L-carnitine Base type, special purity > 99% It is a naturally occurring amino acid.
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Benefit
Typical study dose*
Key human findings
High-quality sources
1 Exercise performance & recovery
2–3 g/day for ≥ 4 weeks (chronic); 3 g single dose (acute)
• 2025 double-blind crossover trial in CrossFit® athletes: + 7 % reps vs. placebo after one 3 g dose.
• 2024 systematic review/meta-analysis (12 RCTs, n=402): chronic use ↓ post-exercise blood-lactate (SMD –0.69 mmol/L) and ↑ VO₂ max by 2.2 mL/kg/min.
• 2025 meta-analysis shows lower creatine-kinase & DOMS 24 h after training.
ISRCTN Registry,
ResearchGate
2 Glucose control & metabolic markers in type 2 diabetes / pre-diabetes
1–4 g/day for 8–52 weeks
2024 dose-response meta-analysis of 36 RCTs (n=3 214) found clinically meaningful reductions in fasting glucose (–9 mg/dL), HbA1c (–0.32 %) and HOMA-IR (–0.43).
2023 ODS umbrella review corroborates ↓ insulin resistance across 41 RCTs.
PubMed,
Office of Dietary Supplements
3 Cardiovascular support (post-MI, CHF, surgery)
2–6 g/day loading → 2–3 g/day maintenance
2024 literature review reports improved LVEF and reduced arrhythmias; systematic evidence shows post-MI mortality reduction (RR 0.66) without added benefit > 3 g/day.
PMC,
MDPI
4 Male fertility (idiopathic infertility, asthenozoospermia)
2 g/day for 3–4 months
2025 meta-analysis of 19 RCTs: ↑ total sperm motility (+ 8 %), concentration (+ 6 M/mL) and morphology; 2023 narrative review affirms benefits at 2 g/day, especially combined with acetyl-L-carnitine.
PubMed,
PMC
5 Cognitive & mood support (acetylated metabolites)
1–2 g/day ALCAR equivalents
2025 Mendelian-randomization study links low acetyl-L-carnitine to poorer global cognition; 2023 review notes slowed cognitive decline and mood improvement in AD & depression trials.
PMC,
Frontiers
6 Renal anemia & muscle symptoms in hemodialysis
1–2 g IV post-dialysis or 1.5–3 g/day oral
2021 meta-analysis (18 trials) shows ↑ hemoglobin (+ 0.88 g/dL) and ↓ ESA dose (– 1 660 IU/week); 2023 review confirms benefits on anemia and muscle cramps.
PubMed,
MDPI
7 Weight & body-composition management (adjunct)
1–4 g/day for 8–30 weeks
2025 umbrella meta-analysis (8 MAs, > 16 000 participants) reports modest but significant ↓ body-weight (– 1.1 kg) and waist circumference (– 1.5 cm).
PubMed,
Office of Dietary Supplements
8 Lipid profile (dyslipidemia, NAFLD)
≥ 2 g/day for ≥ 12 weeks
2023 umbrella meta-analysis indicates ↓ LDL-C (– 8 mg/dL) and ↑ HDL-C (+ 3 mg/dL) when doses exceed 2 g/day.
Frontiers
*Doses reflect studies in L-carnitine base or its free form; L-tartrate and acetyl-L-carnitine are metabolized to the same molecule but have different pharmacokinetics.
Mechanistic highlights
- Mitochondrial fatty-acid shuttle: transports long-chain acyl-CoA into mitochondria, supporting β-oxidation and ATP production, especially during exercise.
- Acetyl buffering: maintains CoA/acetyl-CoA balance, influencing glucose–fat “fuel sparing.”
- Anti-oxidant & anti-inflammatory actions: down-regulation of CRP, TNF-α and lipid peroxidation noted in several meta-analyses.
- Sperm motility: provides acetyl-CoA for epididymal sperm maturation and scavenges ROS in seminal plasma.
- Neurotransmitter modulation: acetyl-L-carnitine donates acetyl groups for acetylcholine synthesis and epigenetic regulation of BDNF and mGlu2 expression.
Safety & practical use
- Usual supplemental range: 500 mg–3 g/day split doses with meals.
- Upper-dose tolerance: GI distress and fishy body-odor start ~ 3 g/day; seizures reported in predisposed individuals.
- Drug interactions: may potentiate warfarin; monitor INR.
- TMAO concern: gut bacteria can convert excess carnitine to trimethylamine-N-oxide—an emerging CVD risk marker, though causality remains debated.
- Populations needing medical oversight: chronic kidney disease, seizure disorders, pregnancy/lactation.
