Does TRT affect fertility?
Yes. TRT fertility effects are well documented: it lowers sperm production, often to very low levels or to zero. One medical review is titled “Testosterone Is a Contraceptive and Should Not Be Used in Men Who Desire Fertility.”
The Endocrine Society, a major US group of hormone doctors, recommends against starting testosterone if you plan to have children soon. The good news is that sperm production came back after stopping in most men studied. The catch is that recovery takes months, varies a lot, and isn’t guaranteed.
That’s why the talk about children belongs before you start TRT, not after. This guide explains what the research shows. It isn’t advice about your own treatment or fertility, and a prescriber or fertility specialist who knows your history is the right person for that.
How does testosterone therapy lower sperm production?
Your brain tells your testes to make sperm using two hormones. LH (luteinizing hormone) tells the testes to make testosterone. FSH (follicle-stimulating hormone) helps drive sperm production.
When testosterone comes from outside your body, your brain senses plenty of it and turns those two signals down. The DEPO-Testosterone label describes this effect on LH, and at high levels on FSH too. Without LH, your testes make far less of their own testosterone.
Making sperm takes a very high level of testosterone inside the testes, much higher than in your blood. In one study, healthy men got weekly testosterone shots for three weeks. Their LH and FSH fell to 5% and 3% of where they started.
In the group that did not get hCG (a hormone covered below), testosterone inside the testes fell by 94%.
So your blood testosterone can look healthy on treatment while sperm production falls. Our page on LH and FSH explains these hormones further.
Why doesn’t a normal testosterone level protect fertility?
Because the testosterone that matters for sperm is the testosterone inside the testes, and a blood test can’t see it. In healthy men, the level inside the testes is far higher than in the blood. In one study, blood testosterone was only about 1.2% of the level inside the testes.
Another study found that testosterone inside the testes rose and fell closely with LH in the blood.
On TRT, the testosterone in your blood comes mostly from treatment, while LH and your testes’ own production fall. So a lab report can show a healthy level while sperm production shuts down.
“My levels are fine” doesn’t answer the fertility question. A semen analysis, which counts and checks your sperm, does.
How likely is TRT to lower your sperm count?
Very likely, though the numbers depend on who was studied. The clearest data come from trials that tested testosterone as male birth control in healthy, fertile volunteers.
| Study | Who | What happened |
|---|---|---|
| WHO 1990 | 271 healthy men, weekly injections | 65% had no sperm in their semen within 6 months |
| WHO 1996 | 399 healthy men, weekly injections | Most reached very low counts; some never suppressed fully |
| Samplaski 2014 | 59 infertility-clinic patients who had taken testosterone | 88.4% had no sperm while on it |
| Hsieh 2013 | Background statement in a paper on men on TRT | Azoospermia in about 40% of patients |
Azoospermia means no sperm at all in the semen. Product labels carry the same warning. The Xyosted label says some men on testosterone have reduced fertility and the effect “may be irreversible.” The DEPO-Testosterone label lists shrinking testicles (testicular atrophy), subfertility and infertility among possible effects.
How fast does sperm count drop on TRT?
Over weeks to months, not days. Researchers pooled nearly 14,000 semen samples from two WHO studies.
They estimated that sperm output halves about every 5.5 weeks and reaches 1 million per mL after about 13 weeks. In the 1990 WHO study, the average time to reach zero was 120 days.
Those studies used weekly shots in healthy young men, so your own pattern may differ. The point for planning is simple. There is no safe window early in treatment to rely on, and the effect builds quietly without symptoms.
Does TRT shrink the testicles?
It can. The DEPO-Testosterone label lists testicular atrophy, along with subfertility and infertility, among problems reported in men on testosterone. The label doesn’t say how often it happens.
A change in testicle size isn’t a fertility test. Some men notice it and some don’t.
If you notice a change in size, a new lump or pain, tell your prescriber. A new lump always needs to be checked.
Is TRT a reliable form of birth control?
No. Testosterone lowers sperm counts, but not reliably enough to prevent pregnancy.
In the 1996 WHO study, four pregnancies happened over 49.5 person-years in men whose counts were very low but not zero. None happened in men with no sperm at all.
Some men’s counts never fell far enough, and some “escaped” suppression later.
Those men had regular semen tests under supervision, and men on everyday TRT usually don’t. If you don’t want a pregnancy, use contraception. If you do, talk to your prescriber rather than counting on TRT either way.
Does the type of testosterone matter for fertility?
Possibly, but the evidence is thin. The ASRM, the main US fertility society, says it’s “generally believed” that injections and pellets are more likely to cause infertility than gels. It adds that any form of testosterone can disrupt sperm production.
In contraception studies, shorter-acting testosterone was linked to somewhat faster recovery, though the effect was small. The labels we checked all carry a warning about sperm production.
Which form you use is your prescriber’s call. Our testosterone level calculator shows how long different injectable forms stay in the blood.
How long does it take for sperm to come back after stopping TRT?
Usually months, sometimes longer. The best numbers come from an analysis of 30 hormonal contraception studies with 1,549 healthy men aged 18 to 51. It tracked how many men got back to 20 million sperm per mL, a level linked with fertility.
- Within 6 months: 67% of men.
- Within 12 months: 90%.
- Within 16 months: 96%.
- Within 24 months: 100%.
The typical time was 3.4 months. Recovery was faster in older men, with shorter treatment and with shorter-acting testosterone.
An earlier WHO study found a typical time of 3.7 months to reach 20 million per mL. Getting back to each man’s own starting level took 6.7 months.
Men on real-world TRT may not match these numbers. The AUA (American Urological Association) guideline warns that the contraception results may not apply to men with low testosterone.
It says there are no high-quality reports of sperm recovery in men with low testosterone who used testosterone. It also says some infertile men may never recover sperm production, and that the time course is highly variable.
In infertility-clinic patients who had taken testosterone, about two thirds recovered within 6 months of stopping.
In another clinic study, 66 men stopped testosterone and also had hCG and SERM treatment for infertility. Older age and longer testosterone use were linked with slower recovery. One review concludes that many men recover if given time, but some don’t.
Stopping also brings back the symptoms of low testosterone while your own production restarts. Don’t stop on your own. Plan it with your prescriber.
What do guidelines say about TRT if you want children?
The major US guidelines agree on the basic message.
- Endocrine Society (2018): recommends against starting testosterone therapy in men planning to have children in the near term.
- AUA (2018): says testosterone should not be prescribed to men who are trying to conceive now. It also says to discuss the long-term effect on sperm production with men who want children later.
- AUA and ASRM male infertility guideline (2020, amended 2024): says that for a man interested in current or future fertility, clinicians should not prescribe testosterone therapy.
- ASRM patient guidance: men who want biological children should avoid testosterone or consider freezing sperm first.
None of this means you can never have treatment. It means fertility is a deliberate decision, made with your prescriber, and sometimes with a fertility specialist, before you start.
What about hCG with TRT?
hCG (human chorionic gonadotropin) is a hormone that acts like LH on the testes. Researchers have studied it alongside testosterone to see whether it keeps sperm production going. This is what the studies show, and it is not a recommendation.
- In healthy men whose LH and FSH were suppressed with testosterone for three weeks, small amounts of hCG kept testosterone inside the testes in the normal range. That study measured hormones, not sperm or pregnancies.
- In a look back at 26 men on TRT plus hCG, none developed azoospermia over about six months, and 9 contributed to a pregnancy. The study was small and had no comparison group.
Guidelines don’t recommend this combination. The AUA and ASRM infertility guideline says some studies have shown preserved sperm production when hCG is added to testosterone, with or without other drugs. But it says the research is too limited to recommend the approach.
The AUA’s 2018 testosterone guideline says clinicians may use other options instead. These are aromatase inhibitors, hCG, SERMs or a mix, for men with testosterone deficiency who want to keep their fertility. It is a conditional recommendation based on limited evidence.
The ASRM fact sheet adds that other off-label medicines exist that raise a man’s own testosterone. They need hormone tests and semen analyses, and a reproductive specialist should guide the choice. Whether any option like this suits you is a question for your prescriber or a fertility specialist.
Does low testosterone itself cause infertility?
Not directly. The ASRM says that low testosterone “does not cause infertility.” Sperm production depends on testosterone inside the testes and on FSH, not on the blood level alone.
But the two can travel together. In a Swedish study of national records, men who had children through ICSI, an IVF technique, were more likely than men who conceived on their own to be prescribed testosterone in the following years. The authors conclude that routine hormone checks for men seeking fertility treatment are warranted.
Problems with the testes or the pituitary gland can lower both testosterone and sperm production. That is one reason to find the cause of low testosterone before treating it. Your doctor may check LH and FSH to help tell these causes apart.
What should you ask before starting TRT if you might want children?
Bring these questions to your prescriber, ideally with your partner.
- Timing: If we might want children in the next few years, should I wait, or are there other options?
- Baseline: Should I have a semen analysis before starting? The Endocrine Society says one may be done to see whether contraception is needed. It also gives us a comparison point.
- Sperm freezing: Is banking sperm worth considering for me, and where would I do it?
- Specialist: Would seeing a urologist or fertility specialist first be useful?
- Stopping later: If we decide to try for a pregnancy, what would the plan look like?
Our guide to questions to ask your TRT doctor has a printable question list.
If you do start, keep a simple record of your treatment, labs and symptoms. If plans change later, a clear history of what you took and when makes the fertility talk easier. The blood test timing planner helps you plan lab draws so results are comparable.