Metformin is one of the most common drugs prescribed to help manage type 2 diabetes. It acts to decrease absorption of glucose from the digestive tract, to reduce the amount of glucose produced by the liver, and to increase insulin sensitivity in tissues throughout the body. While it is generally well-tolerated and most users don’t experience any troublesome side effects, it has long been known that metformin can lead to very low vitamin B12 levels. Although the exact mechanism is unknown, it is thought that metformin inhibits absorption of vitamin B12 from the digestive tract.

What is Vitamin B12?

Vitamin B12 is a very important vitamin. It cannot be synthesized by the body, so it needs to be consumed on a regular basis in the diet. It is essential for the production of red blood cells, the synthesis of DNA, and the proper functioning of the nervous system. Individuals deficient in B12 develop problems with the myelin that wraps around the nerves and insulates them. If there is a problem with myelin, conditions like peripheral neuropathy can develop. In severe cases of a B12 deficiency, cognitive impairment and even overt dementia can manifest. Initial symptoms of a deficiency include fatigue, pale skin, numbness or tingling sensations, and difficulty walking or using the hands.

What Food Sources Provide Vitamin B12?

Vitamin B12 is readily available from foods that come from animal sources. Most people are not at risk of developing a vitamin B12 deficiency unless they follow a strict vegan diet, have some kind of malabsorption syndrome, or chronically take certain medications, like metformin or some proton pump/H2 blocking medications used to treat heartburn.

How to Reduce Your Risk While Taking Metformin

Since metformin seems to inhibit but not completely block the absorption of vitamin B12 from the digestive tract, one approach is to adjust the diet to include a lot of animal-based foods. Taking proton pump/H2 blocking medications to treat heartburn should be avoided if possible because reducing the amount of acid the stomach produces makes it difficult for the digestive tract to release vitamin B12 from food in order to allow it to be absorbed.

Learn More

In 2018, the American Association of Clinical Endocrinologists and the American College of Endocrinology released a guideline encouraging clinicians to institute routine testing of patients taking metformin for vitamin B12 levels and adding a supplement (either oral or by injection) to anyone testing low. Although most of the symptoms of a deficiency can be rapidly reversed with injections, once peripheral neuropathy develops, it may become permanent even after correction of the vitamin deficiency.

You can learn more by reading this helpful article Endocrinology Advisor article. If you are currently taking metformin, consider making an appointment at Quench Wellness to discuss your diet, medication, and testing regimen in order to reduce your risk of developing a vitamin B12 deficiency. Contact us today to book your consultation at our office in Chicago.