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Natural Variation in Semen Quality


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When testing semen quality, it is important to know that one test is not always enough. This is because of the natural variation in the semen quality, including parameters such as volumeconcentrationmotility, and morphological features.

Therefore, just because one test is suboptimal, the next one could still be OK! This is also why testing more than once is an important part of the testing guide provided by the World Health Organization (WHO) – especially if your first test is low.

How much variation is natural in semen quality?

It is difficult to predict how much variation men individually have in semen quality over time. Some men are quite stable over time, while others have large variations. The below graphs show the variation in semen quality of five men who were tested numerous times at the same clinic over a period of 540 days [1]. In the graphs, the left side represents the total number of sperm cells in the ejaculate. The right side represents the concentration (million sperm cells per ml of semen).

Sperm quality variation

The graphs illustrate that even though the testing is highly controlled in a professional laboratory, there will be individual variation in semen parameters over time. We’ll start by looking at the graphs for man #4. His total number of sperm cells rose from about 200 million sperm cells in his ejaculate in test 3 to almost 600 million in test 4. For man #2, his concentration went from below 20 million sperm cells/ml of semen in test 4, to more than 200 million sperm cells/ml of semen in test 5. This also means that the normal variation can be quite substantial.

It is because of this variability that we strongly recommend our users analyse at least two ejaculates to determine their semen quality.


What causes natural variation in semen quality and how can you compare over time?

Sperm cells differ from the other cells in the body with their unique shape and movement patterns. Importantly, sperm production takes about three months.  During this process, several factors can affect the amount and the quality of the sperm cells produced.

What can affect a semen analysis result

In our article How to collect a semen sample for home sperm testing we describe some of the external factors that are important to consider when testing semen quality over time. Firstly, the length of abstinence before testing seems to affect the quality. This is also why you should be consistent in the collection. Secondly, every drop counts so it is important to collect all liquid ejaculated. In terms of variation in motility, the time before testing may also affect this.  It is important to test within 60 minutes of collecting the sample. This way you can be sure that the sperm cells do not stop their movement.

Furthermore, in terms of collection, some studies show that the quality of semen parameters varies depending on how the ejaculation is produced. Some studies show that ejaculates produced by masturbation and collected in a clinic can be of lower quality than those produced at home during intercourse with partner. This difference may reflect a possible difference in sexual arousal [2][3].



Most important factors that can affect the results of a sperm analysis:

  • Collection of the first drops of the semen sample. During ejaculation, the first drops (or fraction) of the sample is often very rich in sperm cells. It is therefore important to collect this portion as it has more influence on the overall sperm quality than the rest of the sample.
  • Period of sexual abstinence. How long the man has abstained to providing a semen sample correlates with the results of semen analysis. Too long abstinence can result in low concentration and motility. We recommend an abstinence of around 48 hours before doing a test to produce the optimal conditions for the analysis.
  • Frequency of ejaculation up to the day of sperm analysis. Daily sexual activity increases sperm quality in men minimizing DNA damage in the sperm. Shorter storage of maturated sperm cells means less damage may accumulate in sperm DNA [4].

External factors

Besides from this, illnesses that increase the body temperature (like for example an influenza or COVID-19) have also been shown to decrease sperm quality. This means that an incident of fever can be negatively affect the production of sperm in the testicles. It usually take a number of weeks before normalizing again.

As we describe in other articles on our blog, lifestyle choices can also impact sperm quality. Studies show that adopting new and healthier habits can boost semen quality. This includes semen volume, sperm concentration, sperm motility, as well as lowering sperm DNA-damage. It takes a long time to produce sperm cells. Therefore, changes in sperm quality from lifestyle adjustments occur several months later.

All the above factors can contribute to a variation in sperm numbers over time within the same individual. This is also shown in other studies where semen samples collected from healthy young men have shown differences in sperm quality over time [5].


Now what?

To sum up, firstly, it is important that you test your semen quality at least twice, and secondly, if you want to compare semen quality over time, you should stay consistent and follow our tips in How to collect a semen sample for home sperm testing.



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Wearing tight pants and underwear

Studies show that men who wear looser underwear have higher sperm concentration and total sperm count compared to men who wear tighter underwear. So, lose the tight clothes and wear something loose to give your testicles some air.

CONCLUSION: learn more about how heat can affect sperm quality here.


Besides higher mortality rate and various diseases, stress is associated with low sperm quality. Stress is known to be associated with lower testosterone levels and oxidative stress with both playing an essential role in producing and maintaining healthy sperm cells.

CONCLUSION: If you feel stressed, we recommend you get some help so you can have a balanced mental health. For a stress management guide, download the ExSeed app for free and start your personalized action plan today.

Physical activity

Scientific studies show that men who are physically active have better semen parameters than men who are inactive. Fertility specialists also state that regular physical activity has beneficial impact on sperm fertility parameters and such a lifestyle can enhance the fertility status of men.

Prioritizing exercise can help improve your overall health and result in healthy, fast swimming sperm cells that have good chances of fertilizing an egg.

CONCLUSION: Try incorporating exercise in your weekly schedule to you ensure exercising at least twice weekly. We recommend a combination of cardio training and strength exercise. Read more about exercise and male fertility on our blog.


Fast Food
Processed foods damage the health of sperm-producing cells and cause oxidative stress, which lead to poorer sperm quality. Heavy consumption of junk food (every week) can increase the likelihood of infertility since men who consume vast amounts of unhealthy food are at risk of having poor sperm quality. Besides harming your fertility, junk food enlarges your waistline, harms your cardiovascular system, kidneys, and more.

Eating more fruit and vegetables can increase your sperm concentration and motility. It’s important that you consume a healthy diet filled with antioxidants and that you eat vegetables every day. Foods such as apricots and red bell peppers are high in vitamin A, which improves male fertility by nurturing healthier sperm. Men who are deficient in this vitamin tend to have slow and sluggish sperm.

Sugary snacks/beverages: several times a week Excessive consumption of high sugar items can lead to oxidative stress, which negatively impacts testosterone levels and sperm motility. Sugary snacks and beverages are also highly associated with obesity and low fertility.
CONCLUSION: To boost sperm quality, stay away from fast food, processed food, and sugary snacks or beverages. You need to implement a healthy prudent diet filled with necessary superfoods needed for good sperm production. Check out our guide to Male Fertility Superfoods. For personalized guidance and support on how you can start improving your sperm health, check out the Bootcamp.


Direct heat can inhibit optimal sperm production and cause Sperm DNA damage. Sperm cells like environments that are a couple of degrees lower than body temperature. Avoid overheating from warm blankets, seat warmers, heat from your laptop, hot showers, and saunas.

Cigarette smoking

The exposure to tobacco smoke has significant negative effects on semen quality. The damage of cigarettes and nicotine of course depends on how many cigarettes you smoke per day and for how long, but even low usage (up to 10 cigarettes / day) can inhibit healthy sperm production.  

CONCLUSION: Stay as far away from cigarette smoking as possible if you care about your general health and your fertility. Read more here.

Cell phone

When you have your cell phone in your front pocket, your testicles are exposed to electromagnetic radiation, which studies have shown to damage the sperm cells. Put your phone in the back pocket of your pants or in your jacket pocket.


There is a clear association between obesity and reduced sperm quality. At least part of the reason for this is that obese men may have abnormal reproductive hormonal profiles, which can impair sperm production and lead to infertility. 

A BMI higher than 30 can lead to several processes in the body (overheating, increase in oxidative stress in the testes, sperm DNA damage, erectile dysfunction) that can have a negative impact on male fertility. This can result in problems when trying to conceive.  

CONCLUSION: BMI is one of the risk factors that influence semen quality and, for example, sperm motility.  


A beer or glass of wine now and then do not really harm sperm quality. But excess alcohol drinking (more than 20 units per week) can reduce the production of normally formed sperm needed for a successful pregnancy.

CONCLUSION: If you want to stay safe, stay under 14 units of alcohol per week. For more information on how alcohol can affect male fertility, take a look at our blog: “Alcohol and Sperm Quality”.


Studies show that women younger than 35 and men younger than 40 have a better chance of getting pregnant. Men can produce sperm cells almost through their entire life, but the sperm cell DNA is more fragile and prone to damage after the age of 40.

As men age, their testes tend to get smaller and softer resulting in a decline in sperm quality and production. These changes are partly because of an age-related decrease in testosterone level, which plays a very important role in sperm

production. Higher male age (>40 years) is not only associated with a decline in sperm production but also with increased sperm DNA fragmentation and worsened morphology (shape) and motility (movement). These negative effects make the sperm cells less qualified for egg fertilization.

CONCLUSION: with an age under 40, you shouldn’t have to worry much about age as a factor in itself. However, studies have shown a slow decline after the age of 30-35 years

and if you are above 40 years of age, your sperm quality can be affected due to increased sperm DNA damage resulting in a decrease of sperm motility and concentration. Remember that you cannot evaluate the quality of a sperm sample by just looking at it – this requires a sperm analysis.