Subfertility

Subfertility is reduced fertility, meaning it may take longer than expected to achieve pregnancy but conception is still possible. In men’s health, the term often comes up when sperm count, sperm motility, sperm morphology, hormone balance, sexual function, timing, or other reproductive factors are not fully optimal rather than completely absent. It matters because subfertility is common, it can affect either partner or both, and the right evaluation can often uncover treatable causes.

Table of Contents

1. What Is Subfertility?
2. Quick Takeaways
3. Subfertility vs Infertility
4. Why Subfertility Matters
5. What Subfertility Means in Men
6. Common Causes of Subfertility
7. Signs and Symptoms
8. Diagnosis and Testing
9. What’s Normal vs What’s Not?
10. What Abnormal Results May Mean
11. How to Improve Subfertility
12. Medical Treatment Options
13. Questions to Ask Your Doctor
14. Related Tests and Terms
15. Common Myths
16. FAQs
17. References

What Is Subfertility?

Subfertility means a lower-than-expected ability to conceive. It is not exactly the same as sterility. A subfertile person or couple may still be able to get pregnant naturally, but it may take longer, require better timing, or need treatment to improve the odds.

Clinically, infertility is often defined as not achieving pregnancy after 12 months of regular unprotected intercourse, or after 6 months if the female partner is 35 or older, according to guidance from the American College of Obstetricians and Gynecologists and the American Society for Reproductive Medicine. In everyday use, subfertility is often used when fertility is reduced but not absent.

In men, subfertility may relate to semen quality, sperm production, hormone issues, ejaculation problems, varicocele, genetic conditions, heat exposure, medications, or lifestyle factors. Male factors contribute to infertility in a substantial proportion of couples, as outlined by the NICHD.

At a glance

• Subfertility means reduced fertility, not necessarily permanent infertility.
• It can affect men, women, or both partners.
• Male subfertility may occur even when sexual function seems normal.
• Semen analysis is usually a core first test.
• Abnormal results do not always mean pregnancy is impossible.
• Many causes are treatable or manageable.

Quick Takeaways

• Subfertility is a delay or difficulty in conceiving, not proof that conception cannot happen.
• Male factors are common and should be assessed early, not only after female testing.
• A semen analysis is often the starting point, but it is only one piece of the fertility picture.
• Low sperm count, poor motility, abnormal morphology, hormone imbalances, and varicocele are common contributors.
• Lifestyle factors such as smoking, heavy alcohol use, obesity, anabolic steroids, poor sleep, and heat exposure can affect sperm health.
• Because sperm production takes about 2 to 3 months, improvements in habits may take time to show up in results.
• If pregnancy has not happened after 12 months, or sooner in some cases, a medical evaluation is appropriate.
• Many couples with subfertility conceive with targeted treatment, assisted reproduction, or both.

Subfertility vs Infertility

People often use these terms interchangeably, but they are not always identical in practice.

Key difference

Subfertility usually implies reduced fertility and a lower chance of conception per cycle.
Infertility is a medical diagnosis based on time trying to conceive without success.

That distinction matters because a person can be subfertile before meeting the formal definition of infertility. For example, semen parameters may be borderline, or ovulation may be irregular, yet pregnancy can still occur naturally.

Comparison table

Why Subfertility Matters

Subfertility matters because time, age, and underlying health conditions can all change the odds of conception. It can also be an early clue to broader health issues. In men, fertility problems may sometimes be associated with hormone disorders, genetic conditions, testicular disease, varicocele, metabolic disease, or prior reproductive tract injury.

A male fertility evaluation is not just about pregnancy chances. It can sometimes reveal otherwise unrecognized health concerns. Reviews in male infertility research have emphasized that abnormal semen quality can overlap with broader health risks and may justify more complete medical assessment when appropriate, including findings discussed in published literature on male infertility as a marker of health.

Early evaluation is especially important when there is:

• A history of undescended testes, testicular trauma, chemotherapy, or radiation
• Very irregular or absent menstrual cycles in the female partner
• Female age 35 or older
• Known low testosterone treatment or anabolic steroid use
• Erectile dysfunction, ejaculation issues, or prior reproductive surgery
• Two or more pregnancy losses

What Subfertility Means in Men

Male subfertility means that one or more aspects of male reproductive function may be reducing the chance of pregnancy. That can involve:

• Sperm production: too few sperm being made
• Sperm movement: sperm not swimming well enough to reach the egg
• Sperm shape: abnormal morphology, which may be associated with reduced fertilizing potential
• Semen transport: blockage or impaired delivery of sperm
• Hormonal signaling: abnormal testosterone, FSH, LH, prolactin, or thyroid function
• Sexual function: problems with erection, ejaculation, or intercourse timing
• DNA integrity: in some cases, sperm DNA damage may contribute to poorer reproductive outcomes

Importantly, a man can have no obvious symptoms and still have reduced fertility. Normal libido, normal erections, and normal ejaculation do not guarantee normal semen quality.

Common Causes of Subfertility

Subfertility can be caused by a single issue, several mild issues at once, or unexplained factors. In many couples, there are contributing factors in both partners.

Male-related causes

• Varicocele: enlarged veins around the testicle that may impair sperm production; commonly discussed in male infertility guidance from the Urology Care Foundation
• Hormone problems: low gonadotropins, thyroid disease, elevated prolactin, or other endocrine disorders
• Testicular conditions: infection, trauma, undescended testis, torsion, or previous surgery
• Genetic factors: Y chromosome microdeletions, karyotype abnormalities, or cystic fibrosis gene-related absence of the vas deferens in selected cases
• Obstruction: blockage in the reproductive tract affecting sperm transport
• Medications and substances: testosterone therapy, anabolic steroids, some chemotherapy agents, opioids, and certain other drugs
• Lifestyle factors: smoking, obesity, excessive alcohol, cannabis, poor diet, sleep problems, and sedentary habits
• Heat exposure: recurrent high heat to the testes, such as saunas, hot tubs, or occupational heat in some settings
• Environmental exposures: pesticides, solvents, heavy metals, and endocrine-disrupting chemicals may contribute in some cases, though effects vary and can be difficult to quantify

Female-related causes that may coexist

• Ovulation disorders
• Diminished ovarian reserve
• Endometriosis
• Tubal disease or blocked fallopian tubes
• Uterine abnormalities
• Age-related decline in egg quality

Shared or couple-related factors

• Infrequent intercourse or poor cycle timing
• Stress and treatment delay
• Weight-related metabolic issues
• Sexually transmitted infections affecting reproductive organs
• Unexplained subfertility despite normal basic testing

The WHO laboratory manual for the examination and processing of human semen and the ASRM male infertility resources provide widely used frameworks for assessing these issues.

Signs and Symptoms

Subfertility often has no obvious symptoms. Many men only find out during fertility testing. When symptoms are present, they may reflect an underlying cause rather than reduced fertility itself.

Possible signs in men

• Difficulty achieving pregnancy despite regular unprotected intercourse
• Low semen volume or changes in ejaculate
• Pain, swelling, or a heavy feeling in the scrotum
• History of undescended testicles or testicular injury
• Erectile dysfunction or ejaculation problems
• Reduced libido, fatigue, or other symptoms of hormone imbalance
• Decreased facial or body hair in some endocrine conditions

Still, many men with abnormal semen parameters feel completely healthy. That is why testing matters.

Diagnosis and Testing

A proper evaluation usually looks at both partners. In male fertility care, the workup often starts with a detailed history, physical exam, and semen analysis.

Typical male subfertility workup

1. Medical and fertility history
   Frequency and timing of intercourse, prior pregnancies, childhood testicular issues, medication use, testosterone use, surgeries, infections, and lifestyle habits.
2. Physical examination
   Assessment of testicular size, varicocele, signs of hormone imbalance, and possible reproductive tract abnormalities.
3. Semen analysis
   The foundational lab test for sperm concentration, total sperm number, motility, morphology, volume, pH, and other features. More than one sample is often needed because results can vary.
4. Hormone testing
   Often includes FSH, total testosterone, LH, prolactin, and sometimes estradiol or thyroid testing.
5. Scrotal or reproductive imaging
   Used selectively if varicocele, obstruction, or other structural issues are suspected.
6. Genetic testing
   Considered in specific situations, especially severe sperm deficiency or no sperm seen in semen.
7. Additional tests
   May include post-ejaculatory urinalysis for retrograde ejaculation, specialized sperm testing, or sperm DNA fragmentation in selected cases.

The AUA/ASRM guideline on diagnosis and treatment of male infertility outlines when many of these tests are appropriate.

Main fertility tests and what they assess

What’s Normal vs What’s Not?

There is no single fertility number that guarantees pregnancy. Still, semen analysis reference limits help interpret whether findings are within expected ranges in fertile men. The WHO manual is the most commonly used source for laboratory interpretation, though fertility depends on much more than one report.

Selected semen parameters commonly reviewed

These values are based on WHO reference data and are used as statistical lower reference limits, not hard cutoffs between fertile and infertile. A man below a reference limit may still conceive naturally, and a man above all limits can still experience fertility problems. See the WHO semen manual for broader context.

Important interpretation points

• One semen analysis is not enough to define long-term fertility.
• Illness, fever, abstinence interval, and lab methods can affect results.
• Mild abnormalities may not prevent natural conception.
• Severe abnormalities often warrant specialist evaluation.
• Couple fertility depends on both partners, not semen data alone.

What Abnormal Results May Mean

Abnormal fertility test results should be interpreted carefully and in context. They do not automatically predict whether pregnancy can or cannot happen.

Common semen analysis terms

• Oligozoospermia: low sperm concentration
• Asthenozoospermia: reduced sperm motility
• Teratozoospermia: low percentage of sperm with normal morphology
• Azoospermia: no sperm seen in the ejaculate
• Necrozoospermia: a high proportion of non-viable sperm
• Hypospermia: low semen volume

Possible meanings include:

• Low sperm count may reflect impaired production, hormone problems, varicocele, heat, genetics, or prior testosterone use.
• Poor motility may lower the sperm’s ability to reach the egg.
• Abnormal morphology can be associated with reduced fertilization potential, though its predictive value is often limited when viewed alone.
• Low semen volume can suggest incomplete collection, obstruction, retrograde ejaculation, or androgen-related issues.
• No sperm in semen requires more urgent specialist evaluation to distinguish production failure from blockage.

When appropriate, fertility specialists may correlate semen results with hormone levels, exam findings, genetic tests, and the reproductive history of both partners.

How to Improve Subfertility

The best strategy depends on the cause. Some changes target sperm health directly, while others improve general reproductive health and conception timing.

Practical steps that may help

1. Stop testosterone therapy or anabolic steroids if medically appropriate
   External testosterone can suppress sperm production. Men using testosterone who want fertility should speak with a qualified clinician before stopping or switching therapy.
2. Quit smoking
   Smoking has been associated with poorer semen quality in multiple studies and reviews, including evidence summarized on PubMed.
3. Moderate alcohol and avoid recreational drugs
   Heavy alcohol use and substance use may impair reproductive hormones or semen quality.
4. Reach a healthier body weight
   Obesity is linked with hormonal disruption and poorer reproductive outcomes in some men.
5. Prioritize sleep and exercise
   Poor sleep and metabolic dysfunction can affect hormone balance and overall health.
6. Avoid excessive heat to the testes
   Limit frequent hot tubs, prolonged high heat exposure, and potentially unnecessary heat stress.
7. Improve timing of intercourse
   Regular intercourse during the fertile window matters. For many couples, intercourse every 1 to 2 days around ovulation is reasonable.
8. Review medications with a clinician
   Some medicines may affect ejaculation, erections, hormones, or sperm production.
9. Address medical conditions
   Diabetes, thyroid disease, sleep apnea, and infections can all matter.

Do supplements help?

Some men ask about antioxidants, zinc, coenzyme Q10, L-carnitine, folate, selenium, or multinutrient fertility supplements. Evidence is mixed. Some studies suggest benefit for selected semen parameters in some men, but results are inconsistent and not all supplements improve live birth rates. The ASRM and fertility specialists generally recommend focusing on a clear diagnosis, correcting identifiable causes, and using supplements thoughtfully rather than assuming they are universally effective.

Because sperm develop over roughly 74 days and then mature further during transport, meaningful changes in semen quality often take about 2 to 3 months to appear.

Medical Treatment Options

Treatment depends on the diagnosis, the couple’s timeline, female partner factors, and how severe the sperm abnormality is.

Common treatment approaches

• Treating varicocele
  Varicocele repair may improve semen quality or pregnancy chances in selected men.
• Hormonal treatment
  Used in specific endocrine causes of male infertility, not as a blanket solution. Men should not start testosterone if they are trying to conceive unless they have had a fertility-specific discussion with a specialist, since testosterone can suppress sperm production.
• Managing infections or obstruction
  Some causes require medication or surgery.
• Treating erectile or ejaculation problems
  Sexual function treatment can improve the ability to conceive naturally.
• Assisted reproductive technologies
  These may include intrauterine insemination (IUI), in vitro fertilization (IVF), or intracytoplasmic sperm injection (ICSI), depending on the issue.
• Sperm retrieval procedures
  In certain men with no sperm in the ejaculate, specialists may retrieve sperm directly from the testicle or epididymis for assisted reproduction.

Treatment comparison

The best route is highly individualized. A mild semen abnormality in a younger couple may justify observation and targeted optimization, while severe sperm deficiency or female age factors may shift the plan toward faster specialist treatment.

Questions to Ask Your Doctor

• Do my test results suggest subfertility, infertility, or a normal variation?
• Should I repeat the semen analysis, and if so, when?
• Could any of my medications, supplements, testosterone use, or lifestyle habits be affecting fertility?
• Do I need hormone testing, ultrasound, or genetic testing?
• Is there evidence of varicocele, blockage, or a production problem?
• What changes are most likely to improve my chances of conception?
• How long should we try naturally before moving to treatment?
• Would IUI, IVF, or ICSI be worth discussing now?
• Do both partners need evaluation at the same time?

Related Tests and Terms

• Semen analysis: basic lab test for sperm and semen quality
• Azoospermia: no sperm in semen
• Oligozoospermia: low sperm count
• Asthenozoospermia: poor sperm movement
• Teratozoospermia: reduced normal sperm forms
• Varicocele: enlarged scrotal veins that can impair sperm production
• FSH: pituitary hormone involved in sperm production signaling
• Total testosterone: androgen hormone relevant to reproductive and sexual health
• Sperm DNA fragmentation: specialized test sometimes considered in selected cases
• IUI, IVF, ICSI: assisted reproductive techniques used based on the cause and severity

Common Myths

Myth: If I can ejaculate, I’m definitely fertile.

Not necessarily. Ejaculation does not confirm normal sperm count or sperm function.

Myth: Subfertility is usually a female issue.

No. Male factors are common and should be assessed early in a couple’s fertility evaluation.

Myth: One bad semen analysis means I’m infertile.

Not always. Results can fluctuate, and repeat testing is often needed.

Myth: Testosterone boosts male fertility.

This is a major misconception. External testosterone can reduce or shut down sperm production in many men.

Myth: Supplements alone will fix fertility problems.

Some may help selected men, but they are not a substitute for diagnosing the underlying cause.

FAQs

Can you still get pregnant with subfertility?

Yes. Subfertility means the chances may be lower or it may take longer, not that pregnancy is impossible.

Is subfertility the same as infertility?

Not exactly. Subfertility usually describes reduced fertility, while infertility is a medical diagnosis based on how long pregnancy has not occurred.

How long should we try before getting checked?

Usually after 12 months of regular unprotected intercourse, or after 6 months if the female partner is 35 or older. Some couples should seek help sooner based on medical history.

What is the first test for male subfertility?

A semen analysis is usually the first key test, often paired with history, exam, and sometimes hormone testing.

Can stress cause subfertility?

Stress alone is rarely the only explanation, but it can affect sexual function, timing, sleep, health habits, and sometimes hormones.

Can low testosterone cause subfertility?

It can in some cases, depending on the cause. But testosterone treatment itself can also suppress sperm production, which is an important distinction.

Can subfertility be temporary?

Yes. Illness, fever, medication changes, anabolic steroids, heat exposure, and lifestyle factors can cause temporary declines in sperm quality.

Does abnormal sperm morphology mean natural pregnancy cannot happen?

No. Morphology is only one part of semen analysis and is not perfectly predictive on its own.

Should both partners be tested?

Yes. Fertility is a couple-level issue, so evaluating both partners often saves time and leads to better treatment decisions.

References

• American College of Obstetricians and Gynecologists — Evaluating Infertility
• American Society for Reproductive Medicine — Infertility Topic Resources
• American Society for Reproductive Medicine — Male Infertility Topic Resources
• American Urological Association and ASRM — Diagnosis and Treatment of Infertility in Men Guideline
• World Health Organization — WHO Laboratory Manual for the Examination and Processing of Human Semen
• NICHD — What Are Some Possible Causes of Infertility?
• Urology Care Foundation — Varicoceles
• PubMed — The relationship between male infertility and men's health
• PubMed — Tobacco or marijuana use and infertility: a committee opinion