Should You Take B12 Supplements if You Take Metformin?

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Metformin is the most widely prescribed medication to treat diabetes (usually type 2 diabetes) in the world. Its effectiveness equals or exceeds many of the other oral medications available and has an excellent safety profile for most individuals. However, for the last ten to fifteen years there has been a question as to whether metformin causes B12 deficiency in those who take the drug for long periods of time.

Several studies and clinical cases have noted suboptimal blood levels of B12 in those who have taken metformin for extended periods. The National Nutrition and Health Examination reviewed the blood work on 1,621 people with diabetes, more than a third of whom were taking metformin, and demonstrated a reduction in serum B12 levels in people who took metformin compared to those who did not.

But just because these people taking metformin had lower levels of B12 in their bloodstream doesn’t necessarily mean the B12 that’s there isn’t getting the job done. New measurements of B12 activity have indicated that although metformin does seem to reduce blood levels of B12, this may not reduce the vitamin’s effectiveness in carrying out it its functions in the body. When B12 doesn’t work the way it’s supposed to, levels of something called total plasma homocysteine (tHcy) go up. But newer studies looking at the levels of tHcy in people who take metformin have found that they have not been elevated.

According to an article published this year in Diabetes Care, “low serum B12 alone without disturbances in the metabolic markers has no diagnostic value.” From a practical standpoint, this means that if a B12 deficiency is suspected from a serum B12 test, further testing should be undertaken before assuming the patient is B12 deficient.

B12 is one of the B-family of vitamins that is important for the healthy development of blood cells , DNA and the nervous system. Although it is known as a water soluble vitamin, we can store vitamin B12 in the liver for up to one year. B12 is widely distributed in the diets of those who eat any animal products; although those following a vegan diet will need to consume a B12 supplement or B12 enriched tofu or yeast to obtain adequate amounts of the vitamin.

B12 deficiency can lead to megaloblastic anemia, a type of anemia in which the red blood cells are significantly larger than normal. People with mild B12 deficiency may feel weak or tired, bleed easily, experience tingling in the hands and feet and swelling of the tongue. Severe B12 deficiency can have serious effects such as memory loss, delusions, loss of taste and smell.

Metformin contributes to serum B12 deficiency by preventing its transfer into the blood through a calcium dependent membrane, leading to decreased absorption. In addition, in order for B12 o be absorbed into the bloodstream it needs an acid environment in the stomach. Age and intake of acid reducing medications, such as anti-acids or proton pump inhibitors increase the likelihood that older adults may suffer from a B12 deficiency as can certain gastrointestinal disorder such as atrophic gastritis and Crohns disease or surgical reduction of the stomach.

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20 Responses to Should You Take B12 Supplements if You Take Metformin?

  1. Actually, methylmalonic acid is a much better functional indicator of B12 deficiency than homocysteine, which is an indicator which best indicates the presence of MTHF type folate and the capacity for it to methylate methionine. MMA becomes Succinic acid which then enters the Krebs Citric Acid cycle, and the only nutrient cofactor which allows that is B12.

  2. BrittJ says:

    Citations, please…

  3. Nev Fronda says:

    So then we have to put patients on B12 supplements to avoid the symptoms? Especially elderly on long standing use of metformin?

  4. Nancy Camp says:

    Maybe not B-12, but suffer an extremely low amount of Vitamin D and have to take supplements.

    Nancy Camp

  5. Nancy Camp says:

    Suffer extreme loss of Vitamin D and must take supplements. I take Metformin

  6. Joydev Maity says:

    Is insulin effect on kidney disease?

  7. Angie says:

    I want to start taking b12 because I am on metformin now (not yet quite diagnosed with Type II. My a1c is 6). but mostly i am SO DOG TIRED from 2pm and on, that i am yawning at work and headachy and almost scared to drive home from work every day. I go home and cant do anything but lay in bed.
    How much b12 should I take per day? is it daily? Some websites say 6mcg. Some websites say 2500 mcg. So i have no idea! 6 or 2500?

  8. Charlotte says:

    Has anyone heard of Eligen B12? Apparently it’s a new prescription oral tablet I recently read about that works as well as the IM B12 injection, even if you don’t have intrinsic factor. Apparently it came out a month or two ago

  9. Kaye Seeton says:

    I was just disgnosed with Type 2 diabetes on May 7, 2015. Doctor started me on Metformin first but after a few days of gradually increasing until taking 500 mg x 2, 2times per day. Ended up getting sick and vomiting. Doctor changed to 30 mg Gliclazide in morning and 500 mg Metformin in evening until glucose is stabilized. He would prefer that I only take Metformin. Am also on Proton pump inhibitor, Rebeprozole. Am concerned about B12 becoming deficient. Doctor concerned about Gliclazide causing hypoglycemia. Since I am a newbie, would appreciate any advice or critique.

  10. Gefs says:

    Am on metformin for the last five yrs. @ 500mg/day.then i started taking b complex two yrs ago.until now i am taking b i have to continue taking b complex?though the tingling and numbness on my fingers stopped?…still on metformin.

  11. Robert says:

    Be sure to have serum B12 checked! If you decide to take oral B12 there is a company that has really impressed me with the quality and absorption rate of there vitamins. Over the last 18 years, a group of scientists and doctors created a one-of-a-kind nutritional supplement program that delivers personalized pharmaceutical grade nutrition, with your name on it, directly to your door.

    Pharmaceutical grade is the highest grade of supplements one can consume. Next would be Medical Grade i.e prescribed prenatal vitamins, then cosmetic grade i.e Centrum/One-a-Day. Pharmaceutical grade is usually a lot more expensive than cosmetic grade supplements but this company provides their nutrition at a fraction of the price of big box retail stores.

    You simply take a free, HIPAA compliant (confidential) online assessment answering questions about your diet, lifestyle, body type, physical condition, health goals, medications, etc. All of your supplement recommendations are backed by medical and scientific studies. At the end of your assessment you can review the medical research articles if you want. Click on the blue question marks. (??) Pretty cool!

    All supplements are 100% all natural, non-GMO, casein, soy and gluten Free. 30 Day Money Back Guarantee! Give the assessment a whirl! click the icon (Take Your Free Assessment Now!)

  12. Bambang Harymurti says:

    I am just starting taking 500 mg metformin XR to cure my dawn phenomenom. Should I take B12 supplement too? What is the best time to take it? Thanks. Bambang

  13. RJ says:

    I take metformin and my b22 is high at 1400. What should I do to get it down ?

  14. Derrick Sloan says:

    Please people don’t put all of your trust in these death dealers. They call it practice medicine for a reason. And reason is to keep pushing prescription (synthetic drugs) which are foreign to the human body for more money from major pharmaceutical companies. Natural Herbs, Foods, and Exercise is the key to offsetting the condition of diabetes. Last but not least (Diabetes is not a Disease).

    • Ayn Marx says:

      O.K.,but please show at least as much scepticism toward these prescriptions as you do toward main-stream drugs; ‘natural’ products include lobelia, datura, and deadly nightshade,and your body doesn’t understand the labels ‘natural’ and ‘artificial’, it just sees chemicals.

  15. J Noel says:

    Metformin messed up my muscles and nerves. It worked great on my diabetes, my A1C was good, glucose always in normal range, but the unexplained muscle weakness that set in after being on it for awhile was horrid; my doctor thought I had MS. I wasn’t even able to walk a few hundred feet without my leg muscles giving out. So even with normal glucose levels, neuropathy began occurring in my feet and then started in my fingers, which seemed odd. While researching the meds I was currently taking, I found out about the B12 problem and convinced my doctor to take me off of it and put me on another medicine (one that’s apparently now causing lawsuits) and I can once again do most of the things I could before. I can even cut grass with a push mower on an incline without having to stop all the time now, plus the neuropathy stopped progressing in my fingers and I still have some feeling in them, but my feet are screwed. Before discontinuing, I’d be lucky if I could cut a 50′ x 25′ flat yard without having to sit. So if you take it, I’d ask your doctor to check your B12 levels. My doctor didn’t even know about the B12 thing, so there’s a chance yours doesn’t either. (Cross posting.)

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