Are there any side effects from Vitamin B?

There are side effects to almost any vitamin if you ingest too much, but there are also side effects if you get too little. Side effects from high levels of B-vitamins, well above the RDA are very rare when taken orally. This is due to the fact that they are water soluble, which allows you to excrete excess amounts through urine. The B vitamins include: B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (Pantothenic acid), B6 (pyridoxamine), folic acid (B9) and cobalamin (B12). Validated adverse reactions to B vitamins are generally confined to vitamins B3 (niacin), B6 and injections of B1 (thiamine), although rare. These side effects can range from drops in blood pressure, disruption in nerve transmissions to rashes and skin flushing. In order to avoid side effects of B vitamins, make sure you stay within established safe/necessary ranges (see below) -- especially when taking vitamins B3 and B6. The goal is to make sure you get proper daily amounts of the necessary B vitamins unless advised otherwise by a qualified physician. This goal is accomplished by taking a daily multivitamin and mineral formula that contains the necessary B vitamins shown below.
  • B1: 2-30 mg/day
  • B2: 5-30 mg/day
  • B3 (Niacinamide): 30-50 mg/day
  • B6: 6-50 mg/day
  • Folic acid: 400-900 mcg/day
  • B12: 6-50 mcg/day
Side effects from B vitamins vary depending on which B vitamin you consume. Side effects generally occur only when you consume too much -- and it's very hard to overdose if you get your B vitamins from food. But you can get too much from supplements.

For example, consuming too much vitamin B3 (niacin) may cause skin flushing, rashes, stomach ulcers, or even liver damage. Excess amounts of vitamin B6 may lead to a lack of coordination or numbness. Too much pantothenic acid (vitamin B5) may cause diarrhea. Talk to your doctor if you think you might be experiencing side effects from taking levels of B vitamins that may be too high.

Continue Learning about Vitamins

Banned Ingredients Still Found in Supplements
Banned Ingredients Still Found in Supplements
Don’t believe everything you hear when it comes to health supplements. It’s important to sleuth out -- and avoid -- harmful products advertised on TV,...
Read More
When can taking vitamin supplements be dangerous to my health?
Stacy Wiegman, PharmDStacy Wiegman, PharmD
Taking vitamin supplements may be dangerous to your health if you overdo it, which can lead to p...
More Answers
8 Foods That Can Replace Your Multivitamin
8 Foods That Can Replace Your Multivitamin8 Foods That Can Replace Your Multivitamin8 Foods That Can Replace Your Multivitamin8 Foods That Can Replace Your Multivitamin
Skip the pharmacy and shop the produce department instead.
Start Slideshow
Why Do Some Vitamins Make Me Nauseous?
Why Do Some Vitamins Make Me Nauseous?

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.