Use of carnitine therapy in selected cases of male factor infertility: a double-blind crossover trial

Fertil Steril. 2003 Feb;79(2):292-300. doi: 10.1016/s0015-0282(02)04679-4.


Objective: To determine the efficacy of L-carnitine therapy in selected cases of male factor infertility.

Design: Placebo-controlled, double-blind, crossover trial.

Setting: University tertiary referral center.

Patient(s): One hundred infertile patients (ages 20-40 years) with the following baseline sperm selection criteria: concentration, 10-20 x 10(6)/mL; total motility, 10%-30%; forward motility, <15%; atypical forms, <70%; velocity, 10-30 micro/s; linearity, <4. Eighty-six patients completed the study.

Intervention(s): Patients underwent L-carnitine therapy 2 g/day or placebo; the study design was 2 months of washout, 2 months of therapy/placebo, 2 months of washout, and 2 months placebo/therapy.

Main outcome measure(s): Variation in sperm parameters used in the patients selection criteria, in particular, sperm motility. Excluding outliers, a statistically significant improvement in semen quality, greater than after the placebo cycle, was seen after the L-carnitine therapy for sperm concentration and total and forward sperm motility. The increase in forward sperm motility was more significant in those patients with lower initial values, i.e., <5 x 10(6) or <2 x 10(6) of forward motile sperm/ejaculate or sperm/mL.

Conclusion(s): Based on a controlled study of efficacy, L-carnitine therapy was effective in increasing semen quality, especially in groups with lower baseline levels. However, these results need to be confirmed by larger clinical trials and in vitro studies.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carnitine / therapeutic use*
  • Cross-Over Studies
  • Double-Blind Method
  • Humans
  • Infertility, Male / drug therapy*
  • Male
  • Placebos
  • Semen / drug effects
  • Semen / physiology*
  • Sperm Count*
  • Sperm Motility / drug effects*
  • Spermatozoa / abnormalities
  • Spermatozoa / drug effects


  • Placebos
  • Carnitine