Is B12 useful for blood sugar?

Whether vitamin B12 is useful for blood sugar requires a nuanced answer. B12 is not a direct agent for lowering blood glucose. It plays a key role in energy metabolism and nerve function. Deficiency can cause fatigue and neuropathy, symptoms that overlap with diabetes or insulin resistance. Some observational studies suggest a link between low B12 levels and increased insulin resistance, especially in people taking metformin, which impairs B12 absorption. However, evidence for a direct blood-sugar-lowering effect of B12 is weak and mostly based on mechanistic reasoning and observational data. Robust randomized controlled trials are lacking. Therefore, B12 is not recommended as a primary intervention for blood sugar control, but maintaining adequate levels is important for overall health. If deficiency is suspected (e.g., vegan diet, gastrointestinal issues, metformin use), testing and supplementation are advisable. The evidence level is moderate, as no strong clinical data support a causal role in glycemic improvement.