Causes & Treatment Options

Possible causes: production, transport and delivery

A male fertility assessment begins with reproductive and medical history, semen analysis and an appropriate examination. Tell the team about previous pregnancies, undescended testes, testicular injury or surgery, infections, cancer treatment and difficulties with erections or ejaculation. Previous fatherhood does not guarantee that sperm health is unchanged.

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Reduced production can relate to testicular, hormonal or genetic conditions. A transport problem can mean sperm are produced but cannot reach the ejaculate because of a blockage or an absent duct. Ejaculation problems can affect delivery even when sperm production is present.

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A varicocele is enlarged veins in the scrotum. It is common: about 15% of men have one, and about 35 to 40% of men seen for infertility. Many do not need treatment. The major guidelines agree that treatment is considered for a varicocele that can be felt on examination, when semen results are abnormal; a varicocele seen only on an ultrasound scan does not need surgery for fertility. Treatment may improve pregnancy rates in selected couples, but whether it leads to more live births is uncertain. If an operation is chosen, the WHO suggests a microsurgical approach.

Azoospermia means no sperm were found in the ejaculate. The result should be confirmed on a repeat sample, with the laboratory spinning the sample (centrifugation) to search carefully for sperm, followed by specialist evaluation. Obstructive and non-obstructive causes need different investigations, including genetic tests, which the next chapter explains. Sperm retrieval is possible in some situations but cannot be promised. A low count, by contrast, is called oligozoospermia.

Referral to a urologist with male reproductive expertise or another appropriate specialist can identify treatable problems and broader health concerns. Large studies show that men with fertility problems are, on average, a little more likely to have some health problems later, especially men with no sperm in the semen. Testicular cancer is about three times more common in men with sperm problems, but it is still rare. This is a pattern in large groups, not a prediction for any one man, so a fertility assessment is a good moment for a general health check. Learn to check your testes and report any lump. Scans, genetic tests and advanced sperm tests are chosen for specific indications: European urologists recommend a scrotal scan for infertile men, while US guidance does not make it routine.

Read more: EAU guideline: Male infertility · AUA/ASRM Male Infertility guideline, amended 2024 · WHO guideline for the prevention, diagnosis and treatment of infertility (2025) · NICE NG257: Fertility problems: assessment and treatment (2026) · Persad et al. (2021), Cochrane: varicocele treatment · Kohn et al. (2018): varicoceles seen only on a scan, a review · Walsh et al. (2009): testicular cancer in men with infertility · Nedelcu et al. (2024): semen results and long-term health, a review · ASRM patient education: Male fertility evaluation

Genetics and “no sperm found”

Azoospermia has two broad causes. In obstructive azoospermia, sperm are made but a blockage or a missing duct stops them reaching the semen; this accounts for about 20 to 40% of cases, and the blockage can often be repaired or sperm retrieved. In non-obstructive azoospermia, the testes make very few or no sperm. Hormone results, testis size and the examination help tell the two apart.

A chromosome test (karyotype) is recommended for men with no sperm, and considered for very low counts. In a study of 1,663 men with azoospermia, about one in seven had a chromosome difference, most often Klinefelter syndrome (an extra X chromosome). The chance was about one in five when FSH was high, and about one in twenty when it was normal.

A Y-chromosome microdeletion test looks for small missing pieces of the Y chromosome in men with no sperm or a count of about 1 million/mL or less. The result matters: with a complete AZFa or AZFb deletion, surgery will not find sperm, and the UK’s NICE says not to operate. With an AZFc deletion, sperm are found in about half of men, and any son conceived will inherit the deletion.

Men born without the tubes that carry sperm (congenital absence of the vas deferens) usually carry a change in the cystic fibrosis gene, CFTR: about 78% did in one review. Both partners should be tested before IVF, so the risk to a baby can be explained. The gene changes found differ between ethnic groups, and standard tests look mainly for the commonest changes, so US guidance suggests wider testing or gene sequencing may be needed; ask the genetics laboratory what its test covers.

For non-obstructive azoospermia, the microscope-guided operation (micro-TESE) is the preferred method. Overall, sperm are found in about half of men, and no test before surgery reliably predicts who. In a large review, live birth was up to about 28% per ICSI cycle when sperm were found. In Klinefelter syndrome, sperm were found in about 44% of operations. Hormone treatment before surgery is not routinely recommended. Testosterone can dip for a year or two after the operation, especially in Klinefelter syndrome, and usually recovers.

Most babies born after ICSI are healthy. There is a small extra risk of birth defects compared with natural conception, partly linked to the underlying infertility: in one large Australian registry, defects were found in 9.9% of ICSI births, against 5.8% of births without fertility treatment. Sons conceived by ICSI because of their father’s low count may themselves have lower counts as adults. It is worth knowing, not a reason to avoid treatment.

When a genetic cause is found, genetic counselling before treatment is recommended, so you can understand what it means for you and any child. Donor sperm is another route some couples choose.

Read more: EAU guideline: Male infertility · NICE NG257: Fertility problems: assessment and treatment (2026) · AUA/ASRM Male Infertility guideline, amended 2024 · Donker et al. (2017): chromosome differences in 1,663 men with azoospermia · Hopps et al. (2003): sperm retrieval and Y-chromosome deletions · Yu et al. (2012): CFTR changes in men born without the vas deferens, a review · Bernie et al. (2015): micro-TESE compared with other retrieval methods, a review · Corona et al. (2019): sperm retrieval and ICSI in non-obstructive azoospermia, a review · Corona et al. (2017): sperm retrieval in Klinefelter syndrome, a review · Tharakan et al. (2022): hormone treatment before sperm retrieval, a review · Eliveld et al. (2018): testosterone after testicular sperm retrieval, a review · Davies et al. (2012): fertility treatment and birth defects · Belva et al. (2016): semen quality of young men conceived by ICSI

From assessment to a treatment plan

Some hormone conditions can be treated with specialist medication, as the guide Looking After Your Fertility explains. Selected blockages or clinical varicoceles may be managed surgically. Neither treatment is suitable for every abnormal semen result. Ask what is being treated, how long a response may take, and what happens if it does not help.

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IUI places prepared sperm into the uterus around ovulation. It still relies on further steps, including sperm reaching and fertilising an egg. The number of moving sperm after preparation and the female partner’s assessment help determine whether IUI is appropriate. For mild sperm problems, there is no good trial evidence that going straight to IVF beats IUI; the choice depends on the numbers and the woman’s age.

IVF brings eggs and prepared sperm together in the laboratory. With ICSI, an embryologist injects one sperm into a mature egg. ICSI can help in selected male-factor situations, but it does not repair all sperm problems or guarantee fertilisation, a usable embryo, pregnancy or a live birth. If sperm are normal, ICSI does not improve the chance of a baby compared with standard IVF: in a randomised trial of 1,064 couples, live births were 35% with ICSI and 31% with IVF, a difference that could be due to chance. The WHO strongly recommends IVF alone for unexplained infertility, and NICE and ESHRE also advise against ICSI when sperm are normal.

Laboratories also offer “better sperm selection” add-ons. These have not been shown to increase the chance of a baby. In the largest trial, PICSI did not increase births (27.4% against 25.2%), although a 2026 Cochrane review found it may slightly reduce miscarriage, with limited evidence. IMSI (looking at sperm under very high magnification) has not been shown to lead to more babies. The UK regulator, the HFEA, rates PICSI as having no effect, and IMSI and sperm DNA tests as unproven.

Sperm retrieval may be considered for some men with azoospermia; the chapter on genetics and “no sperm found” explains the chances. Finding sperm and achieving a live birth are different outcomes; ask for estimates relevant to your diagnosis rather than a single clinic headline.

Sperm freezing can preserve a sample for later use. Freezing does not guarantee a future pregnancy. If cancer treatment or another treatment may affect fertility, ask for a preservation discussion before it begins whenever possible; the last chapter of this guide explains how.

A useful plan includes the medical rationale, alternatives, likely timescale, costs and what success means. Donor sperm or other family-building options may also be discussed when appropriate and in line with your preferences.

Read more: AUA/ASRM Male Infertility guideline, amended 2024 · Dang et al. (2021): ICSI or IVF when sperm are normal, a randomised trial · WHO guideline for the prevention, diagnosis and treatment of infertility (2025) · NICE NG257: Fertility problems: assessment and treatment (2026) · ESHRE good practice recommendations on add-ons in reproductive medicine (2023) · Cissen et al. (2016), Cochrane: IUI, IVF and ICSI for male subfertility · Miller et al. (2019): the HABSelect trial of PICSI · Garg et al. (2026), Cochrane: advanced sperm selection techniques · Teixeira et al. (2020), Cochrane: IMSI compared with ICSI · HFEA: Treatment add-ons with limited evidence · ASRM patient education: Male fertility evaluation

HIV and conception in South Africa

Clinician sign-off pending. This chapter follows South African HIV guidance and is waiting for sign-off by an HIV clinician. Your HIV clinic’s advice comes first.

Many couples in South Africa where one or both partners live with HIV want children, and most can conceive safely. The key is the viral load: the amount of HIV in the blood. When a man living with HIV takes treatment (ART) and his viral load is undetectable, he does not pass HIV to his partner through sex. This is often summed up as U=U: undetectable equals untransmittable.

The evidence for this is strong. In a large European study of 888 couples, including 548 heterosexual couples, there were no linked HIV transmissions from a partner on treatment with a suppressed viral load, across about 58,000 times the couples had sex without condoms. A second study found the same in gay couples.

South African guidance, from the Southern African HIV Clinicians Society (2018) alongside the national guideline (2020), advises that the partner living with HIV is on treatment for at least six months, with an undetectable viral load confirmed by the clinic, before trying to conceive. Couples can then try naturally. Timing sex to the fertile days matters mainly when suppression cannot be confirmed. Viral load is checked regularly while trying, usually every three to six months.

PrEP, a daily tablet that prevents HIV, can protect the partner without HIV while the other partner’s viral load is being brought down or confirmed. It needs at least 20 days of daily use before trying, and it adds little once the partner living with HIV is confirmed undetectable. Ask the clinic about it.

Sperm washing separates sperm from the seminal fluid before IUI or IVF. It reduces, but does not completely remove, the risk. In a review of more than 11,000 treatment cycles with washed sperm, no partner became infected when the man’s viral load was suppressed. South African guidance says washing is no longer needed simply to prevent transmission when the viral load is undetectable. It is specialised and costly, and is used mainly when the viral load cannot be suppressed or when fertility treatment is needed anyway.

HIV and some HIV medicines can affect semen, for example lowering its volume and sperm movement, so a semen analysis is still worthwhile if you have been trying for a while. Fertility testing and treatment are open to people living with HIV, and both partners should be screened for other sexually transmitted infections. If the woman is the partner living with HIV, the same principle of an undetectable viral load applies, and her HIV and antenatal teams will also plan care to protect the baby.

Read more: Southern African HIV Clinicians Society: safer conception guidelines, update 2018 · South African National Department of Health: National clinical guidelines for safe conception and infertility (2020) · Rodger et al. (2016): the PARTNER study of HIV transmission · Rodger et al. (2019): the PARTNER2 study · Zafer et al. (2016): sperm washing in couples affected by HIV, a review · NICE NG257: Fertility problems: assessment and treatment (2026)

Cancer and sperm banking

Chemotherapy, radiotherapy near the pelvis or testes, and some surgery can reduce or stop sperm production, sometimes permanently. The American Society of Clinical Oncology (2025), European urologists and the UK’s NICE all say that men and boys who have gone through puberty should be offered sperm freezing (sperm banking) before treatment starts.

Ask about banking as soon as cancer is diagnosed, ideally before the first treatment, because sperm collected soon after treatment starts may carry more genetic damage. Banking usually means giving one or more samples by masturbation at a sperm bank or fertility laboratory; several samples are often advised if time allows. Not all sperm survive freezing and thawing, but frozen sperm can still be used successfully in fertility treatment.

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If no sperm are found, or a sample cannot be produced, sperm can sometimes be taken directly from the testis, including during surgery for testicular cancer. Semen is often affected even before treatment for testicular cancer: about one in four men have no sperm in their semen at diagnosis.

For teenage boys facing cancer treatment, sperm banking is possible once puberty has started, so ask the cancer team early. For boys who have not reached puberty, freezing testicular tissue is still experimental and offered only within research.

After treatment, sperm production often recovers, but after chemotherapy it can take one to four years, and it may not recover. Use contraception during treatment and for a while afterwards: European guidance says at least six months, and US guidance advises avoiding pregnancy for at least 12 months. A semen test can show whether production has returned.

Some non-cancer medicines may harm sperm production in ways that do not fully reverse; a review of medicines suggests discussing banking before long-term treatment with some immune-suppressing medicines, such as azathioprine or mycophenolate. The evidence is limited, so do not stop a prescribed medicine yourself.

In South Africa, the national infertility guideline does not cover fertility preservation for men, and access and costs vary. Ask the cancer team for a referral, and ask the sperm bank about the cost of freezing and of yearly storage, how long samples are kept, and whether your medical aid contributes. Do not let questions about cost delay the conversation: ask as soon as treatment is being planned.

Read more: ASCO guideline: Fertility preservation in people with cancer (Su et al., 2025) · EAU guideline: Male infertility · NICE NG257: Fertility problems: assessment and treatment (2026) · AUA/ASRM Male Infertility guideline, amended 2024 · Mulder et al. (2021): fertility preservation for boys and young men with cancer · WHO laboratory manual for human semen, sixth edition (2021) · Semet et al. (2017): the impact of medicines on male fertility, a review · South African National Department of Health: National clinical guidelines for safe conception and infertility (2020)

What you may be wondering

Common worries, explained carefully

The terminology, translated

Oligozoospermia

A low total sperm number or concentration.

Azoospermia

No sperm found in the ejaculate after appropriate laboratory assessment.

Varicocele

Enlarged veins in the scrotum.

IUI

Placing prepared sperm into the uterus around ovulation.

IVF

Bringing eggs and sperm together in a laboratory.

ICSI

Injecting one sperm into a mature egg during IVF.

Sperm retrieval

A procedure to obtain sperm in selected circumstances.

Cryopreservation

Freezing and storing a sample for possible later use.

Karyotype

A blood test that counts and checks the chromosomes.

Y-chromosome microdeletion

A small missing piece of the Y chromosome that can stop sperm being made.

CFTR

The cystic fibrosis gene. Changes in it are common in men born without the vas deferens.

Micro-TESE

An operation that uses a microscope to search the testes for sperm.

Viral load

The amount of HIV in the blood. Undetectable means too little to measure.

PrEP

A daily tablet that protects a man or a woman without HIV from getting it.

Videos on this guide

Videos on these questions are coming to the channel:

• Male Fertility: Questions Couples Often Forget to Ask
• Why Both Partners Need Fertility Testing

See the video schedule