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Question:
Can taking too much vitamin B-12 be dangerous? The label on my B-complex states it contains 50,000% the Daily Value!

Answer:
If your B-complex contains 50,000% of the Daily Value (DV), which is 6 mcg for adults, then it has 3,000 mcg of B-12. For people without a severe B-12 deficiency, this is certainly more than necessary.  [Update: In 2016, the FDA lowered the Daily Value for B-12 to just 2.5 mcg for adults, but this won't be reflected on most supplement labels until 2018 or 2019.]  

Taking some B-12 is advisable for people over the age of 50 (when you're less able to extract B-12 from food), as well as for those taking medications that interfere with B-12 absorption, strict vegetarians, alcohol and drug abusers, people recovering from surgery or burns, and those with bowel or pancreatic cancer.  

Although vitamin B-12 is generally considered to be safe, and no "Upper Tolerable Intake Level" has been established, there are some reports of doses of 20 mcg per day or higher causing outbreaks of acne and rosacea. There is also a study which showed that a high-dose B complex supplement (with 1,000 mcg of B-12) hurt, rather than helped, people with type 1 or type 2 diabetes and advanced kidney disease, resulting in a worsening of kidney function and an increase in the risk of heart attack, stroke and death.  

If you decide to take a B-12 supplement, you may want to choose one which has been tested and Approved by ConsumerLab.com. Be aware that sublingual and dissolvable B-12 supplements often contain sugar substitutes which can, in some people, cause gas, bloating, and diarrhea -- particularly if taking multiple pills. You can use the Ingredients listings in CL's Review to spot and avoid these ingredients.

In women who are pregnant, excessive blood levels of vitamin B-12 have been associated with an increased risk of autism in their children. 

In general, it's best to avoid excessive doses of any vitamin if it is not needed.

Get more information, including the Recommended Daily Allowance for B-12 (by age and gender), differences in the forms of B-12, potential side-effects and drug interactions, plus ConsumerLab.com's tests of popular products, in the B Vitamin Supplements Review >>

You can check the recommended intakes of other vitamins and minerals here.

Also see these related CL Answers:

I thought the B vitamins were all water soluble and did not build up in the body, so you would not build up toxic levels. Am I wrong? >>

Being over 50 years old, I'm looking to take a vitamin B-12 supplement. I see that many contain a form of vitamin B-12 called cyanocobalamin, yet I read on the Internet that this form is toxic. Should I be concerned? >>

What B-vitamin complex do you recommend for older people? >>

What's the best way to take vitamin B12? >>

Is sublingual vitamin B-12 really better than the pill form? >>

Are B12 injections "better" than oral supplements? Are they necessary if I have a B12 deficiency? >>

Do vitamin B12 patches, like those from PatchMD, really work? >>

I read on your website that some B-12 vitamins can cause diarrhea due to added sugar substitutes like sorbitol. I have had diarrhea and never thought it could be caused by my vitamin B-12 supplement, until I read your article and stopped taking the supplement. My diarrhea stopped immediately. Can you help me find a brand of B-12 that doesn't contain sorbitol or sugar substitutes that could cause this problem? >>

Which foods are a good source of B vitamins? >>


See other recent and popular questions >>
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This CL Answer initially posted on 12/10/2014. Last updated 8/7/2017.
ConsumerLab.com members may submit questions to CLAnswers@ConsumerLab.com. We read all questions and try to answer those of popular interest.

 
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