Men with idiopathic subfertility (under urologist/andrologist care).
Form: L-carnitine base or tartrate
Dose: 2000–3000 mg/day
With meals
3–6 months (spermatogenesis cycle)
Why: Meta-analyses of RCTs show improvements in motility/morphology and some pregnancy outcomes.
Form: softgel
Dose: 200–300 mg/day (split with meals)
Breakfast and/or dinner
3–6 months
Why: SRMAs of RCTs show improved semen parameters; evidence for live birth remains limited.
Dose: 1000–2000 mg/day
With meals
Notes: Network meta-analyses suggest omega-3s may improve concentration; antioxidant patterns vary.