Vitamin B12 is great. It helps form red blood cells. It is crucial to the synthesis and repair of DNA and the myelin sheath, a layer safeguarding our nerves. It also aids optimizing our homocysteine levels, decreasing our risk of blood clotting and heart attack. But can we actually have too much B12?
That’s what this post is about.
Can too much vitamin B12 hurt you? Can it not? Is vitamin B12 toxicity a scary possibility, or can we just continue injecting ourselves with huge doses with no mercy? Here’s everything you need to know about vitamin B12 overdose.
Vitamin B12 Overdose Symptoms & Side Effects
Can you take too much B12?
Short answer: No.
Certain vitamins can harm you when taken in excess, specifically fat-soluble vitamins like A and K which will build up in your fat stores. Vitamin B12, however, is water soluble and will be flushed out in your urine if taken in excess. Therefore, there are no vitamin B12 overdose symptoms.
The recommended daily dose is very low, about 2-3µg, yet many supplements deliver hundreds or thousands of µg per dose. This is no mistake. There’s a reason no upper limit for B12 has been set by The Food and Nutrition Board.
Consider this:
B12 (the methylcobalamin form) has been used in ultra-high doses (25 to 50 thousands of µg doses!) to prolong survival of ALS patients and aid patients with peripheral neuropathy and chronic axonal degeneration. It is also used in huge amounts to detoxify cyanide poisonings.
We’re talking here about 25,000 or 50,000µg doses. That’s more than 10,000 times higher than the recommended daily limit, yet it still causes no excess vitamin B12 toxicity symptoms.
Summary: Can You Have Too Much B12?
Can you overdose on B12?
No.
No matter if you inject yourself or consume a ton of vitamin B12 foods every day, any vitamin B12 excess will be excreted in your urine. My point?
Don’t worry, and enjoy the benefits of B12.
This article is part of a larger guide: Vitamin B12.
Thank you for the information sir. But can you take too much vitamin b12 — not because of toxicity — but because of excess b12 wasted through the urine? Supplements aren’t cheap where I come from, and I’m afraid to taking too much b12 vitamin doses and getting the same effectiveness as if I took smaller doses. Your advice appreciated.
Yes, absolutely. While vit B12 toxicity is no issue, you can get wasteful with your supplementation. That’s why I recommend smaller, more frequent doses instead of large weekly doses (for example, daily 1,000mcg instead of weekly 10,000mcg doses, especially with injections — which are already less wasteful than any other form of B12). This will help you get less excess of vitamin B12 in your urine.
Someone at my hosptal has a rare condition of too much b12. They are trying to figure out why. Any answers
I read in the Mayo Clinic web site that B12 is stored in the body and can cause symptoms when too high.
High doses of vitamin B-12, might cause:
Dizziness
Headache
Anxiety
Nausea
Vomiting
Hey Renee,
I hope you will read this :) I just read your reply about someone lying in the hospital with a rare condition of havin too high levels of B12? Do you know the name of that condition? 2,5 years ago I had a B12 “intoxication”: 1 week after taking quick-melt tablets I collapsed and had about 40 symptoms. Before that week I felt alive and healthy for about 95% and after that 1 week of B12 tablets (high dosis tablets) I felt scarcely alive. For 1,5 years I was afraid I would die from that condition. I’m still not sure what happened and why that high dosis of B12 cause these extremes symptoms for me. Thanks.
Hello, I’m also interested to find out more about this condition. I had a severe reaction a little over a year ago. Broke out in a rash that got worse over the days and severe itching and pain. Long story short after visits to my general doctor then dermatologist, no one could figure out what was causing this. It got so bad I ended up in the ER. I asked about B vitamins but was told not possible to have this kind of reaction. It wasn’t until I stopped taking my B vitamin supplement did the rash start to clear up. A year and a half later and I still notice sensitives when having energy drinks or if I try to take a multivitamin
What if I’m pregnant? Can you overdose on vitamin b12 if your’e pregnant? thanks!!!!! Please answer fast.
There are no side effects of too much b12 whatsoever. You should be more worried about not having enough B12 — rather than too much — when pregnant. It is extremely important for the development of your child.
Have an easy, safe pregnancy.
Hi,
I recently contracted shingles and decided to take high doses of Vitamin B12 sublingual and also an injection. Following this input of Vitamin B12, I have experienced severe numbness and muscle cramps in both legs, I am a fit runner and only mid 40’s. This has led me to believe that Vit B12 caused these leg symptoms…any comments appreciated.
Rob
Rob I have read that these symptoms were normal after a deficiency because it’s related to the nerves starting to heal. Just continue treatment and after a few weeks it will get better. See it like that: you had a problem but you weren’t feeling it, the body starts to correct the problem and as nerves are involved you suddenly just feel it more while it is getting better
Hi, just wondered if your symptoms have gone? I’m also experiencing numbness after b12 injections and no one is taking me seriously when I mention about side effects. No one replies or updates on here
Had to much b12. Stiff all over, numbing in hands and feet haven’t had a shot in 4 months. Feel like I’ve been ran over.
I too experienced this and much more. It is indeed possible to overdose on b12.
Hi, I accidently took a double dose of B12 vitamin pills, because I’m used to taking a lower dose. The next day my face and neck broke out in hives and has remained for 2 days. I looked this up, and this appears to be a side effect people experience.
I feel like it’s a discomfort worth noting, so people will be careful. Thanks.
Is methylcobalamin better than cyanocobalamin?
Yes, if you’re interested why read my article on methylcobalamin vs cyanocobalamin.
Please help I TOOK 1000 mcg for 10 days and I’m numb all over ..fatigue anxiety ..even my neck injury doesn’t hurt ..I think NERVE DAMAGE
Hi Emily,
Have your symptoms gone ? I’m experiencing the same
I disagree. I just discovered I am homozygous MTHFR and my doctor had my increasing my Methylcobolamin by 1000mcg every week. When I got to 400mcg, I had terrible headaches, my head felt like a balloon blowing up, and I developed hives, anxiety, and nausea. Yes, B12 can have side effects.
I WAS DIAGNOSED IN 2014 WITH CLL. SINCE THEN M Y b12 IS VERY HIGH AT 1200. IS THIS BECAUSE OF THE CLL? I THIS NORMAL?
Possibly you are not absorbing the B12. Or you may need a different form. Just a thought.
I have been taking 2000mcg of vit b12 pills a day for sciatic nerve pain and 300 mcg of vitb 6.
It has helped this pain ( doctor recomended. Bur for a week or so head pain, pressure and numbness, prickling on my face.
Any thoughts?
Check the other ingredients in the B12 supplements especially the liquid drops. Some of them have preservatives, potassium sorbate, food colorings, etc., that may be causing reactions if you have sensitivities.
Ina e been having B12 shots for many years and wonder if my itching on my arms and legs is caused by too much B12?
im a compound hetero for mthfr. my b12 levels are 4x the normal range. i was taking cyanocobalamin for years not knowing that it was actually bad for me. i have switched my b12 to hydroxy (since finding out about mthfr) since i also have vdr and comt mutations. how can i detox b12 so i can start using the good kind efficiently?
I’ve been taking methyl b complex and ended up with severe diarrhoea and optic neuritis. I had some unrelated health problems but was basically fine before I started taking it but apparently my liver needed ‘support’ according to a nutritionist. I’m pretty certain it’s the vitamin b complex as I had diarrhoea every day for a month while taking it and within 2 days of stopping it had completely gone back to normal, and my eye is getting better.
I think it’s dangerous to state there are absolutely no side effects from overdosing on a vitamin when the possibility of nerve damage and other symptoms from b vitamins are widely discussed on the internet and clearly many people have experienced them. At the very least, this article should advise people to confirm they have a deficiency before taking it.
I agree with you. After taking 2000 mcgs of b12 daily for 2 years I developed neuropathy in my feet, tingling and burning. My b12 level is 1200. I am going to stop taking it and hope the symptoms are reversed. I have been tested for everything else including diabetes and it comes up negative.
If you have a high b12 test and took a supplement is the test valid?
Hi! How much µicrograms are 2500 IU?
Can you overdose on B12 if it’s not Methylcobalamin you’re taking?