L-arginine
The verdict
Small/older studies suggest a role in sperm quality and IVF response; not established.
An amino acid, precursor to nitric oxide, marketed for both male sperm quality and female reproductive blood flow.
What the evidence shows
Evidence is older, smaller-scale, and narrative-review-level rather than systematic-review-level for a direct fertility outcome. One small study (34 poor responders) found fewer cancelled cycles and more eggs retrieved with L-arginine, but this is a single small trial, not a synthesis.
Evidence tier
Very limited evidence⚪ A handful of small trials, often single-source or industry-funded, not independently replicated.
Sources
Take this further
Last reviewed .