Male fertility and sperm health: what affects it and what you can do

Trying to conceive · Updated July 2026 · All articles

When a couple is having difficulty conceiving, most of the conversation, testing and advice tends to be directed at the woman. That reflects a significant blind spot. Research consistently shows that a male factor is involved in around half of all fertility challenges. Getting pregnant is a joint question, and sperm health matters as much as cycle health.

This article covers what a sperm analysis actually measures, which lifestyle factors have real evidence behind them, when to consider getting tested and what happens if a medical cause is found. There is no blame here, just straightforward information you can act on.

Why male fertility deserves the same attention

Around one in seven couples in the UK have difficulty conceiving. Of those, a male factor is identified in roughly 50% of cases, whether as the sole cause or alongside a female factor. Despite this, male fertility is often an afterthought until months of trying have already passed and a GP referral is finally made.

Getting a semen analysis early, or at least being willing to get one, can save a lot of time and frustration. It is a simple, non-invasive test and usually one of the first things a GP will arrange when a couple is referred for fertility assessment under NICE guidelines.

What a semen analysis measures

A semen analysis looks at several different aspects of a sperm sample. The WHO Laboratory Manual for the Examination and Processing of Human Semen (6th edition, 2021) sets the reference values used in most UK labs. Here is what each measurement means in plain terms.

• Concentration: The number of sperm in each millilitre of semen. The WHO lower reference limit is 16 million sperm per millilitre. Below this threshold can make it harder for sperm to reach and fertilise an egg, though it does not make conception impossible.
• Total count: The total number of sperm in the whole ejaculate. The WHO reference value is 39 million or above per sample. A low total count and a low concentration often go together.
• Motility: How well the sperm move. The WHO reference value is 42% or more of sperm showing any forward movement (total motility). Good motility matters because sperm need to swim through the cervix, uterus and into the fallopian tube to reach the egg. A subset called progressive motility (sperm moving actively forward) should be 30% or above.
• Morphology: The shape and structure of sperm. Using Kruger strict criteria, the WHO reference value is 4% or more of sperm having a normal form. Even in fertile men, the vast majority of sperm are structurally abnormal, which is why the threshold is set so low. Below 4% (sometimes called teratozoospermia) can affect the ability of sperm to fertilise an egg.
• Volume: The total amount of fluid produced. The WHO lower reference limit is 1.4 ml. A very low volume may suggest a blockage or problems with the glands that contribute to semen.
• pH: The acidity of the semen, normally between 7.2 and 8.0. An abnormal pH can indicate infection or a blockage of one of the ducts that carry semen.

A single semen analysis is a snapshot, not a verdict. Sperm parameters can vary considerably between samples. If a first test comes back with low values, most clinics will repeat the analysis before drawing any conclusions.

Lifestyle factors that affect sperm health

The good news is that sperm production is an ongoing process, and a number of the factors that affect it are within your control. The changes below have real evidence behind them, even if the strength of that evidence varies.

Heat

The testicles are positioned outside the body for a reason. Sperm production works best when scrotal temperature is around 2 to 4 degrees Celsius below core body temperature. Anything that raises that temperature consistently may reduce sperm quality over time.

Common sources of scrotal heat include tight underwear (particularly briefs), hot baths or jacuzzis, laptops placed directly on the lap for long periods and jobs involving prolonged sitting. The evidence here is moderate rather than definitive, and an occasional hot bath is unlikely to matter. But if you are concerned about sperm health, switching to looser underwear and giving your lap a break from the laptop is a genuinely low-cost, low-risk change.

Smoking

This has some of the strongest evidence of any lifestyle factor. Smoking is consistently associated with lower sperm count, poorer motility and a higher proportion of abnormally shaped sperm. The NHS and the Human Fertilisation and Embryology Authority (HFEA) both advise stopping smoking if you are trying to conceive. This applies to cigarettes and to other forms of tobacco.

If you smoke and want to stop, your GP can refer you to NHS Stop Smoking services, which significantly improve the chances of quitting successfully.

Alcohol

Heavy alcohol use is clearly linked to poorer sperm parameters, including reduced count, motility and morphology, as well as lower testosterone levels. The evidence for moderate drinking is less clear-cut but not reassuring: some studies show measurable effects even at lower levels of consumption. The HFEA advises keeping alcohol to a minimum when trying to conceive. Staying within NHS low-risk guidelines (no more than 14 units a week, spread across three or more days) is a reasonable starting point.

Weight

Obesity is associated with lower testosterone, higher oestrogen and poorer sperm parameters. Excess body fat can disrupt hormonal balance in ways that affect sperm production. Studies suggest that even modest weight loss in men who are overweight can improve sperm quality. This does not mean chasing a specific number on the scales, but if your weight is above a healthy range, working toward a healthier weight before and during the time you are trying to conceive is worth the effort.

Diet and antioxidants

Sperm are particularly vulnerable to oxidative stress, which is cellular damage caused by an imbalance between harmful free radicals and the body's antioxidant defences. There is growing evidence that an antioxidant-rich diet supports better sperm parameters. Nutrients with the most evidence include zinc (found in meat, shellfish and legumes), folate (leafy greens, fortified cereals), omega-3 fatty acids (oily fish, walnuts, flaxseed) and vitamins C and E (citrus fruits, nuts, seeds, peppers).

Male folic acid supplementation has some evidence behind it and is low-risk. While folic acid is most often discussed in the context of women's preconception health, some research suggests that men with higher folate intake may have improved sperm DNA integrity. It is not a guaranteed fix, but taking a standard supplement is straightforward and unlikely to cause harm. Speak to your GP if you want guidance on supplements.

Exercise

Regular moderate exercise is associated with better sperm parameters, including higher testosterone levels. You do not need to do anything extreme, a few sessions of moderate-intensity activity a week is associated with positive effects.

However, there are important caveats. Excessive endurance training, particularly very high volume running or cycling, can actually reduce sperm quality in some men. Anabolic steroids, whether used in a gym or athletic context, are one of the most potent suppressors of sperm production. They work by shutting down the body's natural testosterone production, which can result in near-zero sperm counts. Some men experience long-term or even permanent effects. If you have used or are using anabolic steroids and are trying to conceive, this should be discussed with a GP or urologist.

Stress

There is some evidence that chronic psychological stress affects sperm quality, possibly through its effects on cortisol, testosterone and oxidative stress. The association is modest and stress is difficult to measure consistently, but it is another reason to take your overall wellbeing seriously during this time. Whether that means exercise, better sleep, talking to someone or reducing work pressures, the broader picture of how you are doing matters.

Recreational drugs

Cannabis (marijuana) use is associated with reduced sperm motility and may affect the way sperm behave when they reach the egg. Evidence on count and morphology is more mixed, but the overall picture is one of harm rather than benefit. If you are trying to conceive, stopping cannabis use is advisable.

As mentioned above, anabolic steroids are in a separate category: their effect on sperm production is severe, well-established and can persist long after use stops.

The sperm production cycle: why changes take time

One of the most important things to understand about sperm health is the timeline. From start to finish, the process of producing a mature sperm cell takes approximately 74 days. This means that any changes you make today, whether stopping smoking, changing your diet or reducing alcohol, will not show up in a meaningful way in a semen analysis for roughly 2 to 3 months.

This is good news in one sense: it means the sperm you produce three months from now reflect the choices you are making now. It also means you need patience. A semen analysis done one month after making changes will not capture their full benefit. Give the changes time to work before drawing conclusions.

When to get tested

NICE guideline CG156 (Fertility: assessment and treatment for people with fertility problems) recommends that couples who have not conceived after 12 months of regular unprotected sex seek assessment, including a semen analysis. If the woman is 35 or older, this is brought forward to 6 months.

If there are known risk factors on the male side, it is reasonable to ask your GP about earlier testing rather than waiting a full year. Risk factors that make earlier assessment worthwhile include:

• previous infections such as mumps after puberty or a sexually transmitted infection (STI) that was not fully treated
• a history of undescended testicles (cryptorchidism), even if corrected in childhood
• previous testicular surgery or injury
• known use of anabolic steroids
• current chemotherapy or a history of cancer treatment
• certain medications, including some blood pressure drugs, antidepressants and antifungals

Your GP can refer you for a semen analysis on the NHS. Home semen analysis kits are also available over the counter, though they vary in what they measure and are not a substitute for a full clinical analysis if there are concerns.

Medical causes of male factor infertility

Not all male fertility challenges are down to lifestyle. A number of medical conditions can affect sperm production, transport or function, and some are highly treatable once identified.

• Varicocele: Enlarged veins in the scrotum, similar to varicose veins in the leg. This is one of the most common causes of male subfertility and is found in a significant proportion of men who present for fertility assessment. It can raise scrotal temperature and affect sperm production. Surgical treatment (varicocelectomy) may improve sperm parameters in some men, though results vary.
• Hormonal imbalances: Problems with the pituitary gland or hypothalamus can disrupt the hormonal signals that drive sperm production. Low levels of FSH or LH, or elevated prolactin, can all reduce sperm output. Blood tests can identify these patterns and some respond well to treatment.
• Previous infections: Mumps after puberty can cause orchitis (inflammation of the testicles) in a significant proportion of men, and this can permanently affect sperm production. Certain STIs, including chlamydia and gonorrhoea, can cause scarring of the reproductive tract if left untreated. Testing and treating STIs promptly is important, both for fertility and general health.
• Blockages: The tubes that carry sperm from where they are produced to where they are ejaculated can become blocked due to infection, surgery (including vasectomy) or congenital conditions. Depending on the cause and location, some blockages can be surgically repaired.
• Genetic factors: Conditions such as Klinefelter syndrome (an extra X chromosome) and Y chromosome microdeletions can significantly affect sperm production and are sometimes only identified during fertility investigation.
• Medications: Some prescription drugs can reduce sperm count or quality as a side effect. If you take regular medication and are having difficulty conceiving, it is worth asking your GP whether any of your medicines could be relevant.

If a medical cause is suspected or found, the appropriate next step is referral to a urologist or specialist in male reproductive health. Many of these conditions are treatable, or there are assisted conception options that can work around them.

What partners can do

If you are the partner of someone working on their sperm health, there are practical ways to help. Taking these steps yourself is one of them: the preconception health of both partners matters, and making the changes together is significantly easier than one person doing it alone.

Beyond the practical, it helps to approach this as a team rather than as something one person needs to fix. Fertility challenges at any stage can carry a heavy emotional weight for men, who often feel pressure to not show it. Creating space for an honest conversation, without pressure and without blame, is one of the most useful things a partner can do. A joint GP appointment, where both of you attend together from the start, can help establish from the outset that this is shared territory.

Frequently asked questions

What is a normal sperm count?

According to the WHO Laboratory Manual (6th edition, 2021), the lower reference limit for sperm concentration is 16 million sperm per millilitre, with a total sperm count of 39 million per ejaculate. A count below this does not mean conception is impossible, but it can make it harder and is worth discussing with a GP or fertility specialist.

Does wearing tight underwear affect fertility?

There is some evidence that tight underwear, particularly briefs, may raise scrotal temperature slightly and affect sperm production. The testicles need to stay 2 to 4 degrees Celsius below core body temperature to produce sperm efficiently. Switching to looser-fitting underwear is a low-risk, low-cost change that is worth trying, though the evidence is moderate rather than conclusive.

How long does it take for lifestyle changes to improve sperm?

Sperm take around 74 days to be produced and mature, which means any lifestyle changes you make today will take roughly 2 to 3 months to show a meaningful difference in a semen analysis. If you are working on improving sperm health, give the changes at least three months before expecting to see results on a test.

Can smoking affect male fertility?

Yes. Smoking is one of the factors with the strongest evidence for harming sperm quality. It is associated with lower sperm count, reduced motility and poorer morphology. The NHS and HFEA both advise stopping smoking if you are trying to conceive.

When should a man get a sperm test?

NICE guidelines (CG156) recommend that both partners are assessed if a couple has not conceived after 12 months of regular unprotected sex (or 6 months if the woman is 35 or over). A semen analysis is usually one of the first tests requested. If there are known risk factors such as previous infection, surgery or undescended testicles, earlier testing makes sense. A GP can arrange a referral, or home semen analysis kits are available.

What does low sperm motility mean?

Sperm motility refers to how well sperm move. The WHO reference value is 42% or more of sperm showing total motility (any movement). Lower motility means fewer sperm are able to swim toward the egg effectively. It can be caused by lifestyle factors such as smoking, heat exposure or anabolic steroid use, or by medical conditions. A specialist can help identify the cause and discuss options.

Related articles

• Understanding your cycle and fertile window
• Pre-conception health: folic acid, vitamins and preparing your body
• Folic acid dosage before and during pregnancy