Male Infertility — Causes, Diagnosis & Treatment

Male Factor Infertility: More Common Than Most People Know

For a full overview of causes, testing, and treatment options, see our male factor infertility guide.

Male factor infertility contributes to approximately 40–50% of all infertility cases — yet fertility conversations have historically focused almost exclusively on women. According to the World Health Organization, male factor is implicated in roughly half of all cases globally, and is the sole or contributing cause in a substantial proportion of couples who struggle to conceive. This gap leads to delayed diagnosis, unnecessary female-side interventions, and significant emotional burden on couples.

Infertility is defined as the failure to achieve a clinical pregnancy after 12 months of regular, unprotected intercourse (or 6 months for women over 35). In that context, treating infertility without evaluating both partners is clinically incomplete. The first principle of any fertility evaluation should be a simultaneous assessment of both partners. A semen analysis is inexpensive, non-invasive, and provides critical diagnostic information within days — making it one of the highest-value tests in reproductive medicine.

This article covers what you need to know: how male infertility is defined and classified, how it is diagnosed, what causes it, and what treatment options are available — from lifestyle modification and surgical repair to IVF with ICSI and surgical sperm retrieval.

What Is a Semen Analysis?

A semen analysis is the cornerstone of male fertility evaluation. It measures multiple parameters that together describe the quantity, movement, and structure of sperm. The current gold-standard reference values come from the WHO 6th Edition Laboratory Manual for the Examination and Processing of Human Semen (2021), which updated the 5th edition values based on a large international dataset of fertile men.

WHO 2021 Reference Values

Source: WHO Laboratory Manual for the Examination and Processing of Human Semen, 6th Edition

What Each Parameter Means Clinically

• Volume reflects the contribution of the seminal vesicles and prostate. Low volume (< 1.4 mL) may indicate ejaculatory duct obstruction, hypogonadism, or retrograde ejaculation. Very high volume can dilute sperm concentration.
• Concentration and total count measure how many sperm are present. Total count is generally considered more informative than concentration alone, since it accounts for differences in ejaculate volume.
• Progressive motility is the percentage of sperm swimming in a forward direction — the type of motility required to traverse the female reproductive tract and reach the egg. Non-progressive motility (sperm that move but not forward) is less clinically useful.
• Total motility includes both progressive and non-progressive motility. Values below 42% define asthenospermia.
• Morphology is assessed by Kruger strict criteria, which evaluates the head, midpiece, and tail of each sperm under high magnification. Even a "normal" morphology of 4% sounds alarming, but it reflects the biology of sperm production — most sperm in a fertile ejaculate are morphologically abnormal.

Why Two Tests Are Recommended

A single abnormal result is not conclusive. Because the sperm production cycle (spermatogenesis) takes approximately 74 days, any illness, fever, medication, or environmental exposure in the preceding 2–3 months can affect a single semen sample. Clinicians recommend collecting two separate samples, 6–12 weeks apart, under standardized conditions (2–5 days of abstinence, same lab, consistent collection method) before making a definitive diagnosis or recommending treatment. Significant variation between two samples may also warrant a third.

Categories of Male Infertility

Oligospermia (Low Sperm Count)

Sperm concentration below 16 million/mL. Mild oligospermia (5–15 million/mL) often responds to IUI or IVF. Moderate oligospermia (1–5 million/mL) typically requires IVF. Severe oligospermia (< 1 million/mL) almost always requires ICSI, and cryptozoospermia (< 100,000 sperm/mL) may necessitate sperm freezing or surgical backup.

Asthenospermia (Poor Motility)

Less than 42% of sperm exhibit total motility. Causes include oxidative stress, varicocele, genital tract infection, antisperm antibodies, and structural defects of the sperm flagellum (as in primary ciliary dyskinesia). IVF with ICSI is generally recommended when motility is severely impaired.

Teratospermia (Abnormal Morphology)

Less than 4% normal forms by Kruger strict criteria. High rates of abnormal morphology are associated with sperm DNA fragmentation and reduced fertilization rates even with ICSI. Isolated teratospermia is rarely the sole reason for infertility, but it compounds other parameters.

Azoospermia (No Sperm)

Complete absence of sperm in the ejaculate — the most severe diagnosis, affecting roughly 1% of all men and 10–15% of infertile men. Classified as:

• Obstructive azoospermia (OA) — sperm are produced but cannot exit due to a blockage (vas deferens, epididymis, or ejaculatory duct). Surgical sperm retrieval success rates are high (> 95%).
• Non-obstructive azoospermia (NOA) — impaired sperm production at the testicular level. Sperm retrieval is possible in 40–60% of cases using microdissection TESE (micro-TESE).

For a complete guide to azoospermia, including all retrieval options and success rates, see our dedicated article.

Causes of Male Infertility

Male infertility has identifiable causes in the majority of cases, though a meaningful proportion remains unexplained. The following table summarizes the main causes, their prevalence among infertile men, and their underlying mechanisms.

Source: ASRM Practice Committee — Diagnostic Evaluation of the Infertile Male

Varicocele

A varicocele is a dilation of the pampiniform venous plexus within the scrotum — essentially varicose veins of the testes. It is the most common surgically correctable cause of male infertility. The primary mechanism is impaired thermoregulation: the pooled blood raises scrotal temperature, which is toxic to spermatogenesis (sperm require a temperature approximately 2–3°C below core body temperature). Varicoceles also increase reactive oxygen species (oxidative stress) and impair Leydig cell testosterone production.

Genetic Causes

Three genetic abnormalities account for most genetically caused male infertility:

1. Klinefelter syndrome (47,XXY) — the most common sex chromosome aneuploidy, affecting 1 in 600 men. Most men with Klinefelter have non-obstructive azoospermia, but sperm can sometimes be retrieved with micro-TESE.
2. Y-chromosome microdeletions — deletions in the AZFa, AZFb, or AZFc regions of the Y chromosome impair spermatogenesis. AZFa and AZFb deletions carry very poor prognosis for sperm retrieval; AZFc deletions are more variable.
3. CFTR mutations — mutations in the cystic fibrosis transmembrane conductance regulator gene cause congenital bilateral absence of the vas deferens (CBAVD), accounting for most cases of obstructive azoospermia without a history of infection.

Hormonal Causes

Hypogonadotropic hypogonadism — low FSH and LH from a pituitary or hypothalamic problem — leads to inadequate stimulation of the testes and impaired spermatogenesis. Causes include Kallmann syndrome, pituitary adenomas, and exogenous hormone use (including anabolic steroids and testosterone replacement therapy). This is one of the most treatable forms of male infertility.

Advanced Diagnostics

Beyond the standard semen analysis and hormonal panel, several specialized tests add meaningful diagnostic depth.

Sperm DNA Fragmentation (DFI)

Sperm DNA fragmentation index (DFI) measures the proportion of sperm with damaged or broken DNA strands. A DFI above 25% is associated with reduced natural conception rates, lower IUI success, and poorer IVF/ICSI outcomes. High DFI is more common in men with varicocele, unexplained infertility, recurrent pregnancy loss, and advanced age.

Multiple assays exist — TUNEL, SCSA (Sperm Chromatin Structure Assay), SCD (Sperm Chromatin Dispersion), and Comet assay. The ASRM practice committee has reviewed the evidence and supports DFI testing in select clinical scenarios, particularly after unexplained IVF failure or recurrent miscarriage. See: ASRM Practice Committee on Sperm DNA Fragmentation.

Hormonal Panel

A complete hormonal evaluation should include:

• FSH — the primary pituitary signal driving spermatogenesis. Elevated FSH suggests testicular failure (NOA); low FSH points to a central/pituitary problem.
• LH — stimulates Leydig cells to produce testosterone.
• Total and free testosterone — critical for libido, sexual function, and supporting spermatogenesis.
• Prolactin — hyperprolactinemia suppresses GnRH and can cause hypogonadism.
• Estradiol — elevated in obese men due to peripheral aromatization; can suppress gonadotropins.

Genetic Testing

Genetic testing should be offered to:

• All men with non-obstructive azoospermia or severe oligospermia (< 5 million/mL): karyotype and Y-chromosome microdeletion analysis
• Men with obstructive azoospermia (especially CBAVD): CFTR mutation analysis (with genetic counseling, as female partner should also be tested)
• Men considering surgical sperm retrieval with cryopreservation: genetic results inform prognosis and implications for offspring

Testicular Biopsy

A diagnostic biopsy may be indicated when the distinction between obstructive and non-obstructive azoospermia is unclear after non-invasive workup. In practice, many reproductive urologists proceed directly to a therapeutic biopsy (micro-TESE) that serves simultaneously as diagnostic and treatment. Biopsy findings are classified by the Johnsen score or by histologic pattern: normal spermatogenesis, hypospermatogenesis, maturation arrest, or Sertoli cell-only syndrome.

Treatment Options

Varicocele Repair

Varicocelectomy is the most commonly performed male fertility procedure. Techniques include:

• Microsurgical subinguinal varicocelectomy — the gold standard, with the lowest recurrence and complication rates
• Laparoscopic varicocelectomy — effective but requires general anesthesia
• Percutaneous embolization — radiologic approach; higher recurrence rate

Meta-analyses and the ASRM/AUA guidelines support varicocele repair in men with a palpable varicocele, at least one abnormal semen parameter, and a partner with normal or correctable fertility. A 2021 systematic review confirmed significant post-repair improvements in sperm concentration, motility, and spontaneous pregnancy rates. PubMed reference.

Improvements in semen parameters typically peak at 3–6 months post-repair (one full sperm cycle). Many couples achieve spontaneous pregnancy within 12 months of repair, avoiding the need for IVF entirely. Varicocele repair is generally recommended before ART when the clinical criteria are met, because it may improve outcomes and reduce the treatment burden.

Hormonal Therapy

For hypogonadotropic hypogonadism (low FSH and LH), gonadotropin therapy with FSH + hCG injections can restore spermatogenesis and achieve natural or IUI-assisted conception in the majority of cases — a remarkable outcome for what was once considered untreatable azoospermia.

For men with mild hypogonadism and oligospermia not caused by pituitary failure, clomiphene citrate or anastrozole (an aromatase inhibitor) may improve serum testosterone and gonadotropin levels, leading to improved semen parameters in some patients. Evidence is mixed and these are off-label uses.

Important: Exogenous testosterone (TRT, "testosterone replacement therapy") is not a fertility treatment — it suppresses FSH and LH and causes or worsens azoospermia. Men on TRT who wish to conceive must typically stop and undergo recovery, which can take 6–18 months.

IUI (Intrauterine Insemination)

IUI involves placing washed, concentrated sperm directly into the uterus around the time of ovulation. It is appropriate for mild male factor (total motile sperm count after washing ≥ 5–10 million), cervical factor, or unexplained infertility.

Success rates vary significantly by diagnosis and female age. For mild male factor infertility, live birth rates per IUI cycle are typically 8–15% in women under 35, declining with age. IUI is generally attempted for 3–6 cycles before escalating to IVF in uncomplicated cases. WHO guidelines suggest that IUI with ovarian stimulation is a reasonable first-line intervention when at least 1 million total motile sperm are available after washing.

IVF with ICSI

Intracytoplasmic Sperm Injection (ICSI) is the single most important technological advance in treating male infertility. A single viable sperm is injected directly into each mature oocyte under high magnification, bypassing the need for sperm to penetrate the egg independently. ICSI achieves fertilization rates of 60–80% across a wide range of sperm quality parameters — as long as at least one viable sperm is available.

ICSI is the preferred technique over conventional IVF insemination when:

• Total motile sperm count is < 1 million
• Morphology (Kruger strict) is < 4%
• There is a history of prior failed fertilization with conventional IVF
• Surgically retrieved sperm are used (always requires ICSI)
• Sperm DNA fragmentation is severely elevated
• Preimplantation genetic testing (PGT) is planned

For context on expected outcomes, see our breakdown of IVF success rates by age and diagnosis.

Surgical Sperm Retrieval

When ejaculation produces insufficient or no sperm, surgical retrieval techniques can obtain sperm directly from the reproductive tract or testis for use in ICSI:

• PESA (Percutaneous Epididymal Sperm Aspiration) — a needle is used to aspirate sperm from the epididymis. Suitable for obstructive azoospermia; can be performed under local anesthesia.
• TESA (Testicular Sperm Aspiration) — simple needle aspiration of testicular tissue. Lower yield than open biopsy methods.
• TESE (Testicular Sperm Extraction) — open biopsy of the testis to extract seminiferous tubules containing sperm.
• Micro-TESE (Microdissection Testicular Sperm Extraction) — the gold standard for non-obstructive azoospermia. Under an operating microscope, the surgeon identifies dilated tubules (which are more likely to contain focal spermatogenesis) and samples them selectively. Micro-TESE achieves sperm retrieval in 40–60% of NOA cases with lower complication rates than conventional TESE.

For a comprehensive guide to azoospermia and sperm retrieval — including which procedure is right for which diagnosis — see our dedicated article.

Sperm Donation

When no viable sperm can be retrieved, or in cases of severe genetic conditions that would carry significant risk to offspring, donor sperm is a highly effective alternative. Donor sperm IUI achieves pregnancy rates of 10–20% per cycle in women with no female factor; donor sperm IVF achieves rates comparable to age-adjusted IVF success benchmarks. Donor sperm also bypasses the need for any male partner procedures.

Lifestyle Factors and the Evidence

Lifestyle modification is often underemphasized in male infertility discussions. While no lifestyle change can compensate for azoospermia or genetic causes, several factors have meaningful evidence for modest improvements in semen parameters in men with mild to moderate infertility.

Heat Exposure

The testes require a temperature 2–3°C below core body temperature for optimal spermatogenesis. Prolonged heat exposure — from laptops resting on the lap, hot tubs, saunas, or occupational exposure — can temporarily impair sperm production. Studies supported by the NIH have documented scrotal temperature elevations with laptop use. The effect is reversible: avoiding heat sources allows parameters to recover within one full sperm cycle (~3 months).

Smoking

Cigarette smoking is associated with reduced sperm count, motility, and morphology, as well as increased sperm DNA fragmentation. A large analysis published in NIH's National Library of Medicine documented consistent negative effects of smoking across multiple semen parameters. Cessation is recommended at least 3 months before a fertility evaluation or treatment cycle. See the evidence at NIH.

Antioxidant Supplementation

Oxidative stress is a well-documented contributor to sperm DNA damage and poor semen parameters. Commonly used antioxidants in male fertility include:

• Coenzyme Q10 (CoQ10) — supports mitochondrial function in the sperm midpiece; some RCTs show improved motility
• Vitamin C and Vitamin E — reduce reactive oxygen species
• Zinc and Folate — involved in DNA synthesis and repair
• L-carnitine — supports sperm energy metabolism

However, a Cochrane systematic review found that while antioxidants may improve semen parameters, evidence for improved live birth rates is limited by low-quality trials. The ASRM currently considers antioxidant therapy "possibly beneficial" but does not make a strong recommendation. Men should discuss supplementation with their physician rather than self-prescribing in high doses.

Body Weight and BMI

Obesity is associated with hormonal dysregulation (elevated estradiol, reduced testosterone), increased scrotal temperature, and worsened semen parameters. ASRM guidelines recommend weight optimization as part of a comprehensive male fertility treatment plan. Meaningful improvement in semen parameters has been documented following significant weight loss.

Anabolic Steroids and Testosterone

Anabolic-androgenic steroids (AAS) — including testosterone itself when used for bodybuilding — suppress the hypothalamic-pituitary-gonadal axis. Exogenous testosterone signals the pituitary to shut down LH and FSH production, depriving the testes of the gonadotropin stimulation required for spermatogenesis. The result is severe oligospermia or azoospermia in the majority of users. Recovery after cessation can take 6–18 months and is not guaranteed. Men who have used AAS should disclose this history to their fertility specialist.

When to See a Reproductive Urologist

Many men with infertility are initially evaluated by a general urologist or their primary care physician. However, for complex or surgical cases, a reproductive urologist — a urologist who has completed subspecialty training in male infertility and andrology — provides a higher level of expertise.

You should specifically seek a reproductive urologist (rather than a general urologist) when:

• You have been diagnosed with azoospermia
• You are considering varicocele repair specifically to improve fertility (not all urologists are familiar with the fertility-specific evidence base)
• Genetic testing has identified a Y-chromosome microdeletion or Klinefelter syndrome
• You have had prior pelvic, scrotal, or retroperitoneal surgery
• You have failed hormonal treatment and surgical retrieval is being discussed
• You have had prior vasectomy and are considering reversal vs. IVF with sperm retrieval

What to Look for in a Reproductive Urologist

• Fellowship training in male infertility/andrology (beyond general urology residency)
• Experience performing micro-TESE (volume matters for surgical outcomes)
• Board certification by the American Board of Urology
• Affiliation with or access to an IVF laboratory (critical for coordination of TESE + ICSI cycles)
• Membership in the Society for Male Reproductive Urology (SMRU) or the American Society for Reproductive Medicine (ASRM)

When choosing a fertility clinic overall, look for centers with a dedicated male factor program and in-house andrology lab. See our guide to choosing a fertility clinic for a full evaluation framework, or browse IVF clinics with ICSI programs in our directory. For mild male factor, IUI clinics may be an appropriate lower-cost first step.

Diagnostic Evaluation — The Full Workup

A complete male infertility evaluation, as recommended by ASRM guidelines, includes:

1. Medical history and physical exam — testicular size and consistency, varicocele assessment, presence of vas deferens, signs of androgen deficiency
2. Two semen analyses — collected 6–12 weeks apart under standardized conditions
3. Hormonal panel — FSH, LH, total testosterone, free testosterone, prolactin, estradiol
4. Genetic testing — karyotype and Y-chromosome microdeletion analysis for azoospermia or severe oligospermia; CFTR testing for suspected CBAVD
5. Scrotal ultrasound — to assess varicocele grade, testicular volume, and epididymal abnormalities
6. Sperm DNA fragmentation testing — particularly after unexplained IVF failure, recurrent pregnancy loss, or high oxidative stress risk factors
7. Post-ejaculatory urinalysis — if low volume or retrograde ejaculation is suspected

Questions to Ask Your Doctor

When meeting with a reproductive urologist or reproductive endocrinologist, consider asking the following:

• Has my partner been evaluated simultaneously, and are we treating the couple — not just one partner?
• Should I have a sperm DNA fragmentation test, and which assay do you use?
• Am I a candidate for varicocele repair before trying IVF? What is your expected timeline for seeing improvement?
• What is the probability of finding sperm with micro-TESE given my FSH, testicular volume, and biopsy results?
• Are there lifestyle changes — stopping supplements, avoiding heat, quitting smoking — that could realistically improve my parameters in 3 months?
• If I have a Y-chromosome microdeletion, what are the implications for any male children conceived through IVF/ICSI?
• At what point would you recommend moving from IUI to IVF, or from IVF to donor sperm?
• What is the cumulative live birth rate for couples with my profile at this clinic?

This article was medically reviewed by Prof. Sandro C. Esteves, MD, PhD — Founder & Medical Director of ANDROFERT, Brazil; Chair of the WHO Male Infertility Guidelines Development Group; Honorary Professor, Aarhus University. Last reviewed April 2025.

Frequently Asked Questions

What sperm parameters indicate a need for IVF versus IUI?

As a general guide: if sperm count is above 10 million total motile sperm (TMS) and morphology is above 1–2% (Kruger strict criteria), IUI is a reasonable first-line treatment. If TMS falls below 5–10 million, or morphology is severely abnormal, IVF with ICSI offers higher success rates and is typically recommended. Below 1 million TMS, ICSI is almost always necessary.

Can varicocele treatment improve sperm parameters enough to avoid IVF?

Yes, in many cases. Studies show that varicocelectomy improves sperm count, motility, and morphology in 50–70% of men, with spontaneous pregnancy rates of 30–40% within 2 years post-surgery. For men with clinical varicocele and abnormal sperm parameters, varicocele repair is often recommended before proceeding to IVF — particularly in younger couples with no female-factor infertility.

What is ICSI and when is it needed?

Intracytoplasmic sperm injection (ICSI) is an IVF procedure where a single sperm is injected directly into each egg. It's recommended for: severe oligospermia (very low sperm count), poor sperm motility or morphology, previous fertilization failure in conventional IVF, and when sperm is retrieved surgically (TESE/PESA). ICSI fertilization rates are 70–85% of injected eggs, similar to conventional IVF in normal sperm, but significantly higher when sperm parameters are poor.

If I have azoospermia, can I still have biological children?

Possibly. It depends on the type of azoospermia. In obstructive azoospermia (OA) — caused by blockages in the reproductive tract — sperm can be retrieved surgically from the epididymis (PESA) or testicle (TESA) with high success rates (90%+). In non-obstructive azoospermia (NOA) — caused by impaired sperm production — surgical sperm retrieval (micro-TESE) finds usable sperm in 40–60% of cases. Retrieved sperm is then used with ICSI.

Does sperm DNA fragmentation affect IVF success?

High sperm DNA fragmentation (DFI >30% by TUNEL or Comet assay) is associated with lower fertilization rates, poorer embryo development, and higher miscarriage rates in IVF cycles. When DNA fragmentation is elevated, strategies include: lifestyle modifications (antioxidants, heat avoidance), testicular sperm extraction (which often has lower DFI than ejaculate), and ICSI. Not all clinics routinely test DFI — ask your RE if testing is appropriate for your situation.

How long does it take to improve sperm quality with lifestyle changes?

Sperm takes approximately 72–74 days (about 2.5 months) to develop from stem cells to mature sperm. This means lifestyle improvements take at least 3 months to fully manifest in semen analysis results. Common improvements: quitting smoking (increases count and motility by 20–40%), reducing alcohol, avoiding heat exposure (laptops, hot tubs), taking antioxidants (CoQ10, vitamin E, selenium), and optimizing weight.