Most people get enough B vitamins through diet, but deficiencies sometimes can occur. The amount of B complex you need to correct a deficit depends on which B vitamins you lack. Not all vitamin B complex supplements contain the same ingredients and the amount of each vitamin may differ dramatically between brands. If you can't find a B complex supplement that meets your needs, you could take individual B vitamins instead. Talk to your doctor to help ensure that you get enough -- but not too much -- B vitamins.
Vitamins B1 and B2
If your diet includes foods such as meat, nuts, beans and cereal grains, you may obtain the recommended daily allowance -- 1 mg to 1.5 mg -- of B1 without having to take a supplement. If you don't get enough B1, or thiamine, you can treat a mild deficit by taking 5 mg to 30 mg a day. Treatment for severe B1 deficiencies may include up to 300 mg a day. Meats, eggs, nuts and green vegetables supply vitamin B2, or riboflavin. If you are deficient in vitamin B2, the recommended dose ranges from 5 mg to 30 mg daily. Side effects of taking extra vitamin B1 include skin irritation. Side effects of taking vitamin B2 include diarrhea, dark urine and increased urine output.
Vitamins B3 and B5
Deficiencies of vitamin B3 -- niacin -- prove rare, except among persons who abuse alcohol. The amount of B3 needed to treat mild deficits ranges from 50 mg to 100 mg daily. Persons with pellagra, a severe form of B3 deficiency, may take up to 500 mg a day. If you don't need extra B3 to alleviate a deficiency, taking high doses of more than 100 mg a day puts you at risk for serious side effects such as vision loss, intestinal tract ulcers and liver damage. The usual recommended daily allowance for vitamin B5, also called pantothenic acid, ranges from 5 mg to 7 mg. Deficits may require that you take up to 10 mg a day. You may experience diarrhea when taking B5.
Vitamin B6
If you suffer from a vitamin B6, or pyridoxine, deficiency, your health care provider may suggest a supplemental dose between 2.5 mg to 25 mg a day for up to three weeks, followed by a maintenance dose of up to 2.5 mg a day. Women can suffer a vitamin B6 deficiency if they use birth control pills and may need to take up to 30 mg a day. If you don't need extra B6, taking a supplement poses serious risks that include possible nerve and brain problems.
Vitamin B12
About one in 31 adults older than 50 suffer from a vitamin B12, or cyanocobalamin, deficiency, reports the Centers for Disease Control and Prevention. Other persons vulnerable to vitamin B12 deficits include vegans -- only animal products provide reliable sources of vitamin B12 -- and anyone who's undergone stomach surgery. If you're anemic or have Crohn's disease, you may also suffer a vitamin B12 deficit. Untreated, vitamin B12 deficiencies may lead to permanent nerve damage. To treat a deficit, take 300 mcg to 10,000 mcg daily. If you take more vitamin B12 than you need, possible side effects to watch for are blood clots and diarrhea.
References
- University of Maryland Medical Center; Vitamin B3 (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
- Medline Plus: Pyridoxine (Vitamin B6); Dec. 13, 2010
- Medline Plus: Cyanocobalamin (Vitamin B12); April 4, 2011
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