L-Carnitine

Also known as: levocarnitine, carnitine

IM / IV / SQ TherapyWeight Management

In plain English

L-carnitine is a natural compound that helps the body turn fat into energy by shuttling fat into the cell's energy factories. It is an essential, proven treatment for people who are genuinely carnitine-deficient. In wellness and weight programs it is added to "fat-burning" injections and GLP-1 blends, but strong proof that it causes weight loss in people with normal carnitine levels is lacking. It is generally safe; high oral doses can cause GI upset and a fishy body odor.

The science

L-carnitine transports long-chain fatty acids across the inner mitochondrial membrane for beta-oxidation. In primary carnitine deficiency (an SLC22A5/OCTN2 transporter disorder), lifelong oral levocarnitine (100-200 mg/kg/day) is the standard, life-saving therapy that prevents cardiomyopathy, myopathy, and hypoglycemic decompensation, with strong observational support (e.g., 10-year Faroe Islands cohort). Its addition to lipotropic and GLP-1 compounded injections for weight loss in carnitine-replete individuals lacks robust randomized evidence of benefit. Adverse effects include GI upset and trimethylamine-associated body odor; parenteral use for deficiency is FDA-approved, while weight-loss use is off-label.

References

• El-Hattab AW, GeneReviews: Systemic Primary Carnitine Deficiency
• Rasmussen J et al., J Inherit Metab Dis 2023 (10-yr L-carnitine follow-up)