Across 4 studies, all 4 reported beneficial effects on reducing HOMA-IR, with predominantly small effect sizes. The evidence is strongest for adults with overweight or obesity, with one meta-analysis indicating that doses of ≥2 g/day are effective. Study durations were not consistently reported across the literature.
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed).
significant effects of L-carnitine on ... HOMA-IR (MD = -0.58, 95% CI: -0.77 to -0.38)
L-carnitine emerged as the most effective and consistent intervention, producing significant reductions in body weight, body mass index (BMI), waist circumference, fasting blood glucose, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), and LDL-Cholesterol (LDL-C), along with a significant increase in HDL-Cholesterol (HDL-C).
Carnitine supplementation significantly reduced ... HOMA-IR (WMD -0.69, 95% CI -1.26 to -0.13)
L-carnitine supplementation had a significant effect on ... homeostasis model assessment-estimate insulin resistance (HOMA-IR) [WMD = -0.73; 95% CI, -1.21 to -0.25; p = 0.003]