Skip to content
Request quotes
Condition

Azoospermia & oligospermia

Azoospermia and oligospermia explained: causes, diagnosis, and evidence-based treatment options — with sources, not guesswork.

Also known as: oligozoospermia, zero sperm count, low sperm count

Symptoms4 listed
ICD-10N46.0
Treatable1 option
DE
Medically reviewed by Dr. Elif Yılmaz, MD, FECSM
Last reviewed 22 July 2026
✓ Clinician reviewed
Azoospermia✓ Clinician-reviewed information
Key takeaways
  • Azoospermia means no sperm at all are found in the ejaculate on a properly processed semen sample; oligospermia means sperm are present but the concentration falls below the standard reference limit.
  • Azoospermia has two fundamentally different types — obstructive (a blockage, with sperm production working normally) and non-obstructive (a problem with sperm production itself) — and telling them apart is the single most important step in diagnosis.
  • Roughly a fifth to two-fifths of azoospermia cases are obstructive, and these generally carry a better outlook for restoring or retrieving sperm.
  • A diagnosis of azoospermia is not automatically a diagnosis of permanent infertility — sperm can often still be retrieved directly from the testicle or epididymis for use in IVF/ICSI, even in many non-obstructive cases.
  • Both conditions warrant a proper, structured work-up — hormone testing, genetic testing in some cases, and sometimes imaging or biopsy — rather than assuming a single explanation from the semen result alone.

Overview

These two words describe sperm test results, but they are not the same. Oligospermia means there are sperm in the semen, but not enough. The count sits below the normal cut-off of 16 million per millilitre. Azoospermia means no sperm are found at all. To be sure, the lab spins the sample down and checks the packed pellet at the bottom. This rules out a few sperm being missed. There is also a middle state, where only a tiny number show up after spinning. That is called cryptozoospermia.

Oligospermia comes in degrees, and the degree matters. A mild dip may not stop natural conception, especially if the sperm move and are shaped well. A large drop is more likely to reduce fertility. It also more often leads to a fuller work-up, including hormone tests.

Azoospermia is the more serious finding. It affects about 10 to 15% of men checked for infertility. The first job after confirming it is to sort out which of two types it is. This split changes everything that follows. Obstructive means the testicles make sperm just fine, but a blockage stops the sperm getting out. Non-obstructive means the problem is the making of sperm itself. The two need different tests and carry a different outlook.

Obstructive azoospermia usually has the better outlook. Because sperm are being made, surgery can sometimes reopen the path. And even when it does not, sperm can often be taken straight from the tubes or the testicle for use with IVF and ICSI. Non-obstructive azoospermia is harder. But it is far from hopeless. A focused surgical search of the testicle can find small pockets of sperm in many men, even when none show up in the semen.

The key message is simple. Azoospermia and oligospermia are starting points, not endings. Many cases have a clear, treatable cause, from a varicocele to a past infection to a blockage. And where the cause cannot be reversed, modern fertility treatment often still offers a path to a biological child. A "zero sperm count" is frightening to read. In practice it is often the start of a structured, and often successful, process.

A "zero sperm count" on ejaculate analysis is not the same as zero sperm production happening anywhere in the body — sperm can often be retrieved directly from the epididymis or testicle for use in IVF with ICSI.

Types of azoospermia & oligospermia

Mild-to-moderate oligospermia
Sperm concentration below the reference limit but not severely so; may still allow natural conception, particularly with otherwise normal semen parameters.
Severe oligospermia
A significantly reduced sperm count, more strongly associated with reduced natural fertility and more likely to prompt hormonal and genetic investigation.
Cryptozoospermia
Sperm present in such extremely low numbers that they are only detectable after centrifuging the sample; a borderline state between severe oligospermia and azoospermia.
Obstructive azoospermia (OA)
Normal sperm production, but a physical blockage prevents sperm reaching the ejaculate.
Non-obstructive azoospermia (NOA)
A problem with sperm production itself, within the testicle, rather than a blockage.
How common is it?
Azoospermia is estimated to affect 10–15% of men being investigated for infertility. Of these cases, obstructive azoospermia accounts for roughly 20–40%, with the remainder being non-obstructive — the more common form overall, linked to a failure of sperm production itself rather than a blockage.
Source: pmc.ncbi.nlm.nih.gov

Symptoms

In most cases, no symptoms at all — semen appears normal in volume and colour even with no sperm present, and the finding is typically only made on semen analysis
Difficulty conceiving with a partner, often the first and only sign
In some cases, small or soft testicles, reduced body hair, or other signs of low testosterone (more associated with non-obstructive causes)
A history relevant to the cause — such as prior vasectomy, groin or scrotal surgery, undescended testicles, or significant genital infection

Causes

Genetic conditions, including Klinefelter syndrome and Y-chromosome microdeletions
Varicocele, in some cases significant enough to affect sperm production this severely
Undescended testicles in childhood
Prior testicular injury, torsion, or significant infection (such as mumps orchitis)
Damage from chemotherapy or radiotherapy
Pituitary or hypothalamic disorders affecting the hormones that drive sperm production
Vasectomy, or congenital bilateral absence of the vas deferens (often linked to a cystic fibrosis gene mutation)
Blockage from prior infection or scarring, or ejaculatory duct obstruction
Idiopathic testicular failure, where no clear cause is found despite investigation

Risk factors

Prior vasectomy
Known genetic conditions affecting fertility, or a relevant family history
A history of undescended testicles, testicular injury, or torsion
Significant testicular infection, particularly mumps orchitis
Prior chemotherapy or radiotherapy
Significant varicocele
Being a known or suspected carrier of a cystic fibrosis gene mutation
Anabolic steroid use, current or past, which can suppress natural sperm production

How it is diagnosed

Diagnosis starts with semen analysis, and a finding of azoospermia or significant oligospermia is generally confirmed with a repeat test, since results can vary between samples. For suspected azoospermia specifically, the sample is centrifuged and the concentrated pellet examined under a microscope, to rule out a small number of sperm being missed.

Once confirmed, the pathway focuses on telling obstructive from non-obstructive apart, since this determines everything that follows. A physical examination checks testicular size and consistency, and feels for the vas deferens on each side. Normal-sized testicles with normal hormones point more towards a blockage; small, soft testicles with abnormal hormones point towards a production problem. Hormone testing — particularly FSH — is central: a significantly elevated FSH generally points towards non-obstructive azoospermia.

Genetic testing (karyotype and Y-chromosome microdeletion testing) is recommended in men with non-obstructive azoospermia or very severe oligospermia. Where obstructive azoospermia is suspected, particularly if the vas deferens cannot be felt, testing for cystic fibrosis gene mutations is a standard next step. In some cases, a testicular biopsy is used both to confirm the diagnosis and, in NOA specifically, to attempt sperm retrieval at the same time.

When to see a doctor
  • A semen analysis has shown azoospermia or a significantly low sperm count
  • You and a partner have been trying to conceive for 12 months without success
  • You have a known risk factor, such as prior vasectomy, undescended testicles, or cancer treatment
  • You notice small or soft testicles, or other signs suggesting a hormonal cause
  • You are a carrier of, or have a family history of, cystic fibrosis or another relevant genetic condition

Treatment options

1Micro-TESEMicrodissection testicular sperm extraction to retrieve sperm directly from testicular tissue.
Reducing your risk
  • Where cancer treatment or another gonadotoxic therapy is planned, sperm banking beforehand is a well-established precaution against future azoospermia
  • Prompt treatment of genital infections may reduce the risk of scarring-related obstruction over time
  • Reviewing anabolic steroid use with a doctor is relevant, given its well-documented ability to suppress sperm production
  • For men considering vasectomy, understanding that it causes deliberate obstructive azoospermia — and discussing sperm banking beforehand if future fertility is a possibility — is a reasonable precaution

Common questions

Does azoospermia mean I have zero chance of having a biological child?
No, not necessarily. Even in azoospermia, sperm can often be retrieved directly from the epididymis or testicle for use in IVF with ICSI — this is true in the majority of obstructive cases and in a meaningful proportion of non-obstructive cases too. A "zero sperm count" on ejaculate analysis is not the same as zero sperm production anywhere in the body.
What is the actual difference between obstructive and non-obstructive azoospermia?
In obstructive azoospermia, the testicles produce sperm normally, but a physical blockage prevents it reaching the ejaculate. In non-obstructive azoospermia, the problem is production itself — the testicles are not making enough sperm, or any at all. This distinction is the single most important thing determined early in a work-up, because it changes treatment and outlook considerably.
Which type of azoospermia has a better outlook?
Generally, obstructive azoospermia, because sperm production itself is intact — surgical reconstruction can sometimes restore sperm to the ejaculate directly, and sperm retrieval for IVF/ICSI tends to be more consistently successful. Non-obstructive azoospermia is not hopeless — many men still achieve successful retrieval — but the obstructive category carries a more favourable starting point.
Can azoospermia be reversed?
It depends entirely on the cause. Obstructive azoospermia caused by a surgically correctable blockage — including some post-vasectomy cases — can sometimes be reversed with reconstructive surgery. Azoospermia caused by significant genetic conditions or extensive testicular damage generally cannot be reversed in the sense of restoring natural ejaculate sperm, though sperm retrieval for assisted reproduction may still be possible.
Is oligospermia less serious than azoospermia?
In terms of biology, oligospermia generally reflects a less complete disruption than azoospermia, and mild oligospermia may not significantly reduce the chance of natural conception. That said, "less serious" is not the same as "not worth investigating" — significant oligospermia deserves the same structured work-up as azoospermia, since some of the same causes apply.
What does a testicular biopsy actually show, and is it painful?
A biopsy examines a small sample of testicular tissue under a microscope to assess whether and how sperm production is occurring, and can sometimes retrieve usable sperm at the same time. It is generally done under local or general anaesthetic. Some post-procedure discomfort is expected, but it is not typically described as significantly painful — this is something to discuss with the performing specialist regarding your specific procedure.
Is genetic testing always needed for azoospermia?
Not always — it is specifically recommended in cases of non-obstructive azoospermia or very severe oligospermia, particularly where other findings suggest a production problem. For clearly obstructive cases, cystic fibrosis testing is more relevant than broader genetic testing, since a specific gene mutation is commonly linked to certain obstructive causes.
Does vasectomy always cause azoospermia?
Yes, by design — vasectomy deliberately blocks the vas deferens to prevent sperm reaching the ejaculate, and confirming azoospermia on follow-up semen analysis is exactly how its effectiveness is confirmed. This is intentional obstructive azoospermia, and it is generally, though not always, reversible with surgery if circumstances change.
Can varicocele cause azoospermia, not just reduced sperm count?
In some cases, yes — while varicocele is more commonly discussed as a cause of reduced sperm quality, a significant varicocele can, in some men, contribute to non-obstructive azoospermia. This is one reason varicocele is still assessed and sometimes treated in NOA, since correcting it occasionally results in sperm returning to the ejaculate.
If I have Klinefelter syndrome, does that always mean azoospermia?
Klinefelter syndrome is one of the more common genetic causes of non-obstructive azoospermia, but not every man with the condition has zero chance of biological fatherhood — sperm retrieval directly from the testicle succeeds in a meaningful proportion of men with Klinefelter syndrome, particularly with modern, focused techniques. This is a specific conversation to have with an experienced specialist.
How many times should a semen analysis be repeated before accepting an azoospermia diagnosis?
Current practice generally involves at least one repeat test, given natural variation in results and the possibility of a collection issue, before proceeding with the broader diagnostic pathway. Your specialist can advise on timing and any specific preparation, such as an abstinence window, that affects accuracy.
Can lifestyle changes fix azoospermia or severe oligospermia?
For some milder causes, particularly ones linked to modifiable factors like heat exposure or certain medication use, addressing the trigger can improve sperm parameters. For azoospermia caused by significant genetic conditions, extensive testicular damage, or true structural blockage, lifestyle changes alone will not resolve the issue, though general health measures remain worthwhile alongside proper assessment.
Does having azoospermia affect anything besides fertility?
For some underlying causes — particularly hormonal or genetic ones — yes, there can be broader health implications worth knowing about, such as low testosterone symptoms or, in specific genetic conditions, other associated considerations. This is part of why proper diagnosis matters beyond the fertility question alone.
What happens if sperm retrieval does not find any usable sperm?
This is a real possibility, particularly in some non-obstructive cases, and it is worth discussing honestly with a fertility specialist before the procedure — including what the realistic chances are and what alternatives exist, such as donor sperm. Retrieval technique and surgeon experience both affect success rates, which is part of why this is a decision to make with an experienced specialist.
Is azoospermia linked to a higher risk of testicular cancer?
There is a recognised, modestly elevated association between infertility — including azoospermia — and testicular cancer risk in some research, though the great majority of men with azoospermia never develop testicular cancer. This is part of why a proper testicular examination is a standard part of assessment, rather than an alarming or unusual step.
How is this different from just having a "low sperm count" mentioned casually?
"Low sperm count" is often used loosely to describe anything from mild oligospermia to complete azoospermia, but clinically these are quite different findings with different implications and next steps. Getting the specific result from an actual semen analysis — rather than relying on a general impression — is the necessary starting point for any meaningful conversation about cause or treatment.

Sources

  1. Differentiation between nonobstructive and obstructive azoospermia: then and now. Asian J Androl. 2025;27(3):298-306. https://pmc.ncbi.nlm.nih.gov/articles/PMC12112924/
  2. Rambhatla A, et al. Clinical Guidelines on the Management of Non-obstructive Azoospermia. World J Mens Health. 2026;44(1):90-105. https://pubmed.ncbi.nlm.nih.gov/40583014/
  3. Brannigan RE, et al. Updates to Male Infertility: AUA/ASRM Guideline (2024). J Urol. 2024;212(6):789-799. https://www.auanet.org/guidelines-and-quality/guidelines/male-infertility
  4. StatPearls. Azoospermia. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK578191/
  5. WHO Laboratory Manual for the Examination and Processing of Human Semen, 6th Edition. Geneva: WHO; 2021. https://iris.who.int/handle/10665/343208