Topic Overview

The most common cause of male infertility is low sperm count. Absence
of sperm in the semen is less common, affecting 1 out of 100 men and affecting 10 to
15 out of 100 infertile men.footnote 1

Causes of sperm count problems include:

  • Hormonal problems in the
    testicles or
    pituitary gland. The pituitary gland releases hormones
    that stimulate the testicles to produce
  • Testicular injury or
    failure, either present at birth (congenital) or associated with radiation or
    toxic chemical exposure.
  • Cancer treatment with certain kinds of
    chemotherapy or radiation.
  • Antibodies that
    attack sperm and that also may be present in semen. Sperm antibodies sometimes
    develop when a man’s sperm has been exposed to his immune system (outside of
    the testicles). This may happen after a vasectomy, an infection, or an injury
    to the testicles.footnote 2
  • Drug use (some
    prescription medicines, and marijuana and tobacco
  • Structural problems. These include:
    • A
      varicocele in the testicles.
    • Blocked
      ejaculation due to a surgical
    • Absence of a
      vas deferens (a birth defect that may be associated
      with the
      cystic fibrosis genes).
    • Retrograde
      ejaculation (the ejaculation of semen into the bladder rather than out through
      the penis).
  • Chromosomal problems (such as
    Klinefelter syndrome).
  • Genetic

See a picture of the
male reproductive system.

Related Information



  1. American Society for Reproductive Medicine and Society for Male Reproduction and Urology (2008). Evaluation of the azoospermic male. Fertility and Sterility, 90(Suppl 5): S74-S77.
  2. Fritz MA, Speroff L (2011). Male infertility. In Clinical Gynecologic Endocrinology and Infertility, 8th ed., pp. 1249-1292. Philadelphia: Lippincott Williams and Wilkins.


ByHealthwise Staff
Primary Medical Reviewer Kathleen Romito, MD – Family Medicine
Adam Husney, MD – Family Medicine
Specialist Medical Reviewer Femi Olatunbosun, MB, FRCSC – Obstetrics and Gynecology

Current as ofMarch 16, 2017