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Evidence-Based Supplement Research
Evidence-Based Supplement Research
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L-Carnitine and Reduced Hemoglobin A1c

Research synthesisModerate evidenceMixed effect size4 studies · 4 beneficial · 0 neutral · 0 harmful

All 4 studies reported beneficial effects of L-carnitine supplementation on reducing hemoglobin A1c, with effect sizes ranging from small to large. The most-studied dose range was 1-2 g/day, and effects were observed in adults with type 2 diabetes. One study with a median duration of 253 days suggests long-term supplementation may be needed for maximal effect, but duration data were limited.

  • Effective dose range: 1-2 g/day
  • Studied populations: Adults with type 2 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). Effect sizes varied considerably across studies (small to large), with the highest-quality meta-analysis reporting a small effect (-0.16% HbA1c reduction). Only one study reported treatment duration, limiting generalizability of timing. No specific form of L-carnitine was consistently reported.

Generated Jul 15, 2026
Doses used in studies
  • g/day: 1–2 (median 1.5, IQR 1.25–1.75) — 2 studies
Time to effect
Median: 8.4 months · IQR 8.4 months–8.4 months · Range 8.4 months–8.4 months — Reported in 1 of 4 studies
4 of 4 papers
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