GDF15 and diabetes mellitus: Our analysis showed no causal relationship between GDF-15 and diabetes or fasting blood glucose levels because GDF-15 is a use and dosage biomarker for metformin, the relationship between metformin and GDF-15 was not weakened after adjusting for glycated hemoglobin and blood glucose, and it was independent of insulin and proinsulin, these findings suggest that GDF-15 may be a marker of the non-glycemic effects of metformin.[3,26]