vera), a certain eye disease (Leber’s disease), other vitamin/mineral deficiencies (especially folic acid and iron).Tell your doctor if you develop a stuffy or runny nose (e.g., due to a common cold or allergies) while using this medication. You may need to use another form of vitamin B12 when these symptoms are present.During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.Based on information from related drugs, this medication may pass into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: drugs that may affect blood cell production (e.g., chloramphenicol, anti-cancer drugs, HIV drugs), other vitamins/nutritional supplements (especially folic acid).Certain other drugs may interfere with laboratory tests for vitamin B12 levels, possibly causing false test results. Tell laboratory personnel and all your doctors if you take any of the following: anti-infective drugs (e.g., amoxicillin, erythromycin), methotrexate, pyrimethamine.This document does not contain all possible interactions. Before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: Overdose with this medication is very unlikely. However, if someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.

NOTES: Do not share this medication with others.Laboratory and/or medical tests (e.g., serum potassium levels, complete blood count, hematocrit, vitamin B12 levels) should be performed to monitor your progress or check for side effects. Consult your doctor for more details.This product is not a substitute for a proper diet. Remember that it is best to get your vitamins from healthy foods. Vitamin B12 is commonly found in many foods from animals, especially liver, kidney, fish and shellfish, meat, and dairy foods.

MISSED DOSE: If you miss a dose, use it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Use your next dose at the regular time. Do not double the dose to catch up.

STORAGE: Store the pump upright at room temperature away from light and moisture. Do not freeze. Do not store in the bathroom. Discard the pump after you have used the labeled number of doses on the product package. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Information last revised August 2021. Copyright(c) 2021 First Databank, Inc.

IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

Is Taking Too Much Vitamin B-12 Dangerous?


If your B-complex contains 50,000% of the Daily Value (DV), which is 6 mcg for adults, then it has 3,000 mcg of B-12. For people without a severe B-12 deficiency, this is much more than necessary. [Note: In 2016, the FDA lowered the Daily Value for B-12 to just 2.4 mcg for most adults, but this won’t be reflected on all supplement labels until 2021. This means that your supplement actually provides 125,000% of the current daily requirement.]

Although no “Upper Tolerable Intake Level” has been established, there are risks associated with getting too much B-12 from supplements. At a dose of 500 mcg (one-sixth the amount in your supplement), an increased risk of colorectal cancer was reported in a placebo-controlled study of older people. Doses of just 20 mcg per day or higher have caused outbreaks of acne and rosacea. A high-dose B complex supplement (with 1,000 mcg of B-12) hurt, rather than helped, people with type 1 or type 2 diabetes and advanced kidney disease, resulting in a worsening of kidney function and an increase in the risk of heart attack, stroke and death.

In women who are pregnant, excessive blood levels of vitamin B-12 have been associated with an increased risk of autism in their children.

Taking some B-12 is advisable for people over the age of 50 (when you’re less able to extract B-12 from food), as well as for those taking medications that interfere with B-12 absorption (such as Prevacid, Prilosec and metformin), strict vegetarians, alcohol and drug abusers, people recovering from surgery or burns, and those with bowel or pancreatic cancer. But the amount needed to avoid deficiency is small and nowhere near the amount in the supplement you describe in your B-complex.

If you decide to take a B-12 supplement, you may want to choose one that has the right dose for you and has been tested and Approved by ConsumerLab.com. Be aware that sublingual and dissolvable B-12 supplements often contain sugar substitutes that can cause gas, bloating, and diarrhea in some people — particularly if taking multiple pills. You can use the Ingredients listings in CL’s Review to spot and avoid these ingredients.

In general, it’s best to avoid excessive doses of any vitamin if it is not needed.

Get more information, including the Recommended Daily Allowance for B-12 (by age and gender), differences in the forms of B-12, potential side-effects and drug interactions, plus ConsumerLab.com’s tests of popular products, in the B Vitamin Supplements Review >>

You can check the recommended intakes of other vitamins and minerals here.

Does Vitamin B12 Have Side Effects?

Side effects are possible for any food, supplement, or medication, and everyone reacts differently to different products. Vitamin C, for example, may promote loosening of the bowels if taken in excess, and too much niacin (B3) may cause a disagreeable flushing. Experiencing unpleasant side effects of a supplement is by no means enjoyable, and it’s best for consumers to do their research before diving into any supplement approach. Generally, the worst side effects for vitamins – including B vitamins – are diarrhea, nausea, rashes, and vomiting. [1] Does vitamin B12 have any side effects? Here’s what you need to know.


Let’s quickly give a brief overview of how vitamin B12 is absorbed. High doses of vitamin B12 have a low absorption rate when taken orally. To survive the digestive process, B12 must connect with intrinsic factor before it can enter the system. The amount of B12 that does get absorbed is directly related to the amount of intrinsic factor available. [2] Oral ingestion of large amounts of B12 is highly unlikely to cause an issue, as not all B12 survives this process. Even sublingual absorption (absorption through tissues of the mouth) doesn’t reach levels which would be of cause for concern.

Symptoms of Deficiency

Deficiency can result for a couple of reasons. Inadequate dietary consumption of foods containing B12 such as red meat, fish, or dairy products – an issue for many vegetarians and vegans – can lead to deficiency. An inability to digest B12 as a result of low levels of intrinsic factor – for either genetic reasons or a result of physical damage to the stomach or small intestine – can also cause deficiency.

Common symptoms include numbness in the hands and feet, moodiness, memory concerns, dementia, poor red blood cell formation, impaired DNA function, and fatigue.

B-12 Side Effects

B-12 occurs naturally in three forms: methylcobalamin, adenosylcobalamin, and hydroxocobalamin. Cyanocobalamin was created years ago in a lab using cyanide as a means for stabilization, and many low-quality supplements include this form. Injections are commonly used for individuals suffering from an inability to digest and absorb B12. Many individuals who have chosen a vegetarian or vegan lifestyle become B12 deficient as a result of eliminating natural dietary sources; still, many meat eaters today are also surprisingly deficient.

Some side effects have been reported for patients receiving cyanocobalamin injection. These include itching, acne, nausea, diarrhea, vascular thrombosis, headache, nervousness, and dizziness. Based on studies involving individuals, it appears 1 mg of cyanocobalamin via injection does not create any notable side effects. [3]

No Upper Limit Safety Recommendations Exist

No adverse or toxic reactions for vitamin B12 have occurred in individuals through dietary consumption or supplement use. The US Food and Nutrition Board have not established any upper safety limits for B12 in healthy people. Although you should always check with your doctor before starting a new supplement routine, supplementation with B12 is considered safe. If you’re in the market for a safe, natural B12 supplement, I highly recommend Global Healing’s own B12. It’s a vegan-safe formula that contains methylcobalamin and adenosylcobalamin, but also contains hydroxocobalamin for long-lasting, sustained support with 5,000 mcg of B12 per serving. It even contains Energized Trace Minerals™ for amplified bioavailability.