Often, no cause can be found for a low sperm count. However, it has been associated with several genetic and non-genetic conditions including:

• A hormone imbalance such as hypogonadism.
• An inherited genetic problem such as Klinefelter's syndrome, where a man is born with an extra female chromosome.
• Undescended testicles.
• A structural problem with the male genital tract.
• A genital infection such as chlamydia, gonorrhea or prostatitis (infection of the prostate gland).
• Antibodies that attack sperm.
• Previous surgery to the scrotum or surrounding area.
• Varicoceles (dilated veins within the testicles).
• Certain medication, including testosterone replacement therapy, long-term anabolic steroid use, cancer medications (chemotherapy), some antibiotics and some ulcer medications.
• Exposure to chemicals such as pesticides.