Subfertility

Subfertility: definition, meaning, causes, testing, and treatment

Subfertility means reduced fertility rather than complete infertility. In plain English, it describes a situation where pregnancy is still possible, but it is taking longer than expected or requiring more help than usual. Subfertility can affect men, women, or both partners, and it is a common reason couples seek fertility evaluation.

In men’s health, subfertility often relates to issues such as lower sperm count, reduced sperm movement, abnormal sperm shape, hormone imbalances, varicocele, sexual dysfunction, lifestyle factors, or underlying medical conditions. Importantly, subfertility is not the same as sterility. Many men diagnosed as subfertile can still conceive naturally or with treatment, depending on the cause.

At a glance: if pregnancy has not happened after 12 months of regular, unprotected sex—or after 6 months if the female partner is 35 or older—subfertility may be part of the picture, and a medical evaluation is usually appropriate.

Quick takeaways
Subfertility vs infertility
What subfertility means in men
Why subfertility matters
Signs and symptoms
Causes of male subfertility
Risk factors and lifestyle factors
How subfertility is diagnosed
What’s normal vs what’s not?
Treatment and management options
How to improve fertility naturally
When to see a doctor
Questions to ask your doctor
Related tests and terms
FAQs
References

Quick takeaways

Subfertility means reduced ability to conceive, not zero chance of pregnancy.
Male factors contribute to a substantial share of fertility problems, either alone or together with female factors.
Common male causes include low sperm count, poor motility, abnormal morphology, varicocele, hormone problems, and lifestyle factors.
A semen analysis is usually the starting test for male fertility evaluation.
One abnormal semen test does not automatically mean permanent infertility; results can vary and often need to be repeated.
Treatment depends on the cause and may include lifestyle changes, medication, surgery, or assisted reproductive technologies like IUI, IVF, or ICSI.
If pregnancy has not happened after the expected timeframe, both partners should be evaluated.
Earlier assessment is recommended if there are known risk factors such as undescended testicles, chemotherapy, erectile dysfunction, or prior reproductive surgery.

Subfertility vs infertility: what’s the difference?

People often use the terms interchangeably, but they are not exactly the same.

Term	What it means	Real-world implication
Subfertility	Reduced fertility or a lower-than-expected chance of conception	Pregnancy may still happen naturally, but it may take longer or require treatment
Infertility	Typically defined clinically as failure to conceive after 12 months of regular unprotected intercourse, or 6 months if the female partner is 35 or older	Signals the need for medical evaluation, but does not always mean pregnancy is impossible
Sterility	Complete inability to conceive naturally	Less common; may occur with absent sperm production, blocked reproductive pathways, or certain irreversible conditions

In practice, subfertility is often used when some fertility remains. A man may have measurable sperm in semen but in numbers or quality that lower the odds of conception. That is different from having no sperm at all or no reproductive potential.

What does subfertility mean in men?

Male subfertility usually means that one or more parts of the reproductive process are not working optimally. That can involve:

Sperm production: too few sperm are made
Sperm quality: sperm may move poorly or have structural abnormalities
Sperm delivery: ejaculation or reproductive tract blockage may interfere with sperm reaching the semen
Hormonal signaling: testosterone, FSH, LH, prolactin, thyroid function, and other hormonal systems can affect fertility
Sexual function: erectile dysfunction or ejaculation problems may reduce the chance of sperm reaching the egg

Male subfertility does not always come with obvious symptoms. Many men feel healthy and have normal sexual function but still have semen or hormonal abnormalities that affect their fertility potential.

Why subfertility matters

Subfertility matters because time, age, and underlying health all affect reproductive outcomes. For couples trying to conceive, delayed diagnosis can make the path longer and more stressful than it needs to be.

It also matters because subfertility can sometimes be an early clue to broader health issues. In some men, reduced fertility is linked with:

Hormonal disorders
Genetic conditions
Varicocele
Metabolic disease
Testicular dysfunction
Prior infection or inflammation
Exposure to heat, toxins, or medications

That does not mean every man with subfertility has a serious condition. It does mean a proper workup can reveal treatable problems and improve both reproductive and general health.

Signs and symptoms of subfertility

The most common “symptom” is simply difficulty achieving pregnancy. Many men with subfertility have no noticeable warning signs. When symptoms do occur, they may include:

Trouble conceiving after months of regular unprotected sex
Low semen volume
Changes in ejaculation
Erectile dysfunction
Reduced libido
Testicular pain, swelling, or a feeling of heaviness
Small testicles or changes in testicular size
History of undescended testes
Signs of low testosterone, such as low energy, low sex drive, or reduced muscle mass

Some causes of subfertility, like a varicocele, may be found on exam without causing severe symptoms. Others may only show up on lab testing or semen analysis.

Causes of male subfertility

Male subfertility has many possible causes. Sometimes there is one clear issue. In other cases, several mild factors combine to lower fertility. And in some men, the cause remains unexplained even after standard testing.

1. Sperm production problems

These are among the most common causes. The testes may produce too few sperm or sperm with lower-than-ideal function.

Oligozoospermia: low sperm concentration
Asthenozoospermia: poor sperm motility
Teratozoospermia: abnormal sperm morphology
Oligoasthenoteratozoospermia (OAT): combined abnormalities in count, movement, and shape
Non-obstructive azoospermia: no sperm in the ejaculate due to impaired production

2. Varicocele

A varicocele is an enlargement of veins in the scrotum. It can raise testicular temperature, affect blood flow, and impair sperm production or function. Varicocele is a common, potentially treatable cause of male subfertility.

3. Hormonal imbalances

Fertility depends on coordinated hormonal signaling between the brain and testes. Problems can involve:

Low or abnormal FSH and LH
Low testosterone
High prolactin
Thyroid disorders
Pituitary conditions

It is also important to note that using testosterone replacement therapy or anabolic steroids can suppress sperm production significantly, sometimes to the point of azoospermia.

4. Obstruction or delivery problems

Sometimes sperm are made but cannot get into the ejaculate effectively. Causes include:

Prior vasectomy
Congenital absence of the vas deferens
Scarring after infection or surgery
Ejaculatory duct obstruction
Retrograde ejaculation

5. Sexual function disorders

Conception can be affected by:

Erectile dysfunction
Premature ejaculation in some situations
Anorgasmia
Retrograde ejaculation
Low libido linked to hormonal or psychological causes

6. Genetic causes

Genetic factors may contribute, especially in severe sperm abnormalities or azoospermia. Examples include:

Klinefelter syndrome
Y chromosome microdeletions
CFTR gene variants associated with congenital absence of the vas deferens

7. Infections and inflammation

Past or current infections may affect fertility through scarring, inflammation, or direct testicular injury. Examples include:

Mumps orchitis
Sexually transmitted infections
Epididymitis
Prostatitis

8. Medical treatments and medications

Chemotherapy, radiation, and some medications can impair sperm production or sexual function. Depending on the drug and duration, effects may be temporary or long-lasting.

9. Environmental and occupational exposures

Potential contributors include:

Excess heat exposure
Pesticides
Heavy metals
Industrial chemicals
Solvents
Radiation exposure

10. Unexplained male subfertility

Sometimes standard tests are near normal or only mildly abnormal, yet conception still does not happen. This is often called unexplained male factor subfertility or part of unexplained infertility as a couple. More specialized testing may or may not identify a reason.

Risk factors and lifestyle factors

Lifestyle does not explain every case, but it can meaningfully affect fertility potential.

Factor	Possible effect on fertility	Potential next step
Smoking	May worsen sperm count, motility, DNA integrity, and overall semen quality	Stop smoking and avoid secondhand smoke
Heavy alcohol use	Can affect hormones, sexual function, and sperm production	Reduce intake or stop
Obesity	Associated with hormonal disruption, heat effects, and reduced semen quality	Weight management and metabolic evaluation
Heat exposure	Frequent hot tubs, saunas, or occupational heat may impair sperm production	Reduce exposure where possible
Anabolic steroids or testosterone therapy	Can suppress natural sperm production	Discuss alternatives with a specialist before stopping or changing therapy
Poor sleep and high stress	May affect hormones, sexual function, and health behaviors	Improve sleep and manage stress
Recreational drugs	Some substances may impair sperm or sexual function	Stop use and seek support if needed

How subfertility is diagnosed

Diagnosing subfertility involves looking at the couple as a whole, but male evaluation is essential. Too often, workup starts only with the female partner, which can delay answers.

Typical male fertility evaluation

Medical and reproductive history
Past conceptions, duration of trying to conceive, timing and frequency of intercourse, medications, surgeries, childhood history, infections, and exposures all matter.
Sexual history
Erections, ejaculation, libido, and any pain or difficulty with intercourse should be assessed.
Physical examination
A clinician may examine the testes, epididymis, vas deferens, penis, and check for varicocele or signs of hormonal issues.
Semen analysis
This is usually the key first-line test.
Hormone testing
Often includes testosterone, FSH, LH, and sometimes prolactin and thyroid testing.
Additional tests when indicated
These may include scrotal ultrasound, genetic testing, post-ejaculatory urine testing, specialized sperm function testing, or sperm DNA fragmentation testing in select cases.

Semen analysis: the main test

A semen analysis evaluates several features of the ejaculate and sperm. Because sperm parameters can change over time, at least two tests spaced apart are often recommended if the first result is abnormal.

Common semen analysis measures include:

Semen volume
Sperm concentration
Total sperm number
Progressive motility
Total motility
Morphology
Vitality
pH and white blood cells in some settings

What’s normal vs what’s not?

Fertility testing is not simply “normal” or “abnormal.” Many men with borderline semen values can still conceive naturally, while some men with values inside reference ranges still have fertility difficulties. Still, reference ranges help guide interpretation.

Common semen analysis reference concepts

Measure	What it describes	Why it matters
Semen volume	Amount of ejaculate	Very low volume may suggest obstruction, incomplete collection, or ejaculation issues
Sperm concentration	Number of sperm per milliliter	Lower concentration can reduce the probability of sperm reaching the egg
Total sperm number	Total sperm in the whole ejaculate	Reflects overall sperm output
Motility	How well sperm move	Sperm need adequate movement to travel through the reproductive tract
Morphology	Shape and structure of sperm	Abnormal morphology can be associated with reduced fertilizing potential, though interpretation can be complex
Vitality	Percentage of live sperm	Useful when motility is very low

How doctors interpret an abnormal result

An abnormal semen analysis does not automatically equal infertility. Doctors usually look at:

Whether the abnormality is mild, moderate, or severe
Whether it appears on repeat testing
Your age and your partner’s age
How long you have been trying to conceive
Whether there are additional issues, like varicocele or low testosterone
Whether the female partner has any fertility factors as well

Examples of findings that may suggest male subfertility

Low sperm count or total sperm number
Poor progressive motility
Low normal-form sperm percentage
Very low semen volume
No sperm seen in the ejaculate
Abnormal hormone levels
A palpable varicocele with abnormal semen parameters

Treatment and management options

The best treatment for subfertility depends on the cause, severity, test results, the couple’s timeline, age, and reproductive goals. Some men improve with relatively simple changes. Others may need advanced fertility care.

1. Lifestyle optimization

When lifestyle factors are contributing, clinicians may recommend:

Stopping smoking and vaping
Reducing or avoiding heavy alcohol use
Addressing obesity and metabolic health
Improving sleep
Reducing heat exposure
Stopping anabolic steroids or non-prescribed hormones
Reviewing medications with a doctor

Because sperm development takes roughly 2 to 3 months, improvements in semen parameters may not show up right away.

2. Medical treatment

Medication may help in selected situations, for example:

Treating hormonal disorders
Managing thyroid disease or elevated prolactin
Using fertility-directed hormonal therapy in men with specific endocrine causes
Treating infections when clinically indicated

Not every supplement or medication marketed for male fertility is evidence-based. Men considering fertility supplements should discuss them with a clinician, especially if they take other medications or have medical conditions.

3. Varicocele repair

If a clinically significant varicocele is present along with abnormal semen parameters or infertility, repair may improve semen quality in some men and may increase the chance of conception. It is not appropriate for every case, but it is one of the more common male fertility procedures.

4. Surgical or procedural treatment for obstruction

If the problem is a blockage or prior vasectomy, options may include:

Microsurgical reconstruction
Sperm retrieval procedures
Use of retrieved sperm in IVF/ICSI

5. Treatment for ejaculation or sexual function problems

Depending on the issue, management may involve:

Treatment for erectile dysfunction
Addressing low testosterone carefully, especially when fertility is a goal
Therapy for psychosexual issues
Approaches for retrograde ejaculation or anejaculation

6. Assisted reproductive technologies (ART)

ART can help when natural conception is less likely or when time matters.

Treatment	How it works	When it may be used
IUI (intrauterine insemination)	Prepared sperm are placed into the uterus around ovulation	Mild male factor, unexplained infertility, or cervical factors in some couples
IVF (in vitro fertilization)	Eggs are fertilized in a lab and embryo transfer follows	Moderate to severe infertility, tubal factors, or when other methods have failed
ICSI (intracytoplasmic sperm injection)	A single sperm is injected into an egg during IVF	Severe male factor infertility, low sperm count, poor motility, or surgically retrieved sperm

How to improve fertility naturally

Natural improvement is possible in some cases, especially when modifiable factors are involved. That said, “natural” does not mean enough for every situation, and severe male factor infertility usually needs formal medical care.

Practical steps that may support male fertility

Stop smoking
Smoking is consistently linked with poorer semen quality and oxidative stress.
Maintain a healthy body weight
Weight loss may improve hormonal balance and reproductive function in some men.
Exercise regularly, but avoid extremes
Moderate activity supports overall health. Overtraining, extreme caloric deficit, or steroid use can work against fertility.
Limit alcohol and avoid recreational drugs
Heavy use can affect both sperm and sexual function.
Protect sleep
Poor sleep may affect hormones, energy, and libido.
Reduce excessive heat exposure
Hot tubs, saunas, and certain work environments may matter, especially if exposure is frequent.
Review medications and hormones
Some drugs and testosterone therapy can reduce sperm production.
Eat a balanced diet
There is no single fertility diet, but a nutrient-dense pattern that supports metabolic health is generally beneficial.
Time intercourse appropriately
Regular intercourse every 1 to 2 days during the fertile window usually gives the best chance of conception.

Because sperm take time to develop, a good rule of thumb is to reassess after about 3 months of sustained changes, unless your clinician advises a different timeline.

When to see a doctor about subfertility

Seek evaluation if:

You have been trying to conceive for 12 months without success
You have been trying for 6 months and the female partner is 35 or older
You have known risk factors such as undescended testicles, prior chemotherapy, testicular surgery, varicocele, ejaculation problems, or testosterone use
You have very low semen volume, painful ejaculation, or erectile dysfunction affecting conception
You have a history of mumps orchitis, STIs, pelvic surgery, or trauma
You have signs of hormone imbalance such as low libido, breast enlargement, or reduced body hair

Earlier assessment can save time and may uncover reversible causes.

Questions to ask your doctor

Do my test results suggest subfertility, infertility, or a specific male factor diagnosis?
Should I repeat my semen analysis, and how should I prepare for it?
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 or an obstruction?
What treatment options make sense in my case?
How long should we try lifestyle changes before repeating testing?
Would we be better served by seeing a reproductive urologist or fertility specialist now?

If you are researching subfertility, you may also come across these related terms:

Semen analysis: lab test measuring sperm count, motility, morphology, and more
Oligozoospermia: low sperm concentration
Asthenozoospermia: low sperm motility
Teratozoospermia: abnormal sperm morphology
Azoospermia: no sperm in the ejaculate
Varicocele: enlarged scrotal veins that may affect sperm production
FSH, LH, testosterone, prolactin: hormones commonly checked in male fertility workups
Sperm DNA fragmentation: a specialized test used selectively in some fertility evaluations
IUI, IVF, ICSI: assisted reproductive technologies used to help achieve pregnancy

Common myths about subfertility

Myth: If I can get an erection, my fertility must be normal.

Not necessarily. Sexual function and fertility are related but not identical. A man can have normal erections and still have significant sperm abnormalities.

Myth: Subfertility always means the problem is severe.

No. Some cases are mild and improve with time, treatment, or lifestyle changes. Others are more complex. The term describes reduced fertility, not a fixed outcome.

Myth: If I already fathered a child, I cannot have male fertility problems now.

Secondary subfertility is real. Fertility can change over time due to age, health conditions, surgery, medications, hormone use, or new exposures.

Myth: Testosterone therapy boosts fertility because it raises testosterone.

This is a common misunderstanding. Exogenous testosterone often suppresses sperm production, sometimes dramatically.

Myth: One semen test tells the whole story.

Semen parameters fluctuate. Abnormal results often need confirmation and interpretation in context.

Frequently asked questions

Can a subfertile man still get someone pregnant?

Yes. Subfertility means pregnancy is still possible, but the chances may be lower or it may take longer. The actual likelihood depends on the cause and severity.

How long does subfertility mean it takes to conceive?

There is no single timeline. Clinically, fertility evaluation is usually recommended after 12 months of trying, or after 6 months if the female partner is 35 or older. Some couples conceive naturally after that point, but the delay warrants assessment.

Is subfertility reversible?

Sometimes. It depends on the cause. Lifestyle-related issues, hormone problems, varicocele, certain obstructions, and some ejaculation disorders may improve with treatment. Other causes may be permanent but still manageable with assisted reproduction.

What is the most common test for male subfertility?

The most common first test is a semen analysis. It looks at sperm count, motility, morphology, semen volume, and other markers.

Does low testosterone mean I am subfertile?

Not always, but low testosterone can be associated with fertility issues in some men. Fertility depends on more than testosterone alone, and some men with low testosterone can still produce sperm. Proper hormone testing is important.

Can stress cause subfertility?

Stress alone is rarely the only cause, but it can contribute indirectly by affecting sleep, libido, erections, lifestyle habits, and hormonal balance. Stress can also make the process of trying to conceive much harder emotionally.

Can being overweight affect male fertility?

Yes, excess body weight can affect hormones, inflammation, metabolic health, and semen quality. Improving weight and overall health may help some men.

Should both partners be tested at the same time?

Usually, yes. Fertility is a couple issue, and male and female factors may exist together. Evaluating both partners can reduce delays and improve planning.

Can supplements fix subfertility?

Not reliably on their own. Some supplements are marketed for sperm health, but evidence varies and they are not a substitute for diagnosis. If a serious male factor issue exists, supplements alone may not be enough.

When should I see a reproductive urologist?

Consider a reproductive urologist if you have abnormal semen results, no sperm in the ejaculate, hormone abnormalities, a suspected varicocele, history of testicular problems, prior vasectomy, or ongoing difficulty conceiving.

References

American Urological Association (AUA) and American Society for Reproductive Medicine (ASRM). Male Infertility clinical guidance and evaluation recommendations.
World Health Organization. WHO Laboratory Manual for the Examination and Processing of Human Semen.
ASRM Practice Committee. Guidance on evaluation and treatment of infertility.
National Institute for Health and Care Excellence (NICE). Fertility problems: assessment and treatment.
European Association of Urology (EAU). Guidelines on Sexual and Reproductive Health, including male infertility.
Centers for Disease Control and Prevention (CDC). Infertility and reproductive health resources.