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Evidence-Based Supplement Research
Evidence-Based Supplement Research
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L-Carnitine and Reduced Fasting Blood Glucose Levels

Research synthesisHigh evidenceSmall effect5 studies · 5 beneficial · 0 neutral · 0 harmful

Across all 5 studies in the database, L-carnitine supplementation consistently shows a beneficial effect on reducing fasting blood glucose levels, with all 5 studies reporting statistically significant reductions. Effect sizes are predominantly small (4 small, 1 moderate). The most commonly studied dose is ≥2000 mg/day, and effects have been observed in clinical populations including adults with PCOS and adults with overweight/obesity or impaired glucose tolerance. Median study duration is 42 days (based on one RCT), suggesting effects can appear within 6 weeks.

  • Effective dose range: ≥2000 mg/day
  • Studied populations: adults with PCOS, adults with overweight/obesity, adults with impaired glucose tolerance or diabetes

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). Most trials were of short duration (median 42 days), so long-term effects remain unclear. Several studies are meta-analyses that may share overlapping individual trials, potentially inflating the consistency of findings.

Generated Jun 12, 2026
Doses used in studies
  • L-Carnitine · mg/day: 3,000 (median 3,000, IQR 3,000–3,000) — 1 study
  • g/day: 2 (median 2, IQR 2–2) — 1 study
Time to effect
Median: 6 weeks · IQR 6 weeks–6 weeks · Range 6 weeks–6 weeks — Reported in 1 of 5 studies
5 of 5 papers
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