L-carnitine is an amino acid derivative that plays a crucial role in cellular energy metabolism by transporting long-chain fatty acids into mitochondria for beta-oxidation. Scientific interest in L-carnitine’s impact on the reproductive system, particularly in male fertility, has grown over the past two decades. Several clinical studies and reviews have examined its efficacy in improving sperm quality parameters such as motility, morphology, and overall sperm count. The proposed mechanism is that L-carnitine enhances mitochondrial energy production, which is vital for sperm motility, and acts as an antioxidant, reducing oxidative stress that can damage sperm cells.

A number of randomized, placebo-controlled trials have demonstrated that L-carnitine supplementation can significantly improve sperm motility and, in some cases, increase pregnancy rates in couples experiencing male-factor infertility. For example, a meta-analysis published in Reproductive BioMedicine Online (2019) concluded that L-carnitine administration led to a significant improvement in sperm motility and concentration compared to placebo. Evidence in female reproductive health is much more limited, though some research suggests possible benefits in conditions like polycystic ovary syndrome (PCOS).

While promising, the evidence is not unanimous, and some studies report only modest or no significant effects. Overall, scientific support exists for L-carnitine’s use in male reproductive health, particularly for improving certain semen parameters, but more large-scale, high-quality studies are needed to further confirm its efficacy and clarify optimal dosing.