How does chronic use of metformin impact B12 levels?

Chronic use of metformin has been associated with decreased absorption of vitamin B12. The exact mechanism is thought to involve the alteration of gut motility and changes in the small intestine’s microbiome, which can interfere with the absorption of this essential vitamin. It can also lead to bacterial overgrowth, which could contribute to B12 deficiency.

Vitamin B12 is crucial for nerve function and the production of DNA and red blood cells. As such, individuals on long-term metformin therapy should be monitored for B12 levels to prevent deficiency, which can lead to anemia and neurological issues. This correlation highlights the importance of routine screening for B12 levels in patients taking metformin over an extended period.

In contrast, while the other options suggest increased absorption, no effect, or promotion of intrinsic factor production, they do not align with the established understanding of metformin's impact on vitamin B12 status.