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Nov 2, 2026
When fertility is discussed, the focus is often on the woman's body, ovulation and menstrual cycle. But a pregnancy needs both an egg and a sperm. In fact, male factors contribute to around half of all cases where couples have fertility problems.
Despite this, many men know very little about their own fertility. What affects sperm quality? How are sperm produced? Does age affect fertility in men? And can sperm quality be improved through lifestyle changes?
In this article we go through how male fertility works, what can cause male infertility, how sperm quality is tested and which factors can affect the chance of having a baby.
Male fertility depends on the number, movement and shape of the sperm. Male factors contribute to around half of all cases of infertility, yet most men have no symptoms. New sperm take about 70 to 75 days to form, so the effect of lifestyle changes such as stopping smoking, drinking less alcohol and a healthy weight shows in a semen analysis after two to three months at the earliest. A semen analysis shows where you stand.
The most important factor in male fertility is the sperm's ability to fertilise an egg. For a pregnancy to happen, there need to be enough sperm, they need to move well and they need to be able to deliver their genetic material to the egg.
Even though only one sperm is needed to fertilise an egg, a normal ejaculation contains millions of sperm. The reason is simple: the way to the egg is long and challenging. Most sperm are lost already on the journey through the woman's reproductive system. By the time the sperm reach the fallopian tube, where fertilisation usually takes place, only a small share of those that were in the semen remain.
In the end, only one sperm manages to enter the egg and start the process that can lead to a pregnancy. That is why both sperm count and sperm quality play a decisive role in fertility.
Unlike women, who are born with all their eggs, men produce new sperm throughout their lives.
A healthy man can produce millions of sperm every day. Production takes place in the testicles and is controlled by an interplay between several hormones, above all FSH, LH and testosterone. These hormones are regulated by the pituitary gland and the hypothalamus in the brain.
Sperm develop from stem cells in the testicles and go through a long maturation process before they become fully functioning reproductive cells. They are then stored in the epididymis, where they continue to mature.
During sexual arousal, the sperm mix with fluid from the seminal vesicles and the prostate. This mixture is called semen. On ejaculation, the sperm travel through the woman's vagina, cervix and womb on towards the fallopian tubes, where they can fertilise an egg.
The whole process, from stem cell to fully developed sperm, takes about 70 to 75 days. This means that lifestyle changes or treatments aimed at improving sperm quality usually do not take effect until after about two to three months.
Sperm can survive for up to five days in the woman's reproductive organs. That is why sex several days before ovulation can still lead to pregnancy.
Outside the body, however, sperm survive only a short time, because they quickly dry out and lose their ability to move.
There are many factors that can affect sperm production and therefore fertility. Read also about infertility in both women and men.
Essentially, there are three types of problem:
Many men do not notice that their fertility is reduced. Problems are usually discovered only when the couple seeks help because pregnancy has not happened and has a fertility assessment.
Underlying causes can be genetic factors, hormonal disorders, infections, injuries to the testicles, chronic diseases or certain medicines.
The risk of fertility problems may be higher in men who have, for example, had surgery on the scrotum, had testicular torsion, infections in the testicles or prostate, received chemotherapy or radiotherapy, or have problems with erection or ejaculation.
A common cause of low sperm counts today is testosterone taken from outside the body, for example as hormone treatment, performance-enhancing drugs or supplements bought online. External testosterone can strongly suppress or completely stop the body's own sperm production. Read more about testosterone and male fertility.
The most common sign is that pregnancy does not happen despite regular unprotected sex for about a year. Sometimes there are other signals that make it worth being checked sooner:
A varicocele is a group of enlarged veins in the scrotum, usually on the left side, and it is found in around 15 % of all men. Many men with a varicocele have normal fertility, but it is more common in men with reduced sperm quality. Treatment is mainly considered when the semen analysis is abnormal and the couple is having difficulty conceiving.
Many people know that a woman's fertility decreases with age, but fewer know that male fertility is also affected over time.
The difference is that a woman's fertility declines relatively quickly as the ovarian reserve runs out, whereas the changes in men are more gradual.
Research has also shown that older men more often have sperm with reduced motility, altered shape and a higher degree of DNA damage. This can both reduce the likelihood of fertilisation and affect the chance of a healthy pregnancy.
Even though many men father children well into later life, studies show that the time to pregnancy is often longer when the man is older.
Just as female fertility is affected by lifestyle factors, sperm quality can also be affected by how we live.
An important mechanism behind this is what is known as oxidative stress. It means that the body's cells are exposed to an excess of free radicals, which can damage the sperm's DNA, among other things, and impair their function.
Lifestyle choices that reduce oxidative stress can therefore contribute to better sperm quality, and the effect shows in a semen analysis after two to three months at the earliest. Read more about lifestyle and fertility.
Smoking and snus have been clearly linked to poorer sperm quality. Nicotine affects blood circulation and hormone balance and increases oxidative stress in the body, which can damage sperm.
Research does not fully agree on exactly how much alcohol harms fertility. However, there is evidence that a high alcohol intake can impair sperm production and sperm quality.
Being overweight, particularly around the waist, can affect the hormone system and lead to lower testosterone levels. As testosterone is essential for sperm production, this can reduce fertility.
A balanced diet can contribute to better sperm quality. Nutrients such as zinc, folic acid and vitamin C have long been of interest in fertility research.
In general, a diet rich in the following is recommended:
At the same time, a high intake of ultra-processed food, sugar and large amounts of saturated fat can harm the body's health.
Antioxidant supplements such as zinc, selenium, folic acid and Q10 are often marketed to men who want to become fathers. Research has not shown for certain that they increase the chance of pregnancy, and a varied diet is the foundation. Avoid products that contain testosterone or anabolic steroids.
Regular physical activity can have positive effects on both hormone balance and sperm quality.
At the same time, both physical inactivity and very hard overtraining can harm fertility. For most men, regular moderate exercise is the best option.
The testicles sit outside the body because sperm production works best at a temperature slightly lower than body temperature.
Prolonged heat exposure can harm sperm production. It can therefore be wise to avoid situations that mean a lot of heat around the testicles for long periods.
Examples include:
There is an old myth that men should "save themselves" for the fertile days to increase the chance of pregnancy.
Research suggests the opposite.
Long periods without ejaculation can mean that a larger share of sperm become less motile and have more DNA damage. Regular ejaculation, through sex or masturbation, seems to be better for sperm quality.
For couples trying to conceive, regular sex is usually recommended, especially around the woman's ovulation.
The most important test is a semen analysis, in which a semen sample is examined under a microscope. You provide the sample by masturbation in a private room at the clinic after 1–2 days without ejaculation, and the result is usually ready the same day.
We use the WHO reference values. They are lower reference limits, and the sample is considered normal if:
An abnormal sample does not have to mean infertility, and the values vary from one sample to the next. That is why the results are always interpreted as a whole, often together with hormone tests such as FSH, LH and testosterone, and a repeat sample if needed.
Home sperm tests give a rough idea of how many sperm the sample contains. They say nothing reliable about movement and shape, so a normal home test does not rule out reduced fertility. A semen analysis at a clinic gives the full picture.
Get checked if you have been trying to conceive for about a year without success, or sooner if your partner is over 35 or you have any of the risk factors above. Both partners are assessed, because the cause can lie with one, the other or both. Read more about fertility treatment for couples.
Treatment depends on the cause. Sometimes lifestyle changes, stopping testosterone or treating a hormone imbalance is enough for sperm quality to improve.
If there are few sperm or they move poorly, IVF with ICSI is used, in which a single sperm is injected into each mature egg.
If there are no sperm in the semen, sperm can sometimes be retrieved directly from the testicle with a minor surgical procedure, TESA. If no sperm can be retrieved, treatment with donor sperm may be an option.
Before cancer treatment or other treatment that may harm fertility, you can freeze sperm for the future.
Many men only discover possible fertility problems when a pregnancy does not happen. A fertility assessment can examine sperm quality, hormone balance and other factors that affect fertility.
At Ovumia we offer fertility assessments for both women and men. Through modern analyses and individual advice, we help you better understand your fertility and the options available if you are planning to start a family.
Understanding male fertility is not only about sperm. It is about understanding how health, lifestyle, hormones and reproductive function work together to create the best conditions for a future pregnancy.
Would you like to know where you stand? Get in touch through our contact form to book a semen analysis, and see prices for semen analysis and fertility assessment.
Here we answer the questions about male fertility and sperm quality that we are asked most often.
The best way to get a picture of your fertility is a semen analysis, because most men with reduced fertility have no symptoms. If you have been trying to conceive for about a year without success, both partners should have a fertility assessment.
Stop smoking and using snus, cut down on alcohol, aim for a healthy weight, eat a varied diet, exercise moderately and avoid prolonged heat around the testicles. Avoid testosterone and anabolic steroids. The effect shows in a semen analysis after two to three months at the earliest.
Usually there are no visible signs, and the look of the semen says little about sperm quality. A semen analysis is what shows the number, movement and shape of the sperm. Problems with erection or ejaculation and changes in the testicles are reasons to see a doctor.
A diet rich in fruit, vegetables, whole grains, fish, nuts and healthy fats is good for sperm quality. Ultra-processed food, a lot of sugar and a lot of saturated fat should be limited.
Daily ejaculation does not usually harm sperm quality, and regular ejaculation, a few times a week or more, seems to be better for sperm quality than long breaks. Before a semen analysis, 1–2 days without ejaculation is recommended.
Sperm quality is usually at its best before the age of 35 to 40 and then declines gradually. Men make sperm throughout life, but with age the sperm more often move less well and have more DNA damage, and the time to pregnancy gets longer.
Yes. Cannabis, anabolic steroids and testosterone taken from outside the body can impair sperm production, and anabolic steroids and testosterone can even stop it completely. Some medicines can also have an effect, so talk to your doctor if you are unsure.
Infertility affects more than 20 % of couples of reproductive age. Male factors contribute to around half of cases, either alone or together with factors in the woman.
Yes, often. If there are few sperm or they move poorly, IVF with ICSI is used, where one sperm per egg is enough. If there are no sperm in the semen, they can sometimes be retrieved directly from the testicle.
Medically reviewed by Åsa Rylander, specialist in obstetrics and gynaecology, Ovumia Sweden · Last updated 2026-10-01.
