Based on our analysis of 21 RCTs, we found that supplementing with L-carnitine can lead to significant improvements in various health markers, such as TG, LDL, FBG, HbA1c, HOMA-IR, CRP, TNF-α, weight, BMI, BFP, and leptin levels in patients with diabetes and glucose intolerance. This evidence concerns the gene TNF and diabetes mellitus.