Vitamin B12 Deficiency and Long-Term Metformin Use

By Leslie Vandever

When it comes to treating type 2 diabetes, metformin is the most widely used and effective drug in the world. It was first approved for use in the U.S. in 1995. Metformin helps keep blood glucose (sugar) levels under control. It makes the liver, muscle, fat and cells more sensitive to the insulin made by your body. It also decreases the amount of glucose you absorb from your food and the amount made by your liver.

Metformin can cause vitamin B12 (cobalamin) deficiency in older patients, patients taking higher doses and patients that have been taking it for a long time.

Metformin and Vitamin B12 deficiency
A vitamin B12 deficiency can be serious. Vitamin B12 is an essential micronutrient that’s needed for DNA synthesis, nerve and brain function and cellular repair. And, without it, your body can’t make red blood cells, which carry oxygen throughout the body. If you’re B12 deficient, you may become anemic.

Metformin can also—very rarely—cause lactic acidosis, which can be fatal.

The average adult needs 2.4 micrograms of vitamin B12 per day and it can’t be made in the body. Instead, it comes from the animal foods you eat, like meat, dairy products, eggs and seafood. Vegetarians and vegans are more likely to become vitamin B12 deficient if they don’t eat grains that have been fortified with B12 or take supplements. People who take proton pump inhibiting medications, like Nexium or Prevacid, or an H2 blocker, like Pepcid or Zantac, may also become vitamin B12 deficient.

As we grow older (over 50) we’re more prone to a vitamin B12 deficiency because of age-related problems with absorption from the gastrointestinal tract.

Symptoms of vitamin B12 deficiency are generally slow to develop, but they intensify over time. They may include:

  • Weakness
  • Fatigue
  • Trouble thinking (cognitive difficulties)
  • Memory loss
  • Anemia
  • Tingling, numbness or strange sensations in the hands, legs or feet (neuropathy)
  • Swollen tongue
  • Paranoia or hallucinations

Some damage, particularly to the nerves, can’t be reversed.

A blood test is the surest way to find out if you’re vitamin B12 deficient. A serious deficiency can be treated with weekly B12 injections and/or supplements. But the best way to be sure you won’t become vitamin B12 deficient is to take a daily multivitamin.

For more information about diabetes, vitamins and other health issues, visit HealthLine.

Leslie Vandever is a professional journalist and freelance writer. Under the pen-name “Wren,” she also writes a blog about living well with rheumatoid arthritis called RheumaBlog. In her spare time, Vandever enjoys cooking, reading and working on the Great American Novel.

Anemia—B12 Deficiency. (2012, Feb. 8) MedlinePlus. U.S. National Library of Medicine. National Institutes of Health. Retrieved on February 20, 2014 from

Kiberige, D. and Mwebaze, R. Vitamin B12 Deficiency Among Patients With Diabetes Mellitus: Is Routine Screening and Supplementation Justified? (2013, May 7) Journal of Diabetes and Metabolic Disorders. Retrieved on February 20, 2014 from

Stehouwer, C.D.A. et al. (2010, Feb. 25) Long Term Treatment With Metformin In Patients With Type 2 Diabetes and Risk of Vitamin B12 Deficiency: Randomized Placebo Controlled Trial. BMJ. Retrieved on February 20, 2014 from

Kin Wah Liu, Lok Kwan Dai, and Woo Jean. Metformin-related Vitamin B12 Deficiency. (2005, Dec. 6) Age and Aging. Oxford Journals. Retrieved on February 20, 2014 from


  1. Bonnie Goodwin says

    My podiatrist stated me on NeuRemedy Plus w/methylcobalamin dietary supplement this week when I was diagnosed with foot neuropathy. It adheres to the fat u digest when you eat (I take it with meals as directed) It’s not a subscription. Its 50.00 for the first mnth supply and 25 after that. My doctor said he has been suggesting it to his diabetic patients and has a over all success rate with helping to manage levels and the neuropathy and you will see a difference as soon as two weeks if it works for you. It helps your B12 levels. I hope it works well for me I don’t enjoy the thought of adding more meds with side effects.

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