The short version
- Male factors are involved in a large share of infertility. The National Institute of Child Health and Human Development (NICHD) says male factors contribute to roughly one-third of cases, female factors to another third, and the rest involve both partners or have no clear cause.
- The first test is simple: a semen analysis. The AUA/ASRM guideline says both partners should be evaluated together, and the man's workup should include a reproductive history and at least one semen analysis.
- Many causes can be treated. The most common treatable one is a varicocele, an enlarged vein in the scrotum.
- Testosterone therapy and anabolic steroids lower sperm production and are a common, avoidable cause. See our TRT and fertility guide.
When to get checked
Infertility is usually defined as not conceiving after one year of regular unprotected intercourse. NICHD reports that about 15% of couples have not conceived after one year, and about 10% after two. Doctors often suggest starting sooner, for example if the woman is 35 or older, or if either partner has a known risk factor.
Consider an earlier visit if you have:
- A history of undescended testicles, testicular injury or surgery, or cancer treatment
- Pain, swelling, or a lump in the scrotum (see our testicular cancer note)
- Low sex drive or erectile problems
- Current or past use of testosterone or anabolic steroids
A urologist, ideally one who focuses on male reproductive health, can order the testing below.
The semen analysis
A semen analysis looks at the volume of semen, how many sperm it contains, how well they move, and what share have a normal shape. You collect a sample after a short period without ejaculating, as your clinic instructs, and it is examined within about an hour. Results vary from sample to sample, so doctors often repeat an abnormal test.
The World Health Organization's laboratory manual (6th edition, published July 27, 2021) gives reference limits. Values below them are less common, but they are not a line between fertile and infertile.
| Measure | WHO 2021 lower reference limit |
|---|---|
| Sperm concentration | 16 million per mL |
| Total motility (sperm moving) | 42% |
| Progressive motility (swimming forward) | 30% |
| Normal shape (morphology) | 4% |
Many men with results under these limits do father children, and men above them can still have trouble. Your doctor will read the result alongside your history and your partner's evaluation.
Other tests
The AUA/ASRM guideline suggests hormone tests (FSH and testosterone) for men with low sex drive, erectile dysfunction, a very low sperm count or none at all, small testicles, or other signs of a hormone problem. Depending on results, doctors may also order an ultrasound or genetic testing.
What causes male infertility
NICHD lists three main groups of causes:
- Testicular problems, the most common group, which affect how the testicles make sperm. A varicocele is the most common cause of low sperm count and is present in about 40% of infertile men.
- Hormone imbalances that disrupt sperm production, including from outside testosterone.
- Blockages that stop sperm from leaving the body. A complete lack of sperm affects about 10–15% of infertile men and can come from hormones or a blockage.
In about half of cases, no cause is found.
Lifestyle, medicines, and environment
The AUA/ASRM guideline says clinicians may discuss lifestyle, medication, environmental, and workplace factors, and that the data on most of them are limited. Factors doctors commonly review include:
- Testosterone, anabolic steroids, and some other hormones. These signal the body to cut its own sperm production. This is the clearest example, and often reversible.
- Smoking, heavy alcohol use, and recreational drugs.
- Excess weight. Our fitness and metabolic health guides cover this.
- Heat to the scrotum, such as frequent hot tubs, and medications you take, which are worth reviewing with your prescriber.
- Environmental exposures. Research here is early. For example, a case-control study published October 21, 2026 linked higher urine levels of two water-disinfection byproducts to a higher risk of low sperm motility, in 135 men with the condition and 270 without. It shows an association, not a cause, and it studied men already in fertility treatment. See our October 26 briefing.
Be skeptical of "fertility supplements" sold with big promises. Our supplements guide explains how to judge the evidence.
Testosterone therapy and fertility
Outside testosterone tells the brain to stop sending the signals that make sperm, so sperm counts often fall sharply or reach zero. Sperm often return after stopping, but not always, and not on a predictable schedule. If you want children now or later, tell any prescriber before starting. Options exist that aim to protect fertility, and sperm can be banked first. Read the full comparison in our TRT and fertility guide, and see enclomiphene vs. TRT.
Testosterone therapy is also not reliable birth control, so use contraception if you do not want a pregnancy.
Treatment options
The AUA/ASRM guideline covers these treatment areas. What fits depends on the cause:
- Varicocele repair, a surgical option for selected men.
- Treating a blockage, including reversal of a vasectomy.
- Medical treatment of hormone problems, chosen by a specialist after testing.
- Sperm retrieval directly from the testicle or epididymis when the ejaculate has no sperm.
- Assisted reproduction, such as intrauterine insemination or IVF with ICSI (a single sperm injected into an egg), guided by a fertility clinic.
- Fertility preservation (sperm banking) before treatments that can harm fertility, such as chemotherapy.
Sources
- American Urological Association and American Society for Reproductive Medicine. Diagnosis and treatment of infertility in men: AUA/ASRM guideline (2020, amended 2024).
- Eunice Kennedy Shriver National Institute of Child Health and Human Development. Male infertility: condition information.
- World Health Organization. WHO laboratory manual for the examination and processing of human semen, 6th edition (2021). Lower reference limits as listed by the Manchester University NHS Foundation Trust andrology laboratory; the 42% total motility figure is from Campbell MJ, et al. Andrology. 2021, which analyzed the data behind the WHO limits.
- Ge L, et al. Urinary haloacetic acid concentrations and asthenozoospermia risk: a case-control study in China. J Expo Sci Environ Epidemiol. 2026. DOI