Amino acid derivative; cofactor for long-chain fatty acid transport into mitochondria
ATC code: A16AA01 (Levocarnitine)
Brand names
Carnitor, Levocarnitine
Endogenous compound synthesised in liver and kidney from lysine and methionine with vitamin C, B6, niacin and iron as cofactors. Binds long-chain fatty acids as acylcarnitine and transports them across the inner mitochondrial membrane via the CPT1/CPT2 system for beta-oxidation. Healthy adults have no deficit: 75% of carnitine comes from diet (red meat, dairy), 25% is synthesised. Oral bioavailability is 14–18% due to presystemic metabolism by gut microbiota to trimethylamine (TMAO precursor).
First line
Levocarnitine is the first-line drug for primary systemic carnitine deficiency (OCTN2 transporter genetic defect) and secondary deficiency on long-term haemodialysis, valproate or pivampicillin therapy, and in preterm infants. The approved Carnitor for this indication in 1985. AEMPS includes levocarnitine in the standard for metabolic disorders of fatty-acid oxidation.
Individual decision
L-carnitine has been studied as an adjunct in chronic heart failure for its role in myocardial energetics. The 2023 guidelines do not mention L-carnitine for heart failure treatment: first-line therapy includes RAAS inhibitors, beta-blockers, mineralocorticoid receptor antagonists and SGLT2 inhibitors. Some RCTs report a small ejection-fraction improvement in dilated cardiomyopathy, but sample sizes are small and independent confirmation is lacking. Use is an individual decision, never as a replacement for evidence-based therapy.
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
L-carnitine is marketed as an endurance and recovery supplement. In 2011 rejected several proposed claims: «improved fat utilisation as fuel», «increased endurance», «reduced recovery time». The ISSN 2018 position stand does not list L-carnitine among ergogenic aids with convincing evidence. Some studies with L-carnitine tartrate report lower muscle damage markers, but the effect size is small and clinically meaningful performance benefit has not been shown.
Not recommended
L-carnitine is marketed for chronic fatigue based on its role in energy production. Healthy adults on a normal diet have normal carnitine levels and do not gain energy from supplementation. NIH ODS states directly: convincing evidence of benefit in chronic fatigue or fibromyalgia is lacking. Persistent fatigue requires workup (ferritin, B12, TSH, depression and sleep screening), not a supplement.
Not recommended
L-carnitine, an amino acid derivative, is marketed as a fat burner promising weight loss through accelerated fatty acid oxidation. The advertising relies on its biochemical role in mitochondrial fat transport. Healthy adults do not have carnitine deficiency, and supplementation does not raise fat oxidation rates. A meta-analysis of RCTs (Pooyandjoo 2016, 9 studies, 911 participants) showed a minimal weight difference vs placebo with wide confidence intervals. In 2011 rejected the «L-carnitine contributes to weight loss» health claim for insufficient evidence. If this product was suggested for weight loss, discuss alternatives with a clinician.
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FDA Category B. Carnitor for primary carnitine deficiency is used in pregnancy without an increased fetal risk. In healthy pregnant women, prescribing L-carnitine «for energy» has no indication and is not recommended by AEMPS or EMA.
Compatible. Hale L2. L-carnitine is endogenous and a physiological component of breast milk. No adverse effects in the infant. Therapeutic maternal dosing (replacement therapy) requires no additional infant monitoring.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Levocarnitine (L-carnitine) is evaluated for the following indications with varying evidence strength: Carnitine deficiency (evidence tier A), Heart failure (adjunctive therapy) (evidence tier C), Weight loss (evidence tier D). See the full indication matrix with dosing and citations above on this page.
Common side effects of Levocarnitine (L-carnitine) (≥ 1 in 100): Nausea and vomiting, Diarrhoea, Abdominal cramps, Fishy body and urine odour (microbiota conversion to trimethylamine). See the Safety section for uncommon and serious reactions.
FDA category B. FDA Category B. Carnitor for primary carnitine deficiency is used in pregnancy without an increased fetal risk. In healthy pregnant women, prescribing L-carnitine «for energy» has no indication and is not recommended by AEMPS or EMA.
Compatible. Hale L2. L-carnitine is endogenous and a physiological component of breast milk. No adverse effects in the infant. Therapeutic maternal dosing (replacement therapy) requires no additional infant monitoring.
Levocarnitine (L-carnitine) is contraindicated in: Hypersensitivity to levocarnitine; Age under 1 month (no safety data in neonates outside specialised protocols). Full list in the Safety section.