Multivitamin Side Effects: Common, Severe, Long Term

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Medically reviewed by Drugs.com. Last updated on Mar 25, 2023.

Applies to multivitamin: oral capsule, oral liquid, oral tablet, oral tablet disintegrating. Other dosage forms:

• injection injectable, injection solution, oral capsule, oral elixir, oral liquid, oral tablet, sublingual liquid
• oral elixir, oral tablet, oral tablet extended release
• oral capsule, oral tablet
• oral tablet
• oral liquid, oral solution, oral tablet chewable
• oral capsule

Warning

If your product has iron in it:

• Accidental overdose of drugs that have iron in them is a leading cause of deadly poisoning in children younger than 6 years of age. Keep
  away from children. If this drug is taken by accident, call a doctor or poison control center right away.

Serious side effects of Multivitamin

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your
doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

All products:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing;
  tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue,
  or throat.

If your product has iron in it:

• Black, tarry, or bloody stools.
• Fever.
• Very upset stomach or throwing up.
• Very bad belly pain.
• Throwing up blood or throw up that looks like coffee grounds.
• Stomach cramps.

Other side effects of Multivitamin

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical
help if any of these side effects or any other side effects bother you or do not go away:

All products:

• Upset stomach or throwing up.

If your product has iron in it:

• Constipation.
• Change in color of stool to green.
• Diarrhea.
• Belly pain.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical
advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

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Professional resources

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Related treatment guides

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• Hyperhomocysteinemia

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer

Timespan and When to Be Concerned

Multivitamins are one of the most commonly used supplements in the United States — around one-third of adults currently take them (1).

People who take multivitamins often do so to improve or maintain their health, protect themselves against nutrient deficiencies, or simply make up for the odd nutrient gap in their diet (1).

You can purchase multivitamins without a prescription, and most people view them as safe, which might explain their popularity. Despite this, multivitamins are not risk-free.

This article discusses whether you should be concerned about taking multivitamins. It reviews the potential side effects of multivitamins and which ingredients may cause them.

Your body needs to consume at least 13 vitamins and 16 minerals regularly to function properly.

A well-balanced diet is the best way to obtain these nutrients. That said, multivitamins provide a good alternative source for those who are unable to meet their nutrient requirements through diet alone.

Multivitamins that provide up to 100% of the daily Dietary Reference Intakes (DRIs) are generally considered safe and often free of side effects, as long as you take them as directed.

Nonetheless, some people may still experience a few side effects when taking multivitamins. Some side effects are more common than others (2, 3).

Common side effects

Certain side effects are more likely to occur than others when you’re taking multivitamins. These include (2, 3):

• constipation
• diarrhea
• upset stomach
• nausea

These gut-related side effects are generally minor and often temporary. They tend to disappear as your body gets used to taking the multivitamin.

Nevertheless, contact your healthcare provider for further assistance if your symptoms persist.

Rare side effects

Rarer side effects of multivitamins include (2, 3):

• headaches
• nosebleeds
• insomnia
• gout

These typically occur very infrequently, especially if the dosage of nutrients in your multivitamin does not exceed the daily safe upper limit (UL).

However, people who combine multivitamins with other supplements or eat significant amounts of fortified foods may exceed the UL for certain nutrients. This may increase their risk of side effects (4).

Food companies sometimes add nutrients to foods during the manufacturing process. These are fortified foods.

Some people may also experience severe allergic reactions to certain multivitamins, although this is very rare.

If you notice hives, difficulty breathing, or swelling of the face, tongue, lips, or throat after taking a multivitamin, seek emergency medical help immediately.

Side effects in infants and children

Side effects in children are similar to those that adults may experience. However, children are likely to experience them at much lower doses than adults.

In other words, children who take multivitamins may have a higher risk of consuming extremely high levels of nutrients, which can lead to nutrient overdoses and even death in severe cases.

Companies market many multivitamins specifically for infants and children. However, a recent study suggests that up to 65% of them contain nutrient levels above the safe upper limits (UL) for children (5).

This may explain why experts report that children who consume multivitamins have a high risk of exceeding the UL, particularly for vitamin A, folic acid, and zinc (4).

Giving your child an iron-containing multivitamin when they don’t need it may also cause them to overdose on iron. Scientists consider this to be a lead cause of poisoning in children 6 years old and under (4).

To reduce the risk of side effects or toxic overdoses, make sure to consult your healthcare provider before giving your child a multivitamin.

Summary

Multivitamins are generally safe as long as they provide nutrient levels that fall within the DRI guidelines. Some people experience gut-related side effects when they first start taking a multivitamin, but these usually resolve quickly. Other side effects are rare.

The National Institutes of Health asserts that multivitamins providing nutrient levels that fall close to their DRI shouldn’t cause serious side effects. However, it’s important to note that the government doesn’t regulate multivitamins in the same way as it does medications (4).

This means there’s a risk that a multivitamin could contain higher levels of nutrients than its label states. Nutrient levels in some multivitamins may sometimes even reach or exceed the daily UL.

Others offer megadoses of certain nutrients that purposefully exceed the UL recommendations, capitalizing on some people’s belief that the more nutrients you ingest, the better the health effects.

Megadoses of some nutrients may not be particularly harmful, but extremely high doses of certain nutrients can seriously harm your health (4).

Nutrients to watch out for

Multivitamins generally contain three categories of nutrients:

• Water-soluble vitamins. These can dissolve in water and don’t usually accumulate in the body nor cause severe side effects if you take them in excess (e.g., B vitamins, vitamin C).
• Fat-soluble vitamins. These dissolve in fat and accumulate in the body, reaching toxic levels and potentially causing havoc if you take them in excess (e.g., vitamins A, D, E, and K).
• Minerals. These are inorganic elements that can accumulate in the body and sometimes cause harmful effects if you take them in excess (e.g., iron, iodine, zinc, copper, and selenium).

Some of these cause more side effects at higher dosages than others. The sections below highlight the nutrients from each category that may be particularly harmful if you take them at high doses.

Water-soluble vitamins

Excess intakes of water-soluble vitamins don’t typically cause severe side effects, even when intakes are close to the UL.

This is because your body tends to flush out excess intakes of these vitamins through your urine. Still, intakes that are several times over the UL may result in a variety of issues.

For instance, vitamin C intakes that are three times larger than the UL may cause cramps, diarrhea, nausea, vomiting, or migraines (6, 7).

Excess vitamin B3, also known as niacin, starting from intakes three times above the current UL may result in stomach pain, high blood pressure, vision problems, and liver damage (8).

Similarly, taking vitamin B6 at 10 times above the UL over the long term has been linked to skin lesions, light sensitivity, heartburn, and neurological problems (9).

Finally, excess intakes of vitamin B9, also known as folic acid, may weaken the immune system, cause neurological problems, and mask a severe vitamin B12 deficiency (10).

Fat-soluble vitamins

Multivitamins that offer large amounts of fat-soluble vitamins can be harmful, as excess levels of these vitamins can build up in the body.

For instance, excess intakes of vitamin A may cause headaches, liver damage, weaker bones, and birth defects (11).

Smokers and former smokers may especially benefit from avoiding multivitamins containing high amounts of vitamin A or beta carotene, which the body can convert into vitamin A. Getting too much of these nutrients may increase the risk of lung cancer (1, 4, 11).

Similarly, taking too much vitamin D, either due to manufacturing errors or taking an inappropriately high dosage, may result in nausea, vomiting, muscle weakness, cognitive problems, heart problems, kidney failure, and even death in severe cases (12).

Moreover, excess amounts of vitamin E may result in bleeding, diarrhea, weakness, blurred vision, and fertility problems (1, 13).

As for vitamin K, research has not found excessive intakes to cause too many problems. However, this vitamin can interact with various medications, including antibiotics and blood thinners.

People currently taking medications should let their healthcare provider know if they’re taking a multivitamin containing vitamin K (14).

Minerals

Like fat-soluble vitamins, minerals can accumulate in the body if you take them in excess, possibly causing harmful effects.

For instance, overly high intakes of certain minerals, such as iron, copper, magnesium, and zinc, can cause stomach upset, constipation, diarrhea, nausea, vomiting, stomach pain, and headaches (4, 15, 16, 17, 18).

Excess iron intake is particularly harmful because it may also cause liver problems.

For this reason, authorities advise adult men and postmenopausal women to avoid taking multivitamins that contain 18 mg of iron or more unless their healthcare provider advises them to do so (19).

Multivitamins containing high levels of iron, copper, and zinc may also prevent the body from absorbing other nutrients you consume (15, 16, 17).

Multivitamins containing too much iodine can cause thyroid problems. On the other hand, those with too much selenium may cause garlic-like breath, hair loss, brittle nails, or a metallic taste in the mouth (20, 21).

Selenium intakes above the UL may also cause severe neurological symptoms, kidney failure, and heart issues (21).

DRIs and ULs for each nutrient of concern

Most of the side effects mentioned in this article occur after a person consumes nutrient amounts that exceed the current upper levels (ULs).

Every nutrient has a UL at which scientists believe it becomes toxic. Exceeding a nutrient’s UL can lead to an overdose and severe side effects, such as liver damage and even death.

The following chart outlines both the DRI and UL for each nutrient of concern for adults.

Specific recommendations for infants and children vary widely based on their age. You can find more information in these exhaustive nutrient tables (22).

	DRI for adult men	DRI for adult women	UL
Vitamin A	900 mcg retinol activity equivalents (RAE)	700 mcg RAE	3,000 international units (IU)
Vitamin B3 (niacin)	16 mg niacin equivalents (NE)	14 mg NE	35 mg*
Vitamin B6 (pyridoxine)	1. 3 mg	1.3 mg	100 mg
Vitamin B9 (folate)	400 mcg dietary folate equivalents (DFE)	400 mcg DFE	1,000 mcg*
Vitamin C	90 mg	75 mg	2,000 mg
Vitamin D	600 IU	600 IU	4,000 IU
Vitamin E	15 mg	15 mg	1,000 mg*
Vitamin K	120 mcg	90 mcg	No UL established
Copper	900 mcg	900 mcg	10,000 mcg
Iodine	150 mcg	150 mcg	1,100 mcg
Iron	10 mg	18 mg	45 mg
Magnesium	420 mg	320 mg	350 mg*
Selenium	55 mcg	55 mcg	400 mcg
Zinc	11 mg	8 mg	40 mg

*Applies only to synthetic forms from supplements, fortified foods, or a
combination of the two.

It’s important to note that there’s no DRI available for folic acid, the synthetic form of vitamin B9 that you can find in multivitamins.

The form of vitamin B9 in the table above is called folate, and you can get it from natural sources — not multivitamins.

However, studies have found that dosages of the synthetic folic acid of more than 1,000 mcg per day may be associated with a range of negative health consequences in several populations (23, 24, 25).

Currently, researchers don’t fully understand the effects and safety of long-term intakes of vitamin or mineral dosages that fall between the DRI and UL. Therefore, scientists need to do more research on this topic.

Until more is known, it’s likely safest to avoid supplements that offer nutrient levels that exceed their DRIs.

Summary

Consuming multivitamins that contain nutrient levels exceeding the daily UL may result in an array of side effects. Scientists need to conduct more research to evaluate the effects of nutrient intakes that fall between the DRI and UL.

Multivitamins may also become contaminated with harmful compounds, such as arsenic or lead (26, 27).

When you ingest these harmful compounds in large amounts or over a longer period of time, they may cause a variety of health issues, including physical, muscular, and neurological problems, as well as birth defects (26, 28).

It’s impossible to identify whether a multivitamin contains these harmful compounds by looking at its label alone.

However, some manufacturers opt to get their supplements verified by third-party labs, which can confirm whether they’re free of contaminants and that they truly contain what the label states.

Some examples of independent supplement testing companies include ConsumerLab, NSF International, and U.S. Pharmacopeia.

Summary

Multivitamins can become contaminated with harmful compounds, such as arsenic or lead. To minimize this risk, consider choosing multivitamins that a third-party lab has independently tested.

Depending on the nutrient and its dosage, some side effects may occur very quickly, while others may take a longer time to develop (11).

For instance, taking a very high dose of one or multiple nutrients may cause gut symptoms that generally develop shortly after taking the supplement (15, 16, 17).

However, more severe side effects may develop over time as excess amounts of nutrients or unwanted contaminants gradually accumulate in the body. These longer-term side effects may include birth defects and liver, heart, and cognitive issues (11, 20, 21, 27, 28).

If you think you’re experiencing any side effects, make sure to bring them up with your healthcare provider as promptly as possible.

Summary

The speed at which you may experience side effects depends on the type and dosage of nutrient you consumed. Make sure to discuss any side effects with your healthcare provider as soon as you notice them.

Multivitamins can be helpful for those who are unable to reach their daily nutrient needs through diet alone.

However, multivitamins cannot replace a balanced diet, and taking them in high amounts may result in side effects ranging from mild stomach upset to severe liver and heart problems.

Like many supplements, multivitamins are not strictly regulated and may contain much higher levels of nutrients than the label states. Depending on the nutrient, this will influence the speed and severity at which you may experience side effects.

You can minimize your risk by only taking multivitamins when you truly need them. Opt for ones that contain nutrient levels close to the current DRIs and have been tested by a third-party lab.

Multivitamins: Benefits and Side Effects | Sheba Hospital

Simply put, a multivitamin is a dietary supplement that includes a combination of vitamins and sometimes minerals. Are vitamins helpful? So why not buy a multivitamin then?

The catch is that there is no clear standard for multivitamins, and therefore their composition and quality can vary greatly.

Originally designed to fill nutritional deficiencies in insufficient food intake, over time, multivitamins have been used for other purposes. There are now specially formulated formulas to boost performance, help with weight loss, protect against cancer and other diseases, and extend life. Do multivitamins really have all these miraculous properties, or is it just a big marketing game.

Natural vs. synthetic vitamins

Vitamins can be conditionally divided into two large groups: natural vitamins (found in natural, whole foods) and synthetic (laboratory-created). You don’t have to be a technologist to understand that what is synthesized in the laboratory is not necessarily different from what is found in nature. However, it happens differently – for example, synthetic vitamin E differs in its structure from natural.

An argument in favor of natural vitamins is the fact that their synthetic counterparts, including chemical distillates, are not recognized and used by the body in the same way as nutrients derived from whole foods.

Vitamins are not pre-tested

The main safety issue with multivitamin use is the possible toxicity from an overdose of one or another vitamin or mineral. For example, excessive consumption of zinc interferes with the absorption of copper and iron.

Because people don’t need to consult a doctor before taking supplements, they can take vitamins that interact with each other in ways that not only don’t help, but actually harm your health. In addition, there is always a risk of contamination of the product in case of non-compliance with the norms of its production.

Long-term benefit of multivitamins has not been proven

A diet high in fruits and vegetables reduces the risk of diabetes, cancer, heart disease and many other diseases. The high concentration of antioxidants and fiber is thought to reduce inflammation and protect against chronic disease. Accordingly, a natural continuation of this is the belief that antioxidants and vitamins synthetically isolated from vegetables and fruits have the same properties.

However, research on the benefits and harms of vitamin supplements is extremely inconsistent. Adding a nutrient to the diet can only be beneficial if the person is deficient in it. This is obvious, but does not answer the main question: can vitamins increase our productivity or extend our lives?

Multivitamin Recommendations

Research on multivitamins is generally lacking, and even studies on individual vitamins have yielded inconsistent results. So how to be?

Ideally, a person should strive to consume as many fresh vegetables and fruits as possible (10 servings) each day. Hardly anyone will disagree that this is the best way to get nutrients, replenish energy, increase productivity and protect against disease. Of course, the synergistic effect on health depends on the composition of vegetables and fruits. Regardless of what we know about vitamins, and what we do not know, most likely, nature has created natural foods according to the optimal formula. The only problem is the long-term implementation of such a diet.

This is especially true for people who are trying to limit their calorie intake in order to lose weight. After all, 10 pieces of fruit is 1000 calories per day. So how do you eat only the most useful?

The creators of multivitamins will tell you that they are multivitamins. The creators of nutritional supplements will say that synthetic vitamins are not absorbed by the body, so it is better not to take them. Unfortunately, there is no clear answer that would be scientifically confirmed yet.

In this way, the problem of the synthetic origin of vitamins can be circumvented, as well as the idea that in real food nutrients are present in combinations that are difficult to reproduce in the laboratory. If for some reason you can’t take concentrates, whole food vitamins are the next best option.

It is very important to carefully read the label of the product you are about to buy. Very often under the label “whole food vitamins” synthetic compounds are hidden in combination with yeast.

Traditional multivitamins are best avoided. However, if you exercise intensively or eat irregularly, you may be better off taking traditional dietary supplements. In this case, it is worth choosing a product that more accurately mimics the composition of ordinary food.

Thus, it is ultimately up to the individual to take a multivitamin or not, depending on their individual circumstances and needs. For most people, and especially for athletes and people working on their body shape, whole food vitamins will be the best choice.

Why vitamins are dangerous – 5 side effects

Alina Vishnevskaya

News editor

Often, in order to make up for the lack of nutrients in the body, people begin to take various multivitamins. However, their abuse can not only not give the desired effect, but even harm health.

Reported by eatthis.com.

See also:

Read also: A nutritionist called the most harmful potato dishes: do not eat it

What research says about multivitamins

For example, Johns Hopkins University researchers concluded that multivitamins do not reduce the risk of heart disease, cancer, or early death. In addition, they pointed out that vitamin E and beta-carotene supplements are harmful, especially at high doses.

Experts note that a healthy person probably does not need to take a multivitamin. If there is a nutritional deficiency or disease, then MD Ilene Ruhoy advises the use of specific supplements, having coordinated everything with your doctor.

In general, nutrition experts say that the best way to get your vitamins is from fresh fruits and vegetables.

The dangers of daily multivitamin intake

Nutritionists and doctors recommend not to spend money thoughtlessly on multivitamins, because addicting to them can have serious consequences.

1. Overdosing on certain vitamins

Taking a multivitamin, Dr. Đorđević notes, gives your body an unnatural cocktail of vitamins that would normally not be available in such a high concentration.

An overdose of certain vitamins, particularly A, D, K, or E, can have serious and life-threatening consequences. Side effects of excessive vitamin A intake include blurred vision, poor appetite, hair loss, headache, and sensitivity to sunlight. An overdose of vitamin D can cause weakness, fatigue, nausea, drowsiness, and loss of appetite. A daily intake of vitamin E without any deficiency can lead to blood thinning, which can cause problems with blood clotting and bleeding.

2. Dangerous interactions with drugs

If a person is taking any medication for a particular disease, then its combination with multivitamins can have a dangerous interaction.

For example, notes Melissa Neaves, PhD, people taking the anticoagulant drugs Warfarin should be careful with vitamin K supplements because it can interfere with their medication.

3. Influence of heavy metals

Many common multivitamins contain many heavy metals. They can accumulate in the body and lead to various problems. Therefore, experts advise choosing proven supplements to be sure that you are getting exactly what you need.

4. Additional problems in patients

Medicines and certain medical conditions can cause problems with multivitamins. So, nutritionist Amanda A. Kostro Miller notes that, for example, in the case of kidney disease, the body may experience more problems with the removal of nutrients.

5. The Overrated Benefits of Multivitamins

Ilene Ruhoy, MD, notes that the vast majority of people do not need to take multivitamins. If you do add them, then in a minimal amount, but it is better to get them from bioavailable sources – food. “ Vitamins and nutrients from food is the form our body prefers, not encapsulated with excipients,” she adds.

Other health materials

• One of the healthiest foods in the diet is fish. This is because it contains a large amount of nutrients. In particular, vitamin D and omega-3 fatty acids.
• Often, in pursuit of slim figures, people prefer low-fat yoghurts.