Low sperm count (oligospermia): what counts as low and why

This page explains what a low sperm count means and what usually happens next. It cannot interpret anyone's own result: that is the work of the clinician who ordered the test.

What counts as a low sperm count

The NHS describes a low sperm count as a low amount of sperm in the semen, and says it can make it harder to conceive, though it may still be possible to conceive naturally (NHS, "Low sperm count", 2024). What is considered a low sperm count, in numbers, comes from the World Health Organization's laboratory manual. Its sixth edition, published in 2021, gives these lower reference limits, the 5th centile among men whose partners conceived within 12 months (WHO, "WHO laboratory manual for the examination and processing of human semen", 2021):

So what does low sperm count mean? A concentration below 16 million per milliliter, or a total below 39 million, is below the limit. Only 5 in 100 of the men in the reference group had a lower result. The median, the middle result in that group, gives a sense of what an average sperm count looked like in those men: 66 million per milliliter. What is a normal sperm count for one person is less clear-cut, as the next section explains, and the guide to the semen analysis sets out the other measures on a report, such as movement and shape, with the limit for each.

Why some sites say 15 million

Mayo Clinic says a sperm count is considered lower than typical below 15 million per milliliter (Mayo Clinic, "Low sperm count: symptoms and causes", 2026), and Cleveland Clinic gives a typical range of 15 million to over 200 million (Cleveland Clinic, "Oligospermia (low sperm count)", 2025). Fifteen million was the limit in the WHO manual's 2010 edition (StatPearls, "Male Infertility", 2026). The 2021 edition raised it to 16 million. The difference is small, and the range printed beside a result on a report is the one that laboratory used.

Severe oligospermia and azoospermia

Cleveland Clinic describes severe oligospermia as fewer than 5 million sperm per milliliter (Cleveland Clinic, 2025). Oligozoospermia is another name for a low concentration; the complete absence of sperm in the sample is called azoospermia (StatPearls, 2026). Azoospermia is a different finding with its own causes and tests, covered in the guide to azoospermia.

A low result is not a fertile or infertile verdict

The WHO manual states that its reference distributions cannot serve as a dividing line between fertile and subfertile men: results overlap substantially between the two groups (WHO, 2021). Some men below a limit father a child within a year, and some men above every limit are in couples who do not conceive. That is why the question of a normal sperm count to get pregnant has no single number for an answer. The chance of conceiving also depends on the partner, on age and on time; chances of getting pregnant sets out what the studies show per cycle and per year.

Signs of a low sperm count

Most low sperm count signs are not signs at all. Mayo Clinic says the main symptom is not being able to start a pregnancy, and that there might be no other clear symptoms (Mayo Clinic, 2026). The NHS says you usually find out after having tests to check your fertility (NHS, "Low sperm count", 2024).

Where an underlying condition causes the low count, Mayo Clinic lists other symptoms that may come with it (Mayo Clinic, 2026):

• trouble with sexual function, such as low sex drive or erectile dysfunction
• pain, swelling or a lump in the testicle area
• less facial or body hair, or other signs of a chromosome or hormone condition

These are signs of a low sperm count only in the sense that they can point to a cause; none of them shows the count itself. Mayo Clinic advises a checkup sooner than the usual year of trying for anyone with erection or ejaculation concerns, pain, discomfort, a lump or swelling in the testicle area, a history of testicle, prostate or sexual problems, or past groin, testicle, penis or scrotum surgery (Mayo Clinic, 2026).

What causes a low sperm count

Mayo Clinic explains that making sperm depends on the testicles and on hormone-producing parts of the brain working properly, and on the tubes that carry sperm being open; a problem anywhere along the way can lower the count. It adds that the cause often cannot be found (Mayo Clinic, 2026). It groups the known low sperm count causes in three:

• Medical causes: a varicocele, a swelling of the veins that drain the testicle, which it calls a common cause of male infertility; infections, including some sexually transmitted infections; problems with ejaculation; tumors and their treatment; undescended testicles; hormone imbalances; blocked tubes; genetic conditions such as Klinefelter syndrome; some medicines; and some surgeries, including vasectomy.
• Causes in the surroundings: long-term exposure to some industrial chemicals such as pesticides and solvents, heavy metals such as lead, radiation, and too much heat on the scrotum.
• Health, lifestyle and other causes: anabolic steroids, cocaine or marijuana use, heavy or ongoing alcohol use, smoking, long-term stress and obesity. Mayo Clinic also notes that a count can look lower than it is because of testing issues, such as a sample taken too soon after the last ejaculation or after an illness, or an incomplete sample.

The guide to male fertility covers the causes of male infertility in more depth, and how to increase sperm count, in the sense of what the evidence says about smoking, weight, alcohol, heat and other habits, is in the guide to sperm health.

Getting pregnant with a low sperm count

Can you get pregnant with a low sperm count? The NHS says it may still be possible to conceive naturally, and recommends having sex every 2 to 3 days without contraception (NHS, "Low sperm count", 2024). It also lists things that may help improve a sperm count:

• drinking no more than 14 units of alcohol a week, spread across 3 days or more
• losing weight if overweight
• stopping smoking
• wearing loose-fitting underwear, because tight underwear can raise the temperature of the testicles
• avoiding exposure to chemicals at work, such as pesticides, solvents and some heavy metals
• not taking recreational drugs such as anabolic steroids or cocaine

The NHS advises seeing a GP if you and your partner have been having regular sex without contraception for over 1 year, or 6 months if your partner is 36 or over, and have not conceived (NHS, 2024). Mayo Clinic gives a year for seeing a professional, sooner with the concerns listed above (Mayo Clinic, 2026). US and UK timings for both partners are compared in when to see a doctor about fertility, and couples who have had a child before are covered under secondary infertility.

How a low sperm count is found

The sperm count test is a semen analysis. The NHS describes it as a test of a semen sample that checks the amount of sperm, how fast they move and their shape. If it finds a possible problem, the test is usually repeated around 3 months later, and if the second test also finds a problem you are referred to a specialist for more tests, which may include blood tests, an ultrasound scan of the testicles or a urine test (NHS, "Low sperm count", 2024). Mayo Clinic notes that results are usually based on a few samples taken over time (Mayo Clinic, 2026).

How to prepare for the test, why one result is never treated as final, and what home sperm tests can and cannot measure are all in the guide to the semen analysis.

What happens next

Low sperm count treatment depends on the cause, where one is found, and on how long a couple has been trying. The NHS says that if you have a low sperm count and have not conceived after more than a year, or 6 months if your partner is 36 or over, there are NHS treatments that may help: in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI), in which eggs are fertilized with your sperm in a laboratory and put back in the womb, and sperm from a donor if the count is very low (NHS, "Low sperm count", 2024). The guide to embryo transfer describes the last step of IVF. Mayo Clinic adds that some underlying causes, such as a varicocele, can be treated with surgery (Mayo Clinic, 2026).

Supplements are often sold for a low sperm count. None of the sources on this page recommends one as a treatment, and the trial evidence on supplements is summarized in the guide to sperm health.

This guide is information, not a diagnosis or a recommendation of treatment, and it is no substitute for your own clinician. See the medical disclaimer.