How does Metformin affect Vitamin B-12 levels?

It is commonly believed that Metformin can cause a reduction in Vitamin B12 levels, possibly by interfering with its absorption or through another mechanism. For this reason, we advise patients on Metformin to either monitor their B12 levels or take extra B12 as a precaution. However, some studies suggest there is no significant connection between Metformin use and B12 levels.

Regardless of Metformin use, it's important to maintain proper levels of Vitamin B12. For adults under 65, the easiest way to get B12 is to take at least one 2,000 mcg supplement each week or a daily dose of 50 mcg. Note that these doses are specific to cyanocobalamin, the preferred supplemental form of Vitamin B12.

As we age, our ability to absorb Vitamin B12 may decline. For those over 65, especially those on plant-based diets, supplementation should probably be increased to 1,000 mcg of cyanocobalamin daily.

B12 supplements are very cheap. Here is one option we found: 5c per 2500mcg tablet, so 5-15cents of cost per week depending on your age.