How to increase male fertility: 10 factors you control

To increase male fertility you mostly stop doing things, rather than start taking something. Search for how to increase male fertility and almost every result is about supplements. That is exactly where the evidence is thinnest.

In 2020 the largest trial ever run on this question was published. More than 2,300 men took folic acid and zinc or a placebo. Effect on semen quality: none. Effect on live births: none (Schisterman and colleagues, 2020).

Below are ten factors, ordered by how much evidence sits behind them. We sell blood tests, so each factor also states which value you can measure, and where a blood test tells you nothing at all.

What you can change and what you can measure

Six of the ten factors below have a blood value directly underneath them. Four do not. That honest split is more useful than a list where everything looks equally measurable.

1. Stop smoking

This is the best supported factor on the list. A meta-analysis of 20 studies covering 5,865 men found lower sperm count, lower motility and worse morphology in smokers (Sharma and colleagues, 2016). The gap was larger in moderate and heavy smokers than in light smokers.

The difference works out at roughly 9.7 million sperm per millilitre. That is not a marginal number.

2. Cut back on alcohol

Heavy drinking is associated with lower semen volume and poorer semen quality. At moderate intake the picture is messier and less convincing. Honestly, this is a factor where the evidence is weaker than the confidence with which it is usually written about.

What you can measure: your liver values GGT and ALT show what your drinking pattern does to your liver. That mirrors your intake, not your semen quality.

3. Deal with belly fat

Fat tissue converts testosterone into estradiol. More belly fat therefore often means lower testosterone and higher estradiol, and that combination dampens the signalling that drives sperm production. It is one of the few factors here whose effect shows up directly in your blood.

Measurable: testosterone, SHBG and estradiol. What actually works to shift it is covered in losing belly fat as a man.

4. Keep your scrotum cool

Your testicles sit outside your body because sperm production wants to run a few degrees below body temperature. In research on testicular heat stress, a one degree rise in median daytime scrotal temperature goes together with roughly 40% lower sperm concentration (Robinson and colleagues, 2023).

In practice: long uninterrupted sitting, a laptop on your lap, and frequent sauna use. The effect is not immediate. It surfaces after one to two weeks and peaks around four to five weeks later.

5. Check your zinc status, but do not supplement blindly

This is where almost every other page gets it wrong. Zinc sits in virtually every male fertility supplement. In the FAZST trial, 2,370 men took folic acid with zinc or a placebo, double blind. There was no difference in semen quality and no difference in live births (Schisterman and colleagues, 2020).

Finding and correcting a deficiency is not the same as supplementing preventively. The first is reasonable, the second is not demonstrated. More nuance in zinc and testosterone.

6. Check your vitamin D

A low vitamin D status is associated in observational research with lower sperm motility. Note the word associated. That is not a proven cause, and the trials testing supplementation are smaller and less consistent than the marketing suggests.

It is a value that is often low in the Netherlands and easy to measure. See vitamin D deficiency in men.

7. Check your thyroid

Both an underactive and an overactive thyroid can disturb sperm production, and both produce symptoms you would easily attribute to something else. It is a cheap thing to rule out: TSH and free T4 usually suffice to see whether anything is going on.

How your thyroid and your male hormones interact is covered in thyroid and testosterone.

8. Stop anabolic steroids or exogenous testosterone

This is the heaviest factor on the list and simultaneously the one you will not find on any other fertility page. Testosterone from outside suppresses your LH and FSH through feedback, and those two hormones are precisely what drives sperm production (Fusco and colleagues, 2021).

The consequence is not subtle. In men on testosterone, azoospermia, meaning no measurable sperm, is a known and expected effect. In this respect testosterone works as a contraceptive.

Here is an example of why testosterone alone tells you nothing here. Two men both have a total testosterone of 22 nmol/l. Comfortably mid-range. The first produces it himself: his LH is 4.5 and his FSH 3.8, both normal. The second has used testosterone gel for eight months: his LH and FSH sit below the detection limit, and his semen analysis shows no sperm at all.

Same testosterone, opposite fertility. The difference lives in LH and FSH, and those are exactly the two values a standard testosterone test often leaves out.

Recovery after stopping often happens, but not reliably in full and not on a predictable timeline. If you want children, discuss this with a doctor before you start. See Sustanon and your blood values and clomiphene in men.

9. Get enough sleep

One week of five hours of sleep per night lowered daytime testosterone by 10 to 15% in healthy young men (Leproult and Van Cauter, 2011). That was one week. Not a year.

Testosterone is not the same thing as fertility, so do not talk yourself up or down on this single number. But the signalling that drives sperm production runs through the same system. See poor sleep and your testosterone.

10. Get a semen analysis as a baseline

This is the most sober step of all. All nine points above are estimates as long as you do not know where you started. A semen analysis gives you count, motility and morphology, and therefore something to measure change against.

How to read that result is covered in semen analysis values. If a varicose vein in the scrotum might be in play, also read varicocele and fertility.

What a blood test cannot do here

A blood test does not measure your semen quality. Full stop. It shows hormones and deficiencies that can influence sperm production, which is useful, but it is an indirect route. If you want to know how your semen is doing, a semen analysis is the direct one.

We sell blood tests, so feel free to read that paragraph twice.

When should you take this to a doctor?

The Dutch guidance from Thuisarts.nl is to make contact after a year of unprotected trying without a pregnancy. If there are reasons to go sooner, such as an undescended testicle in the past, groin surgery, or a scrotum that hurts, do not wait.

The causes a doctor checks are listed in male infertility causes. A broader introduction to the topic is in male fertility.

My own conclusion after reading this research: the cheapest gains are in stopping, not in taking. Smoking, alcohol, heat and exogenous testosterone cost you nothing to address, and they carry more evidence than the entire supplement shelf combined.

References

• Schisterman EF, Sjaarda LA, Clemons T, et al. Effect of folic acid and zinc supplementation in men on semen quality and live birth among couples undergoing infertility treatment: a randomized clinical trial. JAMA. 2020. PMID 31910279
• Sharma R, Harlev A, Agarwal A, Esteves SC. Cigarette smoking and semen quality: a new meta-analysis examining the effect of the 2010 World Health Organization laboratory methods for the examination of human semen. European Urology. 2016. PMID 27113031
• Fusco F, Verze P, Capece M, Napolitano L. Suppression of spermatogenesis by exogenous testosterone. Current Pharmaceutical Design. 2021. PMID 33292112
• Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011. PMID 21632481
• Robinson RS, et al. Testicular heat stress, a historical perspective and two postulates for why male germ cells are heat sensitive. Biological Reviews. 2023.
• Thuisarts.nl. We want to get pregnant. 2025. thuisarts.nl
• RIVM. Figures on lifestyle, smoking and health. 2025. rivm.nl

Every blood test result includes a professional assessment by a BIG-registered doctor. Discuss your results with your doctor before making treatment decisions.