L-carnitine
A compound that shuttles fatty acids into mitochondria for energy. It is concentrated in the male reproductive tract and is proposed to support sperm energy metabolism and motility, and oocyte energy metabolism.
Also known as carnitine, acetyl-L-carnitine, L-carnitine-L-tartrate, levocarnitine.
At a glance
Updated monthly · checked 10 h agoL-carnitine is an amino acid marketed as a fertility supplement. It is not a fertility drug. Its computed evidence score is ~77/100. The male-fertility data are more developed than for most entries here but still limited; a plausible, low-risk adjunct rather than a proven treatment.
- Randomized trials
- 1,050
- Systematic reviews
- 492Computed
- Real product labels indexed
- 20 in the NIH DSLD
Marketed mainly for male fertility to improve sperm count and motility, and sometimes for egg quality.
The male-fertility data are more developed than for most entries here but still limited; a plausible, low-risk adjunct rather than a proven treatment.
What the evidence says
Computed from the volume and type of primary studies, not the strength of the marketing. Each figure below links to its live search.
Several small trials and meta-analyses in men suggest possible improvements in sperm motility and concentration, but the studies are small and of variable quality, and the effect on actual pregnancy rates is unclear. Data in women are sparse.
- The Role of Nutrient Supplements in Female Infertility: An Umbrella Review and Hierarchical Evidence Synthesis2024 · 15 citations
- Beneficial effects of oral antioxidant supplementation on semen quality parameters, reproductive hormones, and sperm DNA integrity in men with idiopathic oligoasthenoteratozoosperm2024 · 14 citations
- Gut microbiota-derived trimethylamine N-oxide involved in methamphetamine-induced depression-like behaviors of male mice2025 · 13 citations
- Metabolome and RNA-seq reveal discrepant metabolism and secretory metabolism profile in skeletal muscle between obese and lean pigs at different ages2025 · 13 citations
- Integrative metabolomics and transcriptomics analysis revealed specific genes and metabolites affecting meat quality of chickens under different rearing systems2024 · 13 citations
Source: europepmc+pubmed+openalex · as of Sep 25, 2026
Real product labels
Actual marketed supplement products indexed by the NIH Dietary Supplement Label Database. A product being on a shelf is not evidence it works.
- L-Carnitine 500 TabsON Optimum NutritionTablet or Pill
- L-CarnitineOff marketThorne FXCapsule
- L-CarnitineGNC Women's Ultra MegaOther (e.g. tea bag)
- L-CarnitineOff marketGNC Pro PerformanceTablet or Pill
- L-Carnitine 500 TabsON Optimum NutritionTablet or Pill
- L-Carnitine 1000Off marketGNC Total LeanCapsule
- L-CarnitineGNC Women's Ultra MegaOther (e.g. tea bag)
- L-CarnitineGNC Women'sCapsule
- Triple Strength Liquid L-Carnitine Fruit PunchOff marketGNC Total LeanLiquid
- L-CarnitineRSPCapsule
- Triple Strength Liquid L-Carnitine Fruit PunchGNC Total LeanLiquid
- L-CarnitineRSPCapsule
- L-CarnitineMyTritionCapsule
- L-CarnitineMyTritionCapsule
- L-CarnitineOff marketThorne FXCapsule
- Triple Strength L-Carnitine Liquid Fruit PunchGNC Total LeanLiquid
- L-CarnitineOff marketMetagenicsTablet or Pill
- L-Carnitine FumarateOff marketPure EncapsulationsCapsule
- L-Carnitine FumarateOff marketPure EncapsulationsCapsule
- L-Carnitine 500 mgOff marketJarrow FormulasCapsule
Source: NIH Dietary Supplement Label Database (DSLD) · as of Sep 30, 2026
What to watch for
Generally well tolerated; GI upset and a fishy body odor can occur at higher doses. May interact with thyroid medication and warfarin.
What it actually is
L-carnitine is a single, characterized compound. Its structure, molecular formula, weight, and synonyms are on its PubChem compound record.
Source: PubChem (PUG-REST)