Vitamin B complex typically includes six B vitamins: B-1,B-2, B-3, B-5, B-6 and B-12. Some may contain more or fewer, depending on the brand. The amount of vitamin B in complex supplements varies dramatically. You might get as little as 10 percent of the recommended daily allowance for one B vitamin and more than 6,000 percent of the RDA for another. For safety's sake, do not take vitamin B supplements that exceed the highest daily value for each vitamin.
Vitamin B Deficiencies
If you eat a well-balanced diet that includes animal products, you may not need to take any amount of vitamin B complex. Vegans, persons older than 50 and people with medical conditions such as Crohn's disease and pernicious anemia may benefit from taking vitamin B-12 supplements. Women who take birth control pills may become deficient in vitamin B-6. Pregnant and breastfeeding women may need B complex to meet their extra needs. The prenatal vitamins prescribed by your doctor should handle your increased need. Persons who drink excessive amounts of alcohol may become deficient in one or more B vitamins. If you don't need vitamin B, taking supplements might pose more harm than benefits.
Vitamins B-1 and B-2
The RDA for vitamin B-1, found naturally in foods such as meat, nuts and cereal grains, ranges from 1 mg to 1.5 mg. Higher daily values of up to 30 mg a day can treat mild B-1 deficiencies, and you can take as much as 300 mg a day to treat severe B-1 deficiencies. You may experience skin irritation or, rarely, an allergic reaction if you take B-1. The highest daily allowance for treating a vitamin B-2 deficiency ranges from 5 mg to 30 mg a day. Taking extra vitamin B-2 might give you diarrhea, turn your urine orange and increase your urine output.
Vitamins B-3 and B-5
Unless you suffer from a vitamin B-3 deficiency or have been prescribed high doses by your doctor to treat conditions such as high cholesterol or Type 1 diabetes, you do not need to include more than 14 mg to 16 mg -- the RDA -- of vitamin B-3 in your diet. The highest daily value of vitamin B-3, also known as niacin, for persons with mild deficiencies ranges from 50 mg to 100 mg a day. You can take up to 500 mg a day to treat a severe deficiency. If you're not deficient in vitamin B-3, taking more than you need puts you at risk for serious side effects, including stomach ulcers, gout and liver damage. The highest daily value of vitamin B-5 -- pantothenic acid -- is 10 mg a day if you have a deficiency. The normal RDA ranges from 5 mg to 7 mg. Taking extra B-5 may give you diarrhea.
Vitamins B-6 and Vitamins B-12
You should not take more Vitamin B-6 -- pyridoxine -- than you need. Side effects include brain and nerve problems. The usual dose to treat a B-6 deficit ranges from 2.5 mg to 25 mg for up to 21 days and a maintenance dose of no more than 2.5 mg afterwards. If you suffer a B-6 deficiency because of birth control pill use, you may need to take as much as 25 mg daily. If you suffer from a vitamin B-12 deficiency, you can take 300 mcg to 10,000 mcg to improve your B-12 levels. Side effects of taking vitamin B-12 supplements include blood clots and diarrhea.
References
- University of Maryland Medical Center; Vitamin B 3 (Niacin); June 18, 2009
- Medline Plus: Thiamine (Vitamin B1); May 9, 2011
- Medline Plus; Riboflavin (Vitamin B2);Nov. 19, 2010
- Medline Plus:Pantothenic Acid (Vitamin B5); Nov. 19, 2010
- Office of Dietary Supplements, National Institutes of Health: Vitamin B6
- Centers for Disease Control and Prevention; Learn More about Vitamin B12 Deficiency; Aug. 3, 2009
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