Natural Variation in Semen Quality

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 volume, concentration, motility, 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).

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].

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.