Low Sperm Count: Causes, Tests, and Treatment Options Explained

A low sperm count means your concentration sits below the WHO lower reference limit of 16 million sperm per millilitre. These limits come from the 2021 WHO laboratory manual (6th edition), the global standard for reading a semen analysis. The same manual sets the other thresholds: total sperm number 39 million per ejaculate, total motility 42%, progressive motility 30%, and normal morphology 4%, with a semen volume of at least 1.4 mL.

Two words you'll hear a lot are oligozoospermia and azoospermia. Oligozoospermia, often called oligospermia, simply means the count is below 16 million per mL. Azoospermia means no sperm at all are seen in the ejaculate. It's worth knowing these numbers are the 5th percentile of fertile men, not a hard line between "fertile" and "infertile". Plenty of men below the cutoff still father children, and a single low test should always be repeated before anyone draws conclusions.

The semen analysis is the first and most important test, and the WHO 2021 manual tells your lab what "normal" looks like. The headline numbers are concentration 16 million per mL, total sperm number 39 million per ejaculate, total motility 42%, progressive motility 30%, and morphology 4% normal forms. Volume should be at least 1.4 mL.

A few practical points matter here. Sperm production takes about three months, so a result reflects how you were a season ago, not last week. Counts swing naturally with illness, fever, abstinence time, and even stress, which is why guidelines ask for two samples a few weeks apart before any diagnosis. Make sure your lab quotes the 2021 (6th edition) limits. Older reports still use the 2010 figures, where the concentration cutoff was 15 million per mL and progressive motility was 32%.

The WHO 2021 (6th edition) lower reference limits represent the 5th percentile of fertile men, not pass or fail lines.

Source: WHO laboratory manual for the examination and processing of human semen, 6th ed., 2021.

The most common identifiable cause is varicocele, a tangle of enlarged veins in the scrotum. It's found in about 15% of all men and in roughly 40% of men with abnormal semen results. The pooled blood warms the testicle, and that extra heat seems to hurt sperm production and quality.

Heat is a recurring theme. Anything that warms the testes, tight clothing, long hot baths, a laptop on the lap, or a hot work environment, can dent the count. Infections of the reproductive tract, hormonal problems such as low testosterone or thyroid issues, certain medicines, and genetic conditions all play a part too. In some men, especially with azoospermia, the cause is a blockage rather than a production problem. In an Indian tertiary-centre study of more than 2,300 men, about 37% had an abnormal semen analysis, with the combined oligo-astheno-teratozoospermia pattern being the most common finding.

A fair amount, and the good news is that this is the part you can change. Smoking is one of the clearest culprits. A large meta-analysis found that smokers had a lower sperm count, by close to 10 million per mL on average, along with reduced motility and fewer normally shaped sperm, with the heaviest smokers affected most.

Obesity, heavy alcohol, anabolic steroids and testosterone supplements (which actually shut down your own sperm production), recreational drugs, and untreated heat exposure all push numbers the wrong way. Because a full sperm cycle takes about three months, changes you make today show up on a test roughly a season later. That lag is frustrating, but it also means a genuinely better result is realistic if you give it time. Stopping smoking, losing excess weight, easing off alcohol, and keeping the testes cool are simple, evidence-backed first steps.

Sometimes the standard numbers look normal, yet pregnancy still doesn't happen or miscarriages keep recurring. This is where the sperm DNA fragmentation index, or DFI, comes in. It measures damage inside the sperm's genetic material, something a routine count, motility, and morphology test can miss entirely.

A high DFI matters. A systematic review and meta-analysis of assisted reproduction outcomes linked higher sperm DNA fragmentation with higher miscarriage rates and lower clinical pregnancy rates, although its effect on live birth was less consistent. DFI testing isn't needed for everyone. It's most useful after unexplained infertility, repeated IVF failure, or recurrent pregnancy loss. Many of the same lifestyle fixes, plus treating infection or a varicocele, can help bring an elevated DFI down.

Treatment is matched to the cause, and it usually starts with the least invasive step. Lifestyle changes and treating any infection or hormonal imbalance come first. For a clinical (palpable) varicocele with abnormal semen, surgical repair can improve semen parameters, and a meta-analysis found a pregnancy benefit specifically in this group. Repair is less helpful for small, non-palpable varicoceles, so it isn't right for everyone.

If natural conception still doesn't happen, assisted reproduction steps in. Washed sperm can be placed directly in the uterus with intrauterine insemination (IUI) when the count is mildly reduced. For low counts or poor motility, ICSI, where a single sperm is injected into each egg during IVF, is highly effective. When there's no sperm in the ejaculate, surgical sperm retrieval such as TESA or micro-TESE can recover sperm directly from the testis for use with ICSI.

Often, yes. Azoospermia means no sperm in the ejaculate, but it does not always mean no sperm in the testicle. When the cause is a blockage (obstructive azoospermia), sperm production is usually normal and retrieval is straightforward. When the testis itself produces little sperm (non-obstructive azoospermia), the question is whether any pockets of production can be found.

This is where micro-TESE, microdissection testicular sperm extraction, has changed outcomes. A systematic review reported sperm retrieval rates of roughly 43% to 63% with micro-TESE in non-obstructive azoospermia, better than conventional extraction. Any sperm found can be used with ICSI to fertilise eggs. So even a report saying "no sperm seen" is a reason to see a specialist, not to give up. An accurate diagnosis of the type of azoospermia guides everything that follows.