Acetyl-L-Carnitine for Male Infertility
Acetyl-L-carnitine (usually as part of a carnitine blend) reliably improves surrogate sperm measures like motility and morphology, but there is no convincing evidence it raises pregnancy or live-birth rates on its own. It rates as preliminary (Tier B) evidence and is published with a warning.
Why this grade7-layer evidence engine
Four meta-analyses and a randomized trial consistently show carnitine improves sperm parameters. A 2025 network meta-analysis ranked L-carnitine first for progressive motility (SMD 4.19, PMID 40813743), a 2025 monotherapy meta-analysis found gains in concentration, morphology, motility and testosterone (PMID 40350672), and a 175-man double-blind RCT improved progressive motility, vitality and DNA fragmentation (PMID 30873633). This replicated surrogate benefit is what earns a B rather than a fail.
The grade stops at B because the outcomes that actually matter, pregnancy and live birth, are weak and combination-dependent. Pregnancy benefit appears mainly for L-carnitine plus micronutrients (RR 3.60, PMID 36943634) or in an older, lower-quality review (OR 4.10, PMID 17392136), and live birth is essentially unstudied. Because acetyl-L-carnitine is almost always tested inside blends like Proxeed Plus, its stand-alone effect is uncertain.
Authorities are unsupportive or silent, which holds the score down. The US FDA classifies carnitine only as a nutrient supplement with no fertility claim, the EU EFSA rejected carnitine health claims, the WHO does not list it as essential, and Mayo Clinic plus the AUA/ASRM specialty guidance call fertility supplements of questionable clinical value.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.633
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (4 篇 > 0 negative)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status