Metformin Affects Vitamin B12

It’s now well established that Metformin affects levels of vitamin B12. This is an important article for anyone who takes Metformin.

The most common medication used in women with PCOS is the insulin-sensitizer metformin. Research is strongly showing that long-term use of metformin and at high doses (1.5mg or higher daily) can deplete levels of vitamin B12. A deficiency of vitamin B12 can cause permanent neurological and nerve damage as well as mood changes and decreased energy. Here’s what you need to know to avoid a vitamin B12 deficiency if you take metformin.

About Metformin

Metformin is a medication that became available in the U.S. in 1995 for the treatment of type 2 diabetes. Metformin is the most widely used medication used to lower insulin levels in those with polycystic ovary syndrome. Other names for metformin include glucophage, glucophage XR, glumetza, and fortamet.

Metformin lowers blood glucose levels in three ways:

  1. It suppresses the liver’s production of glucose.
  2. It increases the sensitivity of your liver, muscle, fat, and cells to the insulin your body makes.
  3. It slows the absorption of carbohydrates you consume

Metformin use affects the absorption of vitamin B12 possibly through alterations in intestinal mobility, increased bacterial overgrowth, or alterations of the vitamin B12-intrinsic factor complex.  Metformin can cause a malabsorption in B12 due to digestive changes, which leads to the binding of B12-intrinsic factor complex (intrinsic factor is needed to absorb B12 in the gut) and a reduction of B12 absorption.


Vitamin B12 Deficiency in Metformin Users

The largest study thus far to examine the link between metformin and affects on vitamin B12 is the Diabetes Prevention Program Outcomes Study (DDPOS). This study looked at B12 levels of individuals with prediabetes who took 850 mg Metformin 2x/day and compared them to those taking a placebo. At 5 years, 4.3% of the metformin users had low levels of B12 (<203 pg/ml) vs 2.3% of placebo takers and 19% of metformin users had borderline low B12 levels (204 –298 pg/ml) compared with 9.5% of placebo.

Vitamin B12 levels decreased over the years among individuals who took metformin. At 13 years, 7.4% of metformin users had low B12 levels and 20.3% had borderline low levels.

One study published in the Journal of Clinical and Diagnostic Research found that 33% of individuals who took metformin were deficient in Vitamin B12

A 2015 systematic review and meta analysis which looked at a large number of studies, concluded that metformin treatment is significantly associated with an increase in incidence of B12 deficiency and reduced serum VB12 levels.

Nearly a third of adolescents with clinical insulin resistance had a low or borderline serum B12 status in a study published in Nutrients.

The prevalence of vitamin B12 deficiency in metformin-treated type 2 diabetes patients in Korea was 9.5%. Vitamin B12 deficient patients had longer duration of metformin use and higher daily metformin dose.Vitamin B12 deficiency was defined as vitamin B12 ≤ 300 pg/mL without folate deficiency (folate > 4 ng/mL).

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B12 Deficiency Among Metformin Users With PCOS

Studies done investigating metformin use in women with PCOS are severely lacking. There is much more data on people with diabetes who take metformin with the majority of the evidence showing metformin affects vitamin B12 levels. As for studies done in women with PCOS, here is what the evidence shows:

A 2014 Systematic review and meta-analysis looked at individuals with type 2 diabetes and women with PCOS who took metformin. The higher the metformin dose, the more deficient people were in vitamin B12. The effect of metformin on vitamin B12 levels was nearly the same in patients with type 2 diabetes and PCOS. Moreover, metformin reduced vitamin B12 concentration in both long (≥3 years) and short (<3 years) term.

One study in Nutrients found serum B12 levels declined and reached significant lower levels after just six months of treatment in women with PCOS taking 1.5-2.5 grams of metformin daily.

In 2009, Kaya et al. found that vitamin B12 concentrations were significantly lower in obese PCOS women in comparison with obese control women.

Women with PCOS tend to take higher amounts of metformin (average dose is 1,500-2,000 mg daily) than those with diabetes to help manage insulin resistance.  Both long-term use and high dosage intake as seen in the PCOS population, are risk factors for vitamin B12 deficiency.

About Vitamin B12

Vitamin B12 is a water-soluble vitamin that is required for proper red blood cell formation, neurological function, and DNA synthesis. There’s some evidence that vitamin B12 may help prevent heart disease and possibly even Alzheimer disease. This vitamin is found primarily in animal foods, such as beef, seafood, eggs, and dairy products, which is why some vegans are at risk for a B12 deficiency (click here for a list of food sources of B12). Elderly people are often at risk for deficiency as well, due to problems with absorption from the gastrointestinal tract.

Symptoms of B12 deficiency include certain types of anemia, neuropathy (nerve damage), chronic fatigue, memory loss, confusion, mood changes and even dementia. Pernicious anemia, a severe form of long-term vitamin B12 deficiency is an autoimmune disease that affects the stomach. If you experience any of these symptoms, see your doctor immediately.

The PCOS Nutrition Center PCOS MULTI™ contains extra amounts of vitamin B12 and 19 other vitamins and minerals to support health in those with PCOS*

Metformin affects vitamin B12 levels

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Supplementing with Vitamin B12

Individuals who take metformin get B12 levels checked annually. A simple blood test can assess vitamin B12 status. Normal lab reference ranges may vary by lab. Values below approximately 170–250 pg/mL (120–180 picomol/L) for adults indicate a vitamin B12 deficiency. Elevated serum homocysteine and methylmalonic acid levels may also indicate a B12 deficiency.

Authors of the book, Could It Be B12, say levels to indicate a vitamin 12 deficiency are too low and that people with levels under 400 pg/mL could very well be deficient with B12 and have effects.

All individuals age 14 or higher need 2.4 mcg B12 daily whether they take metformin or not. Women who are pregnant or nursing will need slightly more.  Mandatory supplementation with B12 has now been proposed for those taking metformin. Taking a daily multivitamin containing 100% of the daily value (DV) for vitamin B12 may do the trick although many of our patients who take a mulitivitamin with B12 and are on high doses of metformin are still deficient in vitamin B12, requiring extra supplementation.

The best absorbable form of Vitamin B12 is methlycobalimum. Taking vitamin B12 sublingual (under the tongue) is recommended for over the counter B12 supplements.

We recommend all our patients who take metformin, have their vitamin B12 levels checked annually. Many women with PCOS also take oral contraceptives which also may interfere with B12 absorption and should also have B12 levels checked. The amount of B12 to take should be individualized and discussed with your doctor or registered dietitian nutritionist.

Have you had your levels of Vitamin B12 checked? Share with us by leaving a comment below.


Aroda VR, et al. Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab. 2016;doi:10.1210

Ingole JR, Patel RD, Ingole SJ, Pandave HT. Opportunistic Screening of Vitamin B12 Deficiency in IT Professionals Presenting for Routine Health Check-up. J Clin Diagn Res. 2015 Dec;9(12):OC01-OC02.

Niafar M, Hai F, Porhomayon J, Nader ND. The role of metformin on vitamin B12 deficiency: a meta-analysis review. Intern Emerg Med. 2015 Feb;10(1):93-102.

Ho M, Halim JH, Gow ML, El-Haddad N, Marzulli T, Baur LA, Cowell CT, Garnett SP. Vitamin B12 in obese adolescents with clinical features of insulin resistance. Nutrients. 2014 Dec 4;6(12):5611-8. doi: 10.3390/nu6125611.

Ko SH1, Ko SH1, Ahn YB1, Song KH1, Han KD2, Park YM3, Ko SH1, Kim HS1. Association of vitamin B12 deficiency and metformin use in patients with type 2 diabetes. J Korean Med Sci. 2014 Jul;29(7):965-72.

Liu Q1, Li S1, Quan H1, Li J1. Vitamin B12 status in metformin treated patients: systematic review. PLoS One. 2014 Jun 24;9(6):e100379.

Greibe E, Trolle B, Bor MV, Lauszus FF, Nexo E. Metformin lowers serum cobalamin without changing other markers of cobalamin status: a study on women with polycystic ovary syndrome. Nutrients. 2013 Jul 5;5(7):2475-82.

Kaya C, Cengiz SD, Satiroğlu H.Obesity and insulin resistance associated with lower plasma vitamin B12 in PCOS.Reprod Biomed Online. 2009 Nov;19(5):721-6.

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Comments (48)
  • Linda Socher

    May 5, 2011 at 8:05 pm

    Hi- Great web site! Thanks for posting this important piece of information about metformin and vitamin B12 deficiency. It’s crucial for diabetics to be aware of the risks so that they can avoid becoming B12 deficient and developing severe nerve damage. Thanks for allowing my comments.

  • Dorothy Joseph

    May 28, 2011 at 8:04 pm

    I was feeling really run down after started taking Metformin and a Physical Therapist friend of mine said she got B12 shots to give her more energy, so I looked into the B12 deficiency and Metformin. I discovered this correlation when I did my own research back about 12-15 months ago. I shared this connection with my Gyno. She now recommends B12 supplement to all PCOS patients taking Metformin.

  • Jackie

    May 28, 2011 at 8:05 pm

    This is good information to know. My daughter has been on metformin for PCOS for a couple of years now, and no one has ever mentioned the need to check a B12 level. Lately she feels her hair is falling out excessively/more than normal and that it’s noticably thinner. She also takes spironolactone and birth control pills. She recently read that women with PCOS may be more prone to zinc deficiency. Is there any evidence for zinc deficiency with PCOS? Thank you.

  • Gail

    June 1, 2011 at 8:05 pm

    If the deficiency is the result of changes to intrinsic factor then a multi with B12 in it is unlikely to be helpful. Intrinsic Factor is responsible for the absorption of B12 in the gut, if it’s not working you can’t absorb B12 from oral doses. You would need either an injection or the sublingual/chewable version of B12. Also 2.4mcg will be the RDA for B12, enough to prevent outright deficiency symptoms in otherwise healthy people, but probably not enough in these sort of circumstances.

  • Adele Downer

    December 28, 2011 at 8:05 pm

    I have been seeing an FNP for approximately 3-years for PCOS and I am being treated with 1500mg/day of Glucophage. I recognized mental acuity changes, difficulty concentrating,etc. and researched Glucophage and found it impairs B12 absorption so I asked that a B12 level be drawn. I called for my results a week later to find that my level was 285 and on the low end of the reference range of 211-946. The FNP had made a note in my chart that it was “okay to begin supplementation with OTC B12.”

  • Renae

    March 9, 2012 at 8:06 pm

    Hi, I have been doing a bit of research on this as well. There is now a vitamin B12 patch that can be used instead of injections, and there is no need to worry about absorption issues.

  • Nancy

    April 3, 2012 at 8:06 pm

    I’ve been taking metformin for 10 years for diabetes. I had been complaining loudly and persistently for 2 years or more to my family physician as well as my endocrinologist. FINALLY, 2 months ago, my GP tested B12 levels and it was found to be 114. Now wonder I’ve been struggling. Am taking 1000mcg per day in addition to a once a month injection of 1000mcg. Not sure if the metformin is blocking absorption of the daily B12. Feeling better but now great. I am planning on a serious talk with the endo next week about getting off metformin. Enough is enough.

  • Mindy

    April 20, 2012 at 8:06 pm

    I just started taking Metformin about a month or so ago and within the last couple of weeks I have been feeling extremely exhausted and my hair HAS been falling out. I thought my thyroid was out of whack again but after testing and coming back normal, I am left wondering what is going on. I am going to ask my Endo about the B12 levels. I do take a daily multi-vitamin but not sure if that is enough in this case. Will a vitamin supplement such as Super B Complex (15mcg of B12)be useful in attaining proper levels or does it have to come in the form of an injection or patch? I have PCOS, IR, and Hypthyroid/Goiter. Thank you.

  • jeanette

    March 15, 2013 at 8:06 pm

    some years ago after tests I was told I needed to have b12 injections also that my consultant recomended that I stop taking metformin which I had been taking for a couple of years.( I have type 2 diabetis ) this was some years ago, about 3 years ago I saw a different Consultant who prescribed me Byetta and again metformin when I questioned him about this he said that any trouble I had in the past would not now be a problem as the drug had been refined. I hate the b12 inections but I have been told I will have to take them for the rest of my life, can I not be tested to see whether I still have the problem or will it be unsafe for me to stop taking the injections to find if I am in need of b12 injections.

  • Pamela

    August 12, 2013 at 8:07 pm

    This makes perfect sense! I started taking metformin regularly in late April or early May, I forget. I was taking a multivitamin until mid June, when I ran out and forgot to buy new ones. After a week or so, I found I had no energy at all. I wasn’t sure what was the source of my lethargy, thought maybe allergies or something… then as it persisted, I thought what has changed? and I remembered that I’d stopped taking vitamins. I started taking them again and bam, I’m normal. I knew there had to be a deficiency, but I wasn’t sure what. I know PCOS is supposed to have connections with magnesium and vitamin D, and maybe they play a part too, but I’m guessing it is the B-12 in that B vitamins have such a link to energy.

  • Bev

    August 28, 2013 at 8:07 pm

    I have been taking Metformin from 1999 onward, almost all of my hair has fallen out. I have been sent to a doctor who found no reason. In the last 22 weeks I have been on a medication for a medical condition, that leaves me tied and I have been reallizing I have been this way for years. I am retired and if I can get the dishes once a day I am feeling good. I will see my Dr of 35 years tomorrow and ask for b12 shots and lots of daily. I have been drinking 600% of daily intake in a sugar free energy drink and have felt almost human for the last 2 weeks. I was never warned of b12 loss but I also understand it may be causing the hair loss. Many people have spoke of Metformin = hair loss due to b12 deficiency. Wish I had known this 10 years ago. Thanks for your article.

  • Angela Grassi

    August 28, 2013 at 8:07 pm

    Bev, let us know what happens.Be sure to ask for a B12 test. Blood levels of B12 should be 400 or greater.

  • Marlene

    September 2, 2013 at 8:08 pm

    I have been experiencing extreme tiredness for quite a number of years. I have been through some personal turmoil the past 3 years and thought that stress was a contributing factor to my even more declining energy levels. It was not until April 2013 when I as diagnosed with Pernicious Anemia, but was later told that I did not have it. I started getting an extreme heavy feeling in my legs until I was barely able to move and have had very painful stitches in my feet and lower legs. Headaches was a consistent part of my life. Therefore the trip to the doctor and the eventual diagnosis of PA. I did not find the GPs very helpful. None of them ever warned me about taking Metformin for PCOS. I have taken 850mg three times a day with Noriday and Aldactone. In the two months that I was barely able to walk, I started reading up on B12 deficiency. Needless to say that the doctor was very reluctant to prescribe B12 and reluctant for me to have the injections. She nevertheless prescribed it and I have been injected with it since April. I was able to walk again at the end of May but in the process have learned that it might be best to get Beriglobin injections as I also have suffered from flu-like symptoms for many years, such as sore throat, rhinitis, ear infections and low-grade fevers. A light bulb went on as I have had these injections years ago and remember how it boosted my energy. I was unable to get it into my country of residence and have gone to South Africa to get a series of injections. Other countries where it is freely available is Germany and Austria. It is also available online but with a doctor’s preion and check if you can get it past customs. If anyone wants to read more about B12 deficiency, check out which is a wonderful site/support group. I also want to mention that a B12 deficiency also influence the iron levels. I am taking 2 Ferro-Tabs (200mg each) once a day with 500mg Vitamin C for better absorbtion. The GP who initially diagnosed me with PA did not help me at all regarding the iron, but only prescribed the tablets. I had to find out for myself that it would be better absorbed if taken with vitamin C. I have heard from the drug store that pineapple is very rich in Vitamin C and will help. I am also taking Magnesium Complex Plus, Fish Oil, Zinc, Selenium and a B-complex. Do know that B12 is only effective when injected. I have learned that too from reading up and by confirming it with the doctor who is now injecting me with Beriglobin and I also getting B12 in addition to boost my immune system. B12 tablets or patches are not effective. I, of my own accord, started taking Metformin 2x a day, instead of 3x per day. I don’t know if anyone have been through the same/similar symptoms but I can assure that I already feel better after getting the Beriglobin. I am not saying that this is the ultimate cure but it was worth a shot after having to go through all of the above mentioned. I hope some of the information might be useful to someone.

  • Michele

    October 7, 2013 at 8:09 pm

    I was on metformin for PCOS – i voluntarily took myself off it about 14 months ago, and 2 months ago my b12 was 127ml, iron def, and vit D deficient. Things weren’t feeling right which is why i dropped of the met and changed my birth control method. just thought i’d chime in if anyone keeps up with this still.

  • Jen

    March 13, 2014 at 8:10 pm

    Not sure if anybody reads this far in the comments but I wanted to note that if at all possible people should be taking methylated b-12– this is critical. Many people have genetic mutations that cause their bodies to have a hard time processing standard b-12 into methylcobalamin (active/methylated b-12) and it makes sense that the people feeling b12 deficient easiest are the ones who most need the active form. It is dangerous to have too much standard B12 roaming around your body if you have a MTRR mutation.

    Also, be aware of signs of too much B12, which I think are primarily restlessness and anxiety, and adjust your dose as necessary.

  • Ashley

    June 1, 2014 at 8:10 pm

    Wow! Now I understand why im so tired, every day and in the morning i feel like a robot my legs feel so stiff my OB had made test on diabetes, thyroid and blood levels and he tells me that everything is ok, yes i have been having problems concentrating, in other words taking B 12 vitamins pills will not be absorb ?? Only if you get the injection??

  • Angela Grassi

    June 1, 2014 at 8:10 pm

    Ashley, you should have your B12 levels checked. While a B12 injection is best absorbed, you may be fine supplementing with methlyated oral sublingual B12 (under the tongue). B12 injections are usually reserved for those with significantly low B12 levels. Let us know what you find out!

  • Jean Strachan

    June 2, 2014 at 8:11 pm

    I was on Metformin for a number of years. I was having trouble with my gut. One to two hours after having a bowel moment I would unknowingly leak out faeces. It got so bad

    that I had to use sanitary towels. I was checked out by a gastroenterologist but nothing untoward was found. I also was extremely anaemic. I was put on iron pills and then iron injections and finally a intravenous drip every few days. I was also vitamin B12 deficient. I decided to do some research on the Internet and bingo! Metformin was the cause. I went off it for a few days and the leaking faeces stopped. The dr said it was just coincidence so I took metformin for a few days again and was back to square one. I’m on a different medication at my insistence and I am a different person. I think drs should be made aware of this as I went through a tough time. This shouldn’t happen to anyone. Keep well, Jean (68)

  • Amy

    July 23, 2014 at 8:11 pm

    I have been on metformin 500mg twice a day.I have been on it for about 5 years now. I am the same as soon as I eat maybe 30 min. later running to the bathroom. I have bowel leakage sometimes at night but not all the time. I keep telling my Doctor that I am very tired all the time. It takes everything out of me just to do my daily chores. I am going to ask for a B 12 blood test when I go in to see the Doctor. I was never so tired in my life. This has been going on for so many years. I would love to be outdoors fishing,swimming and playing with my children. I now feel like it is a big struggle just to do this. Thanks for the info!

  • Rhonda

    March 3, 2015 at 8:12 pm

    I wish I’d read this article a month ago. I have PCOS and metabolic syndrome..reactive hypoglycemia, insulin resistance, etc. My endocrinologist prescribed 1500mg of metformin daily. One 500mg tablet in the morning, 2-500mg tablets in the evening. I began experiencing horrible neck pain, headaches, and tingling in my well as the worst persistent nausea I’ve ever known. I was convinced it was my medications (I was prescribed metformin as well as other drugs for treatment for my conditions). I’d be so nauseated..for neck hurt. My head pounded. My fingers tingled..The nausea was bad enough that I’d stop taking the medicine. My neck stopped hurting. The headache went fingers stopped tingling. I felt better, so I’d start taking the medicine again. An xray and two MRI’s later..there’s NOTHING on the film!! There’s nothing structurally disk problem, no tumors or any other growths..NOTHING. I was glad, but also nearly in tears of frustration..I still had zero answers. I had blood drawn at one of my visits with my endocrinologist..I was vitamin D deficient. I didn’t know enough to ask about any other vitamin levels. I was prescribed a once-weekly supplement, the level was corrected and that was that. I’m going to get a second opinion from a different endocrinologist at a different office..that appointment is roughly 2 weeks away. Then I see this article.. WOW. I’m not sure if my B12 levels are/were low, but I do know that I was taking metformin and suffered neurological problems at the same time. My last dose of metformin was 2/10/15. I haven’t had a headache, no neck pain and ZERO nausea since then. Thank you for this article. I’m taking a copy with me to the new endocrinologist when I go.

  • Bea

    March 4, 2015 at 8:12 pm

    I’ve been on Metformin since 2004, and taken B12 supplements since about 2008 on and off (whenever it got low), this year doc decided I’m taking it permanently.

  • Sara

    March 20, 2015 at 8:12 pm

    I have been taking Metformin 1,500 mg in conjuction with Lo Lo Estrin to treat PCOS for alomost two years. I actually went off them for several months because when taking the medication I would start to feel tired and achy and alomst flu like. I felt better after I went off but of course I needed to go back on. After about 3 weeks back on the medication I started to feel overly tired and sluggish again. My Dr. Still thinks its all in my head…which shocks the hell out of me because up until now she has always been a great Dr., I am currently looking for another GYN to get a second opinion but I was so relieved when I saw this aritcle. I started taking a b12 supplement and I must say that after only a few days I feel better then I have in months.

  • Mary R. Rinaldi

    May 17, 2015 at 8:13 pm

    An exceptional article! Thanks the writer. I’ve been a diabetic patient for 5 years, and have been taking Metformin So that I could keep my blood sugar under control. I’m now 59. I started going through anemia, weakness, and mood disorder from the beginning of the last year. I met an experienced doctor and was diagnosed with Vitamin B12 deficiency. My doctor confidently advised me to consume Vitamin B12 supplements. For being not interested in animal foods (As you mentioned) and taking Metformin for many years, I was at high risk of Vitamin B12 deficiency- my doctor said. However, I feel pretty well now.

  • Marlene

    September 28, 2015 at 8:13 pm

    I have used Metformin and there is another side effect that has not been mentioned. Metformin can cause Memory Loss. I have been having this trouble after using it. My doctor did not tell me of this side effect till after it was a symptom that I was having. I live alone and now really need someone to stay with me. What I want to know is why this drug is on the Market and why aren’t patients told of this side effect?

  • Anna

    October 26, 2015 at 8:14 pm

    Wow. Great info. Glad I found it. I had an issue swallowing that didn’t stop til I had some vitamins..especially the electrolyte vitamins..magnesium..etc… and now will be adding more b12 to diet. I realized I was lacking vit adding that to avoid the muscle or swallowing issue. I wonder if any others had same experience or effects of the meds… well this caught my eye and I’m grateful for such info…wondering why Dr doesn’t share such with us

  • James

    October 28, 2015 at 8:13 pm

    What about slurred speech caused by taking metformine for a number of years which has caused nerve damage by lack of vitermin B12

  • Eve

    October 28, 2015 at 8:14 pm

    oh!i am so glad i came across your site -i thought i was dying falling asleep at about 4.30pm and not waking till 14 hrs later or sleepimg for 2 hrs at a time ! my hair is falling out im dreading coming it and i just had morbid thoughts that i was dying —ive cut the glucophage down to 2 500mg er in the morning as so far have stayed awake but horrendous sleeping pattern frightens me im 78yrs old the dr told me to take 4 tabs of 500 but i cant —my hair is so thin i will deff get vitamin b12 tomorrow —great site!

  • carrie

    November 28, 2015 at 8:15 pm

    I have been on Metformin ER for 11 months now as well as Othrotycyclen Lo (birth control) and have been on a recommended b vitamin for 3 months. I’m having to switch vitamins because I’ve been having extreme dizziness from niacin flush.. I’m only taking 100mcg right now but feel no difference so I’m going to up the dosage to the recommended 1000 a day for metformin users. Ever since I began Metformin, my hair has been continually falling out, like every time I wash my hair or brush it wads fall out. I have severe thinning at the back of my head, migraines, vertigo, memory loss, mood swings.. the works.. I have PCOS and am only 24 years old. I always feel so weak and tired and am starting school soon and I’m thinking about quitting metformin if all of this doesn’t improve with the higher dose of b12.. I wish you all the best and thanks for reading 🙂

  • Sherry

    August 12, 2016 at 11:26 pm

    Well I’m right there with the rest of you but did not know it was the metformin that is causing it all …im so tired as much when I wake up as before I sleep memory problems, losing hair by the hand full dry mouth and eyes. Vit B12 and vit D both extremely low having to take supplements of both.only found out they were low when I ask my doctor to check because of the hair loss and still nothing was said about the metformin.!!

  • Kim

    August 16, 2016 at 12:42 pm

    My diabetic nurse tells me nothing been on metformin since dec 2015 and take vit b12 as had bels pawlsy after car crash in octobet but was unaware of this and slso on avortastatin as aprently has to be under five if you diabetic mine was 5.4 all theses drugs prob killing my brain cells

  • Tracey

    September 16, 2016 at 9:37 am

    Was diagnosed back in 2008 with pcos, have been on metformin,spironactone and the pill since then. Back in 2014 I began feeling larthargic to which my annual bloods came back with my b12 at 147 to which my consultant told me to take B12 supplements. As we went into a new year (2015) I became worse, blurred vision which I now wear glasses. The tiredness was so servere I don’t know how I Managed to get out of bed. What with work (cleaner) 4 children and a dog I really struggled to cope. When I went for my annual check up in 2015 by b12 bloods came back at 99. This indeed explained why I had felt so rough. I went straight onto monthly injections and now on 3 monthly and am really in a different place even though it’s taken a while. Having an annual check up next month and hoping that no has gone up. I had other side effects the mental fog as they call it and pins and needles in my hands and feet were bad to.
    If you take metformin and you feel extra tired get them to check your b12 straight away I would hate for anyone to be in the position I was when it was low for a long time.

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  • Jacqueline mckenzie

    October 21, 2016 at 7:44 am

    In my opinion it is a case of chicken and egg here only we can’t see what is chicken or egg. is it not possible that these people with PCOS and insulin problems have a b12and cofactors deficiencies that actually cause these problems and not the other way around.
    National blood testing regulator has warned for a number of years that b12 tests are inaccurate and doctors should look at symptoms. A new test which measures active b12 is becoming more widely available. The levels we use to class a deficiency is too low. Symptoms although vague and multiple are evident with b12 level over 500 . In Japan a person is deficient at a level of 500,,,, think about it…. The people in the tests my already be deficient but it is not showing on the tests. Basically I think we should be communicating with Japanese specialists and sharing knowledge and feel the this research is probably skewed because of the very low levels defining a deficiency and also the skewed unreliable b12 tests being carried out.

  • J Noel

    February 16, 2017 at 5:05 am

    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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  • lynda

    November 12, 2017 at 6:15 pm

    My GP recently told me I don’t need to have B12 checked annually as deficiency only affect those diagnosed with Diabetes not when diagnosed with PCOS and other hormone issues. There is no joined up thinking among GPs

  • Angela Grassi

    November 13, 2017 at 9:16 am

    That information is false. If you take metformin, you need to have your Vitamin B12 levels checked annually and supplement your diet. You do not want to mess with low B12 as it can cause serious and permanent changes to your health. Maybe it’s time for a new doctor???

  • Jackie

    July 10, 2018 at 4:12 pm

    Can you suggest a good B12 supplement? The supplement market is overwhelming with so many choices, none of them regulated.

  • Angela Grassi

    July 15, 2018 at 3:21 pm

    We will have a supplement with B12 soon in our supplements store. Stay tuned!

  • Lola Rebekah Chadwick

    August 4, 2018 at 1:48 pm

    What is the best b-12 medicine to take while taking metformin 500 mg

  • Angela Grassi

    August 7, 2018 at 3:50 pm


  • Jennifer

    September 16, 2018 at 12:10 am

    I had my B12 level checked and they said they were way to low, i would have to look again. I have pcos but don’t have a doctor right now cause I don’t have insurance neither. What should I do

  • Angela Grassi

    September 18, 2018 at 5:05 pm

    You could start taking a B12 supplement and see if you feel better. Low Vitamin B12 levels are dangerous!

  • Fannie Sistrunk

    November 13, 2018 at 5:57 pm

    If I’m taking metformin twice a day will B 12 be good to take

  • Angela Grassi

    November 19, 2018 at 8:59 am

    I would recommend a minimum of 250 mcg daily but good idea to have your levels tested to see if you need more than that.

  • Elmer Richards

    January 7, 2021 at 9:29 am

    I have been on 1000mg of metformin twice a day for several years and have had severe leg and foot pain. I recently red a posting on line entitled “metformin kills legs”. It told of metformin robing the body of vitamin B12 and that prompted me to try discontinue taking metformin and taking vitamin B12. I have been doing this for about three weeks and have had much less leg pain and better movement in my right knee in which I have had a lot of arthritic pain. I will be seeing my doctor on Jan. 20th and will discuss this with her.

  • Angela Grassi

    January 15, 2021 at 2:05 pm

    Good to hear!

  • Santa

    September 12, 2022 at 5:43 am

    Thank you for sharing such a knowledgeable blogs, after reading your blog i have understood many things related to vitamin B12 and metformin.

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