How Much Vitamin B Complex is Safe to Take in a Day?

Tip

While personal vitamin needs vary from person to person, you shouldn't get more than 100 percent of the RDA from your vitamin B complex.

Recommended Dietary Allowances

The RDAs, established by the Institute of Medicine, are based on sex and age and should only be used as a guideline. Certain medical conditions or lifestyles may influence the recommended amount of vitamins you should take.

Men need 16 milligrams of niacin, 1.2 milligrams of thiamin and 1.3 milligrams of riboflavin, while women should have 14 milligrams of niacin, 1.1 milligrams of thiamin and 1.1 milligrams of riboflavin. Talk to your doctor if you're pregnant or nursing, because you may need more of each nutrient.

Read more: What Are the Benefits of B-Complex Vitamins?

Tolerable Upper Intake Levels

The tolerable upper intake level is the maximum amount of a vitamin or mineral you can take without running the risk of experiencing unpleasant side effects.

Although it may be beneficial to take more than the recommended dietary allowance of certain vitamins, you should never take more than the tolerable upper intake level unless specifically instructed by a doctor to do so.

Some B vitamins, such as vitamin B12, thiamin, biotin, pantothenic acid and riboflavin, don't have tolerable upper intake levels. This means that you're unlikely to experience adverse reactions when taking these vitamins, even if you take high doses.

However, folate, vitamin B6 and niacin do have a tolerable upper intake levels. Getting more than 1,000 micrograms a day of folate, 35 milligrams a day of niacin or 100 milligrams a day of vitamin B6 may cause unpleasant side effects. Avoid taking a vitamin B complex supplement that contains more than these amounts.

Getting Too Much

The most common side effects of taking too much of a vitamin B complex include diarrhea and abdominal cramps. More serious side effects include tingling or redness of the skin and nerve damage.

The folic acid in the supplement may also mask a vitamin B12 deficiency or may trigger a seizure in patients taking anticonvulsant medications when taken in excess.

High doses of these supplements may also negatively interact with certain medications. If you think that you've consumed too much vitamin B complex and are having any unusual symptoms, call your doctor for advice.

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