Sauna, hot tubs and sperm count: what the heat research shows
A study put healthy men through a normal sauna routine and measured what happened to their sperm. The effect was clear, and so was the recovery six months later, which is the part that gets left out of the scary version.
Short answer: In a 2013 Human Reproduction study, 10 healthy men who used a Finnish sauna twice a week for three months, 15 minutes at 80 to 90°C, had a strong drop in sperm count and motility with no significant change in sex hormones, and every change had fully reversed six months after they stopped. Hot tubs show the same pattern: in a 2007 study of infertile men, about half improved markedly after giving up hot tubs and hot baths. It matters if you are trying to conceive and very little otherwise.
Testicles sit outside the body for a reason: sperm production works best a few degrees below core temperature. Anything that heats them reliably reduces output, and a sauna heats them.
That much is uncontroversial physiology. What makes the sauna question answerable is that someone measured it properly, with a normal sauna routine rather than an artificial heating device, and then followed the men afterwards to see what happened.
The result has two halves, and the second half is the one usually dropped. The effect is real, and it reverses.
What did the study find?
A clear drop, and a full recovery.
The reference is Garolla and colleagues in Human Reproduction in 2013, which put healthy men through regular Finnish sauna sessions and tracked semen parameters through exposure and afterwards.
The protocol was an ordinary habit: 10 men with normal semen results used a Finnish sauna twice a week for three months, each session 15 minutes at 80 to 90°C. At the end, the study found a strong impairment of sperm count and motility, with no significant change in sex hormones.
The changes went deeper than counts. The share of sperm with normal chromatin packaging and normal mitochondrial function fell too, and genes involved in the response to heat stress and low oxygen were switched up.
Then it recovered. The researchers checked again three and six months after the men stopped, and at six months all of these effects were completely reversed. The caveat is the one the authors give: every volunteer started with normal semen, so the study cannot say how men with low counts respond, and it measured semen rather than pregnancies.
Hot tubs and sperm count
The hot tub evidence comes from men already being treated for infertility. In a 2007 study by Shefi and colleagues in the International Brazilian Journal of Urology, 11 infertile men who regularly used hot tubs, Jacuzzis or hot baths stopped, and their semen was tested again.
Five of the 11, 45%, responded strongly: their total motile sperm count rose by an average of 491%, mostly because motility climbed from 12% to 34%. The other six did not respond, and they had smoked far more, which the authors suggest as one explanation.
It is a small study without a control group, so it shows that stopping wet heat can help, not how often. Its conclusion matches the sauna study’s: the effect of heat on semen “may be reversible in some infertile men.”
How much heat matters?
Duration and regularity more than a single visit.
The clearest effect in the research came from a sustained habit over weeks. A single session is not nothing, though: in a small 1984 study, one 20-minute sauna at 85°C lowered sperm numbers within a week, and they “slowly returned to normal in 5 wk.” No study has shown that an occasional sauna makes pregnancy less likely, so for most people an occasional visit is not a fertility decision; if you are actively trying, it is one more reason to pause.
Regular, frequent, prolonged heat is the pattern that showed an effect: two sessions a week for three months in the sauna study, and habitual hot tubs or hot baths in the infertility study. Hot tubs also keep the whole lower body immersed for as long as you stay in, which makes long soaks easy. Our guide on how often to use a sauna covers the cadence question generally.
Sauna and male fertility at a glance
| Effect on sperm parameters | |
|---|---|
| One sauna session | Sperm numbers fell within a week and returned to normal in 5 weeks, in one small 1984 study |
| Regular sauna habit over weeks | Measurable drop in count and motility |
| Habitual hot tubs or hot baths | 5 of 11 infertile men improved strongly after stopping (2007 study) |
| Recovery after stopping | Completely reversed 6 months after stopping (2013 study) |
| If not trying to conceive | Not a practical concern |
| If actively trying | Worth pausing the heat habit |
| Effect on testosterone | Different question, not the same as sperm |
Does this mean heat lowers testosterone?
No, and the two get conflated constantly.
Sperm production and testosterone production happen in different cells in the testes and respond differently. A drop in sperm count is not evidence of a drop in testosterone, and the studies measuring semen parameters mostly did not find the hormonal collapse people assume.
In the 2013 sauna study, sex hormones did not change significantly even while sperm count and motility fell. The internet version of this topic merges the two into a single claim that heat ruins male hormones, and it does not follow from the evidence.
The mirror-image myth, that cold exposure raises testosterone, is equally unsupported. Our guide on whether cold exposure raises testosterone goes through that evidence.
So who should actually change anything?
Men actively trying to conceive, and few others.
If you and your partner are trying, pausing regular sauna and hot tub use is cheap and reversible. In the sauna study, recovery was measured as complete six months after stopping, so stopping several months ahead is more useful than stopping the week before.
If you have had a semen analysis showing low count or motility, mention your heat habits to your doctor, because it is one of the more easily removed contributors.
If neither applies, this is not a reason to give up the sauna. The cardiovascular associations with regular sauna use are the better-established part of this literature, and they do not disappear because of a reversible effect on fertility. Our guides on sauna and the heart and what the sauna evidence supports cover that side.
What about cold plunging?
No good evidence either way, and no, it does not fix this.
There is a popular idea that cold exposure boosts fertility or counteracts heat exposure. There is no meaningful research supporting it, and cold plunging after a sauna does not undo the exposure your testes just had.
Cold has its own well-studied effects, mostly on soreness and alertness, and its own honest limits. Our guide on what the cold plunge evidence shows covers them.
If you are pausing heat for fertility reasons, pause the heat. Adding cold is not a workaround, and it does not buy you the sauna back.
FAQ: sauna and male fertility
Does a sauna lower sperm count? Regular use can. In a 2013 study, two 15-minute sessions a week at 80 to 90°C for three months strongly reduced sperm count and motility in healthy men, and the changes had completely reversed six months after they stopped.
Do hot tubs lower sperm count? Habitual wet heat is linked with lower semen quality. In a 2007 study of 11 infertile men who used hot tubs or hot baths, five improved strongly after stopping, with total motile sperm count up by an average of 491%.
How long should I stop before trying to conceive? In the 2013 study, every change had reversed six months after stopping. The study did not pin down when recovery began, so stopping several months ahead is the cautious reading, and your doctor can advise on your own timing.
Is an infrared sauna safer for fertility? Not established. The relevant variable is how hot the tissue gets and for how long, not which technology produced the heat. Our infrared vs traditional comparison covers the differences.
Are hot tubs worse than saunas? We cannot say. We found no study that compared them directly: the clearest dose study used a sauna, and the hot tub study had 11 men and no control group. Our sauna vs hot tub comparison sets out what each found.
Is the effect permanent? The evidence points to recovery after stopping: in the sauna study, every measured change had reversed six months later, and about half of the infertile men in the hot tub study improved after giving it up.
The bottom line on sauna and male fertility
Regular sauna exposure strongly reduced sperm count and motility in healthy men, with molecular changes alongside, and every change had reversed six months after stopping. Habitual hot tubs show the same pattern in infertile men. Both halves are part of the finding.
If you are actively trying to conceive, pausing regular heat several months ahead is a cheap and reversible thing to do. If you are not, an occasional sauna is not a fertility decision, and it does not lower your testosterone either.
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