Can Mounjaro Make You Infertile?

Does the research show any link between tirzepatide and infertility?

No published data from the SURMOUNT clinical programme identifies infertility as an adverse effect of tirzepatide. Thousands of adults took part in SURMOUNT-1 alone, and the side-effect profile that emerged was dominated by gastrointestinal symptoms (nausea, loose stools, constipation, indigestion) not reproductive harm. The NHS medicines page for tirzepatide lists the known side effects and does not include infertility among them.

That said, Mounjaro is a relatively new medicine carrying a Black Triangle designation, which means the MHRA continues to collect post-marketing safety data. Long-term effects on fertility have not been studied in dedicated trials. The honest position is: no signal has appeared, but the research simply hasn't been done on that question specifically. If fertility is a concern for you, that is exactly the kind of conversation to have with a prescriber before starting.

One thing to hold alongside this: Mounjaro is not recommended during pregnancy or breastfeeding, and it is not licensed for under-18s. Anyone trying to conceive should stop treatment first and allow an appropriate washout period, discussed with their clinical team. It is also worth knowing that questions about whether Mounjaro can affect vision are covered separately, as eye-related concerns sometimes arise alongside broader safety queries about this medicine.

Could weight loss on Mounjaro actually affect fertility the other way?

This is the question our prescribers are asked more often than the infertility one, and the answer matters. Excess weight is associated with disrupted ovulation, polycystic ovary syndrome (PCOS), and altered testosterone levels in men. Losing a meaningful amount of weight can restore hormonal balance and improve reproductive function in both sexes. Some people who believed they had fertility difficulties have found those difficulties change after significant weight loss.

In practical terms, that means someone starting Mounjaro may become more fertile over the course of treatment, not less. There is a separate, detailed page on whether Mounjaro may increase fertility if you want to work through that side of the question. The key point here is not to assume treatment reduces reproductive capacity; for many people the opposite may be true, and that warrants proper contraceptive planning from day one.

The NHS England guidance on weight-management injections specifically addresses reproductive considerations for patients on GLP-1 medicines, and is worth reading in full.

What are the contraception precautions on Mounjaro, and why do they exist?

Mounjaro slows gastric emptying — the rate at which your stomach passes its contents into the small intestine. This is part of how it reduces appetite. The same mechanism can reduce the absorption of oral contraceptive pills, which rely on being taken up through the gut reliably each day.

Because of this, the guidance is clear: women using oral contraceptives should use a second, non-oral method of contraception (condoms are the obvious choice) for the first four weeks of treatment and for four weeks after every dose increase. The titration schedule for Mounjaro typically steps up in four-week intervals, so this is a recurring commitment throughout the dose-escalation phase. A condom in your bag alongside the pen in the fridge door is a reasonable mental note to set.

This is not a hypothetical risk invented out of caution; it reflects a real pharmacokinetic interaction. If you use a non-oral method already (the patch, an IUD, an implant, an injection) you do not need to add anything further. If you are uncertain about your current contraceptive method's interaction with tirzepatide, your prescriber or GP is the right person to ask. For anyone currently exploring the costs of treatment, context on Mounjaro pricing in the UK may also be useful.

What should you do if you are planning a pregnancy while on Mounjaro?

Stop treatment before trying to conceive, with a washout period agreed with your prescriber. Mounjaro is not recommended in pregnancy; the medicine is not licensed for use during pregnancy or breastfeeding, and the safest approach is to ensure it has cleared your system before conception. Your prescriber will advise on timing based on your dose and how long you have been on treatment.

It is also worth thinking about what happens to your weight-management plan during that window. Some of the weight lost on treatment may return when the medicine is stopped; planning for that, and having lifestyle support in place, is part of a sensible pre-conception conversation. If dizziness, bleeding changes, or other symptoms have arisen during treatment, those are also worth discussing, information on bleeding changes and on dizziness are covered in detail elsewhere.

If you have questions about how Mounjaro fits around your specific reproductive health situation, speaking with a prescriber is the only way to get an answer tailored to you. Start a free consultation with our clinical team, where a GPhC-registered Independent Prescriber reads every response personally on the same day.