A vitamin B complex supplement typically contains riboflavin, pantothenic acid, folic acid, niacin, biotin, thiamin, vitamin B-6 and vitamin B-12. Although most people get enough B vitamins through their diet, those with restricted or poor diets or those with certain medical conditions may benefit from taking a vitamin B complex supplement. Always talk to your doctor to determine if supplementation is appropriate for your situation.
All the B vitamins are water-soluble, which means excess amounts are excreted through your urine and not stored in the body. Because of this, some people mistakenly believe that taking too much of a water-soluble vitamin will not cause any adverse effects. While it is true that it is riskier to take high amounts of a fat-soluble vitamin, such as vitamin A or vitamin E, water-soluble vitamins may also cause adverse effects when taken in excess. To avoid consuming too much of any vitamin, it's wise to be aware of the recommended daily allowance of nutrients for your age and gender.
Recommended Dietary Allowances
The recommended dietary allowances, which are established by the Institute of Medicine, are based on gender and age and should only be used as a guideline. Certain medical conditions or lifestyles may influence the recommended amount of vitamins you should get. Generally speaking, most healthy adult men and women should consume approximately 2.4 mcg of vitamin B-12, 1.3 mg of vitamin B-6, 400 mcg of folate, 5 mg of pantothenic acid and 30 mcg of biotin. Men need 16 mg of niacin, 1.2 mg of thiamin and 1.3 mg of riboflavin, while women should have 14 mg of niacin, 1.1 mg of thiamin and 1.1 mg of riboflavin. Pregnant and nursing women should check with their doctor since they will require more of each nutrient.
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 B-12, thiamin, biotin, pantothenic acid and riboflavin, do not have tolerable upper intake levels. This means you are unlikely to experience adverse reactions when taking these vitamins, even if you take high doses. However, folate, vitamin B-6 and niacin do have a tolerable upper intake level. Getting more than 1,000 mcg a day of folate, 35 mg a day of niacin or 100 mg a day of vitamin B-6 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 a vitamin B complex include diarrhea and abdominal cramps. More serious side effects include a tingling or redness of the skin and temporary nerve damage to the limbs. The folic acid in the supplement may mask a vitamin B-12 deficiency or may trigger a seizure in patients taking anticonvulsant medications when taken in excess. Taking too much of a vitamin B complex supplement over time can lead to certain health issues, including skin problems, high blood sugar levels, heart problems, blurred vision, gout and liver problems, according to the American Cancer Society. High doses of these supplements may also negatively interact with certain medications. If you have consumed too much of a vitamin B complex and are having any unusual side effects, call your doctor for advice.