How are B12 and Blutzucker related?

Vitamin B12 and blood sugar are linked through several pathways. B12 deficiency is common in diabetics, especially those on metformin, which impairs B12 absorption. B12 deficiency can cause fatigue, neuropathy, and cognitive issues that mimic poor glycemic control. Some observational studies suggest low B12 may worsen glucose tolerance and increase insulin resistance risk, but evidence is inconsistent. Conversely, uncontrolled blood sugar may affect kidney function and B12 excretion. The relationship is clinically relevant but multifactorial and not strictly causal. Testing B12 is advisable in diabetes, vegan diets, or gastrointestinal conditions, but it does not replace blood sugar monitoring. Evidence is based mainly on observational studies and clinical practice, not large RCTs. Caveat: individual decisions should be guided by a physician.