Oligospermia vs Azoospermia: Understanding Different Sperm Count Levels and Treatment

Medically reviewed by the fertility specialists at Mannat Fertility

This article is for general education and is not a substitute for professional medical advice, diagnosis, or treatment. If you have concerns about your fertility, please consult a qualified specialist.

When a couple is trying to conceive without success, one of the first and most useful investigations is a look at the male partner’s sperm. Two terms come up often in this context, and they are frequently confused: oligospermia and azoospermia. They sound similar, but they describe very different situations — and the distinction matters a great deal for what happens next.

Put simply: oligospermia means there are fewer sperm than expected in the ejaculate, while azoospermia means no sperm can be found in it at all. Understanding where a result sits between these two, and why, is the foundation for choosing the right treatment.

Quick takeaways

• Oligospermia = a low sperm count (sperm are present, just fewer than the reference range). Azoospermia = no sperm detected in the ejaculate.
• Both are findings on a semen analysis, not diagnoses in themselves — the underlying cause is what guides treatment.
• Oligospermia is often improved through lifestyle changes, treating the underlying cause, or assisted reproduction such as IUI, IVF, or ICSI.
• Azoospermia is not the same as being unable to have a biological child; in many cases sperm can be surgically retrieved and used with ICSI.
• A single abnormal result should always be confirmed with a repeat test, because sperm numbers naturally fluctuate.

What the numbers actually mean

Both conditions are identified through a semen analysis, a laboratory test that measures the volume of the sample, the concentration and total number of sperm, how well they move (motility), and their shape (morphology).

The World Health Organization publishes lower reference limits that laboratories use as a benchmark. In the most recent (2021) edition, the lower reference limit for sperm concentration is around 16 million sperm per millilitre, with a total sperm count of roughly 39 million per ejaculate. These figures represent the 5th percentile of men whose partners conceived naturally within a year — in other words, a statistical marker, not a hard line between fertile and infertile.

This is an important nuance. A value slightly below the reference limit does not mean pregnancy is impossible, and a value above it does not guarantee it. Fertility is a “couple” concept, and sperm numbers are only one part of the picture.

Oligospermia (low sperm count)

Oligospermia — also written oligozoospermia — describes a sperm concentration or total count that falls below the reference range, while sperm are still present in the sample. Clinicians often describe it loosely as mild, moderate, or severe depending on how far below the range the count sits. Severe oligospermia, where only very small numbers of sperm are found, sits closest to the azoospermia end of the spectrum.

Azoospermia (no sperm in the ejaculate)

Azoospermia means that after careful examination — including spinning the sample down (centrifugation) and examining the sediment — no sperm are seen at all. Because a single missed reading has big implications, azoospermia is only confirmed after at least two properly processed samples show the same result. You can read more about how it is worked up and managed on our page covering azoospermia treatment.

Crucially, azoospermia is divided into two broad types, and telling them apart changes everything about treatment:

• Obstructive azoospermia: Sperm are being produced normally in the testes, but a blockage — from a previous infection, surgery, vasectomy, or a congenital absence of the ducts — stops them from reaching the ejaculate.
• Non-obstructive azoospermia: The problem lies in sperm production itself, which may be reduced or absent due to hormonal, genetic, or testicular factors.

What causes low or absent sperm counts?

The two conditions share many contributing factors, and the same cause can produce a low count in one man and none at all in another. Common contributors include:

• Varicocele — enlarged veins in the scrotum, one of the most common and treatable causes of impaired sperm production.
• Hormonal imbalances affecting the signals that drive sperm production.
• Genetic factors, such as chromosomal differences or Y-chromosome microdeletions, particularly in non-obstructive azoospermia.
• Infections of the reproductive tract, which can impair production or cause scarring and blockage.
• Blockages or absence of the ducts that carry sperm.
• Lifestyle and environmental factors — smoking, excessive alcohol, obesity, heat exposure, certain medications, and anabolic steroid use.
• Prior surgery, radiation, or chemotherapy.

Because the cause directs the treatment, most men with an abnormal result are advised to complete a broader male fertility assessment rather than relying on the sperm count alone.

How each is diagnosed

A thorough evaluation usually goes beyond a single semen sample and may include:

• A repeat semen analysis, since counts vary from week to week.
• Hormone (blood) testing to assess the production pathway.
• Physical examination and scrotal ultrasound to look for a varicocele, obstruction, or structural issues.
• Genetic testing, especially where the count is very low or absent.
• A sperm DNA fragmentation test in some cases, which looks at the quality and integrity of the sperm’s genetic material rather than just the number — relevant when counts are borderline or when there has been repeated pregnancy loss or failed treatment.

Together these help distinguish, for example, an obstructive from a non-obstructive picture, or a hormonal cause from a genetic one.

Treatment options

The good news is that a low or even absent sperm count on a report is rarely the end of the road. Options broadly fall into three groups.

Treating the underlying cause

Where a specific, reversible cause is found, addressing it can improve counts over time. This might mean surgical repair of a varicocele, treating an infection, correcting a hormonal imbalance, or stopping a medication or substance that is suppressing production. Because sperm take about three months to develop, improvements are usually assessed after a repeat test some months later.

Lifestyle changes — maintaining a healthy weight, stopping smoking, moderating alcohol, and avoiding excess heat — can support sperm production and are worth pursuing alongside any medical treatment. They are not a guaranteed fix on their own, but they remove obstacles the body doesn’t need.

Assisted reproduction for low counts

When counts are low but sperm are present, assisted reproductive techniques can bridge the gap:

• Intrauterine insemination (IUI) places prepared sperm directly into the uterus, and can help in milder cases.
• In vitro fertilisation (IVF) brings egg and sperm together in the laboratory.
• Intracytoplasmic sperm injection (ICSI) takes this a step further by injecting a single sperm directly into an egg. Because it needs only a handful of viable sperm, ICSI is especially valuable in severe oligospermia.

Sperm retrieval for azoospermia

For azoospermia, the key question is whether sperm can be found in the testes even though none reach the ejaculate. In obstructive cases — and many non-obstructive ones — sperm can often be recovered directly from the epididymis or testicular tissue through minor procedures such as PESA or TESA. Retrieved sperm are then used with ICSI to fertilise eggs. This means many men diagnosed with azoospermia can still have a biological child, which is a message worth emphasising, because the diagnosis is often heard as a final verdict when it is not.

When to see a specialist

It’s reasonable to seek a fertility evaluation if:

• You’ve been trying to conceive for 12 months (or 6 months if the female partner is over 35) without success.
• There’s a known history of undescended testes, testicular injury, mumps after puberty, previous cancer treatment, or genital surgery.
• You have symptoms such as swelling or a lump in the scrotum, low libido, or difficulties with erection or ejaculation.

Seeing a specialist early doesn’t commit you to any particular treatment — it simply gets you an accurate picture, which is the single most useful thing you can have at this stage. If you’d like to talk it through, you can book an appointment with our team.

The bottom line

Oligospermia and azoospermia describe two points on the same spectrum — fewer sperm than expected versus none detected in the ejaculate — but they are findings to be explained, not sentences to be served. With a proper diagnosis of the underlying cause, a large proportion of men in both categories go on to become fathers, whether through treating the cause, assisted reproduction, or surgical sperm retrieval combined with ICSI. The most important step is a thorough, individualised evaluation.

If you have questions about your own semen analysis results or fertility, please consult a qualified fertility specialist for advice tailored to your situation.