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Metformin Led to Vitamin B12 Loss and Excruciating Pain

A first-line diabetes drug can lead to vitamin B12 loss, with peripheral neuropathy as an extremely painful symptom; ask your doctor to monitor your levels.

Metformin is a first-line treatment for type 2 diabetes, along with regular activity and a healthful diet low in processed foods. While metformin can be extremely helpful in controlling blood sugar and reducing the likelihood of complications due to diabetes, it does have certain side effects. Digestive distress, including nausea, diarrhea, loss of appetite or bloating are among the most common, but they usually disappear after a person has been taking the drug for a while. Some side effects aren’t obvious right away, however. Vitamin B12 loss in particular could sneak up on a person, as some readers have experienced.

Symptoms Suggest Problems with Vitamin B12:

Q. I have taken metformin for years to control my blood sugar. Lately I have been experiencing exhaustion and prickling in my feet. I also lose my patience too easily and have no appetite. Searching online suggests I might have a vitamin B12 deficiency. Should I start taking vitamin B12 supplements?

A. People taking metformin are susceptible to vitamin B12 loss (Cureus, Oct. 2023). However, before starting supplements, it would be better to get tested first. Your doctor could order a vitamin B12 test, or you could order one yourself online. A number of medications, including metformin, can deplete the body’s store of vitamin B12.

Was Crippling Foot Pain a Result of Vitamin B12 Loss?

Q. I have been on metformin since I was diagnosed with diabetes several years ago. About a year ago, I develop debilitating neuropathy. Just going to the store for an hour kept me off my feet for a few days.

My podiatrist suggested a vitamin B complex. After taking it for two weeks, the difference is amazing. My feet hardly hurt at all and I can bend my toes more than I could before. I think I’m getting a little feeling back in areas that are numb.

Vitamin Depletion due to Metformin:

I read on your site that metformin can deplete B vitamins. I have suffered terribly for a year because doctors prescribe medicines without really knowing the side effects. Now I’m going to talk to my doctor about the gas and bloating I get from metformin.

Watching Out for Vitamin B12 Loss While Taking Metformin:

A. Metformin is well known to deplete vitamin B12. Levels should be monitored regularly for those on metformin or acid-suppressing drugs, which also can reduce vitamin B12 absorption.

Symptoms of vitamin B12 deficiency include numbness, tingling, nerve pain, difficulty walking, fatigue and anemia. We are sending you our Guide to Managing Diabetes with more information on metformin and nondrug ways to help control blood sugar.

A Walking Pharmacy Calls for a Vitamin B12 Supplement:

Q. As a 72-year-old with type 2 diabetes, I’m a walking pharmacy. I take three pills for diabetes, one for high blood pressure, two for cholesterol and another for GERD.

One of my diabetes meds is Actoplus MET, which contains metformin. I read in your column that metformin users should consider taking a B-vitamin supplement. What should I look for?

A. If you are taking a PPI acid-suppressing drug like esomeprazole (Nexium), lansoprazole (Prevacid) or omeprazole (Prilosec) in addition to metformin, you probably need a vitamin B12 supplement. Both drugs deplete the body of this vital nutrient.

What Supplements Do You Need to Reverse the Consequences of Your Medicines?

In her book, Fortify Your Life, Tieraona Low Dog, MD, recommends 500 micrograms of vitamin B12 supplement daily for people who are taking either metformin or a PPI. She also suggests alpha-lipoic acid, a multivitamin and vitamin C as well as 300 to 400 mg of magnesium.

To learn more about dietary recommendations, nondrug approaches to controlling blood sugar and a discussion of the pros and cons of diabetes drugs, you may wish to read our Guide to Managing Diabetes. You could also learn much more about the nutritional consequences of drugs and the supplements that might be especially helpful for you by listening to our one-hour interview with Dr. Low Dog. It is Show 1022: How to Pick Dietary Supplements That Make Sense for You.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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  • Tiwari A et al, "Metformin-induced vitamin B12 deficiency in patients with type-2 diabetes mellitus." Cureus, Oct. 2023. DOI: 10.7759/cureus.47771
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