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Multivitamins effect: Timespan and When to Be Concerned

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.


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).


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 menDRI for adult womenUL
Vitamin A900 mcg retinol activity equivalents (RAE)700 mcg RAE3,000 international units (IU)
Vitamin B3 (niacin)16 mg niacin equivalents (NE)14 mg NE35 mg*
Vitamin B6 (pyridoxine)1. 3 mg1.3 mg100 mg
Vitamin B9 (folate)400 mcg dietary folate equivalents (DFE)400 mcg DFE1,000 mcg*
Vitamin C90 mg75 mg2,000 mg
Vitamin D600 IU600 IU4,000 IU
Vitamin E15 mg15 mg1,000 mg*
Vitamin K120 mcg90 mcgNo UL established
Copper900 mcg900 mcg10,000 mcg
Iodine150 mcg150 mcg1,100 mcg
Iron10 mg18 mg45 mg
Magnesium420 mg320 mg350 mg*
Selenium55 mcg55 mcg400 mcg
Zinc11 mg8 mg40 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.


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.


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.


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.

Is There Really Any Benefit to Multivitamins?

Half of all American adults—including 70 percent of those age 65 and older—take a multivitamin or another vitamin or mineral supplement regularly. The total price tag exceeds $12 billion per year—money that Johns Hopkins nutrition experts say might be better spent on nutrient-packed foods like fruit, vegetables, whole grains and low-fat dairy products.

In an editorial in the journal Annals of Internal Medicine titled “Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements,” Johns Hopkins researchers reviewed evidence about supplements, including three very recent studies:

  • An analysis of research involving 450,000 people, which found that multivitamins did not reduce risk for heart disease or cancer.
  • A study that tracked the mental functioning and multivitamin use of 5,947 men for 12 years found that multivitamins did not reduce risk for mental declines such as memory loss or slowed-down thinking.
  • A study of 1,708 heart attack survivors who took a high-dose multivitamin or placebo for up to 55 months. Rates of later heart attacks, heart surgeries and deaths were similar in the two groups.

Will a Daily Vitamin Help Keep Your Heart Healthy?

Is a daily vitamin necessary? Get the answer from Johns Hopkins physician Edgar Miller III.

The Vitamin Verdict

The researchers concluded that multivitamins don’t reduce the risk for heart disease, cancer, cognitive decline (such as memory loss and slowed-down thinking) or an early death. They also noted that in prior studies, vitamin E and beta-carotene supplements appear to be harmful, especially at high doses.

“Pills are not a shortcut to better health and the prevention of chronic diseases,” says Larry Appel, M.D., director of the Johns Hopkins Welch Center for Prevention, Epidemiology and Clinical Research. “Other nutrition recommendations have much stronger evidence of benefits—eating a healthy diet, maintaining a healthy weight, and reducing the amount of saturated fat, trans fat, sodium and sugar you eat.”

The exception is supplemental folic acid for women of child-bearing potential, Appel says. “Folic acid prevents neural tube defects in babies when women take it before and during early pregnancy. That’s why multivitamins are recommended for young women.” The Centers for Disease Control and Prevention recommends that all women of reproductive age get 400 micrograms of folic acid daily. The amount of iron in a multivitamin may also be beneficial for women of child-bearing potential, Appel adds.

“I don’t recommend other supplements,” Appel says. “If you follow a healthy diet, you can get all of the vitamins and minerals you need from food.”

What the Experts Do

Healthy Food Instead of Supplements

“I don’t take any supplements routinely,” says Larry Appel, M.D., director of the Johns Hopkins Welch Center for Prevention, Epidemiology and Clinical Research. “I try to eat three healthy meals a day to get the vitamins, minerals and other nutrients I need. ” How he does it:

  • Plenty of produce. “I aim for two or more servings of fruits or vegetables at every meal,” he says. “I enjoy salads and have one for lunch or dinner several times a week.”
  • Low-fat dairy and whole grains. “Low-fat or fat-free milk and yogurt provide calcium, magnesium, potassium and other nutrients,” he says. “I have cereal with milk for breakfast a few times a week. And I have yogurt sometimes too.”
  • Protein. “At home we usually have fish or chicken for dinner. I am not a vegetarian; rather, I eat minimal meat,” Appel says. Some fish, such as salmon, are a good source of healthful omega-3 fatty acids.


Whole grains: Grains such as whole wheat, brown rice and barley still have their fiber-rich outer shell, called the bran, and inner germ. It provides vitamins, minerals and good fats. Choosing whole grain side dishes, cereals, breads and more may lower the risk for heart disease, type 2 diabetes and cancer and improve digestion, too.

Saturated fat: A type of fat found in abundance in butter, whole milk, ice cream, full-fat cheese, fatty meats, poultry skin, and palm and coconut oils. Saturated fat raises levels of heart-threatening LDL cholesterol in your bloodstream. It can also interfere with your body’s ability to absorb blood sugar easily. Limiting saturated fat can help control your risk for heart disease.

Omega-3 fatty acids (oh-may-ga three fah-tee a-sids): Healthy polyunsaturated fats that the body uses to build brain-cell membranes. They’re considered essential fats because our body needs them but can’t make them on its own; we must take them in through food or supplements. A diet rich in omega-3s—found in fatty fish, like salmon, tuna and mackerel, as well as in walnuts, flaxseed and canola oil—and low in saturated fats may help protect against heart disease, stroke, cancer and inflammatory bowel disease.

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Half of American adults and 70% of those over 65 regularly take multivitamin and mineral supplements, spending about $12 billion a year on them.

It would be better to spend it on healthy foods that contain all the vitamins and minerals that a person needs in a natural form, such as vegetables and fruits, whole grains and low-fat dairy products, say Johns Hopkins University experts.

  • Why vitamin supplements don’t work and can be deadly
  • “Vitamin drips” in schools and hairdressers. Why are they dangerous?
  • Scientists: multivitamins are not needed during pregnancy

Multivitamins (or multivitamins) are preparations containing several vitamins, sometimes together with trace elements, in one capsule.

In an editorial in the Annals of Internal Medicine entitled “Enough: Stop Throwing Money on Multivitamin and Mineral Supplements,” they reported on the results of three studies they conducted. Here are the main findings:

  • Analysis of 450 thousand people shows that multivitamins do not reduce the risk of heart disease and cancer
  • Follow-up of 5947 men over 12 years showed that they do not reduce the risk of cognitive and memory degradation
  • Among 1708 people heart attack survivors, of whom one group took high doses of multivitamins for 55 months, and the other placebo, the number of repeated heart attacks, heart operations and deaths was about the same

Researchers have also found that vitamin E and beta-carotene supplements can be harmful, especially at high doses.

“Pills are not a shortcut to health and chronic disease prevention,” says Larry Appel, director of the Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins University. and salt.”

The exception is folic acid supplements for women of childbearing age, he points out. “Folic acid prevents neural tube defects in babies if the mother takes it before and in early pregnancy. Therefore, a multivitamin is recommended for young women.”

The Center for Prevention, Epidemiology and Clinical Research advises all women of reproductive age to take 400 micrograms of folic acid daily. The iron found in multivitamins can also be good for them, adds Larry Appel.

“I don’t recommend anything else,” he says. “If you eat a healthy diet, you’ll get all the vitamins and minerals you need from food.”

M.D. diet

Image copyright, Getty Images

“I don’t take any supplements,” said Larry Appel. for dinner”.

“Skim milk and yogurt contain calcium, magnesium, potassium, so I have whole grain porridge with milk for breakfast several times a week and often eat yogurt.”

“At home, we usually have fish or chicken for dinner, which contains the necessary proteins. I’m not a vegetarian, I just try to eat less meat. Some types of fish, such as salmon, are rich in healthy omega-3 fatty acids.”

Other advice and what Hopkins University scientists do not advise

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Whole Grains: Wheat, brown rice, and barley grains contain vitamins, minerals, and healthy fats. Whole-grain breads and cereals reduce the risk of heart disease, type 2 diabetes, and cancer, and improve digestion.

Omega-3 fatty acids: They are indispensable for the construction of brain cell membranes. The body does not produce them itself and must receive them from the environment. They are abundant in salmon, tuna, and mackerel, as well as nuts, flaxseed, and rapeseed oil. An appropriate diet reduces the risk of heart disease, stroke, cancer, and intestinal inflammation.

Saturated fat: Found in excess in butter, whole milk, full fat cheese, ice cream, fatty meats, poultry skins, palm oil, and coconut oil. Contribute to the accumulation of cholesterol in the vessels, adversely affect the absorption of sugar in the blood. Reducing the intake of saturated fat is a means of preventing cardiovascular disease.

However, it is possible that not everyone will agree with the recommendations of experts at Johns Hopkins University regarding the optimal diet. The views of some modern nutritionists and their conclusions about the benefits of a number of products, in particular, dairy, low-fat and cereals, differ from traditional recommendations.

Multivitamin complex – instructions for use, doses, side effects, reviews of the drug:


All forms of release, dosages, registration certificates, drug manufacturers, drug characteristics

Product description Multivitamin complex (tablets) based on the official instructions, approved by the manufacturer in 2008

Approval date: 12/28/2008


  • Active substance
  • ATX
  • Pharmacological group
  • Instruction
  • Storage conditions
  • Best before date
  • Reviews

Active ingredient

Multivitamins (Multivitamins)


A11JC Vitamins, combinations

Pharmacological group

Vitamins and vitamin-like products


Pharma action. Combined preparation, the action of which is due to the effects of the vitamins included in its composition.

Indications. Prevention of hypovitaminosis. Conditions accompanied by an increased need for vitamins: during the period of convalescence after serious illness, during periods of increased physical and mental stress, during pregnancy and lactation, malnutrition or unbalanced nutrition, reduction diets, to improve metabolism and general condition in the elderly and senile age (in part of complex therapy).

Contraindications. Hypersensitivity, hypervitaminosis A and D, children under 10 years of age.

Dosing regimen. Inside, after meals: adults – 1 tab. 3 times a day, children 11-14 years old – 2 tablets. per day. Tablets should be chewed and washed down with a small amount of liquid. The course of treatment is 20 days. If necessary, repeat the course after 2 months.

Side effects. Skin allergic reactions (urticaria).