Mounjaro and Fertility: What the Evidence Actually Says

Is it safe to try for a baby while taking Mounjaro?

The short answer is no. Mounjaro's prescribing information is clear: tirzepatide should be stopped before attempting to conceive. The MHRA advises using effective contraception throughout treatment and for a defined washout period afterwards. The SmPC for tirzepatide, published on the electronic Medicines Compendium, states that the medicine is not recommended during pregnancy because animal data showed adverse effects on embryo-fetal development at exposures relevant to human use. Human data in pregnancy remain very limited.

A question our prescribers hear most weeks is whether it is safe to stop Mounjaro suddenly once a pregnancy test comes back positive. The advice is to contact your prescribing team and your GP straight away. Stopping abruptly does not carry the same risks as stopping some other medicines, but your clinical team needs to know so that appropriate monitoring and support can be put in place during the pregnancy.

For broader context on what is and is not known about tirzepatide's effects in women of reproductive age, the detailed page on Mounjaro and female fertility covers the evidence in full.

Does Mounjaro affect the contraceptive pill?

Yes, and this is one of the most practically important points for any woman on oral contraception. Because tirzepatide slows the rate at which food and medicine leave the stomach, it can reduce absorption of the oral contraceptive pill. NHS England's guidance on weight-management injections is explicit: women on the pill should use an additional barrier method for the first four weeks of Mounjaro treatment and for four weeks after each dose increase.

This matters both for contraceptive reliability and for treatment safety. Starting Mounjaro without addressing the pill interaction creates two problems at once: an increased pregnancy risk, and exposure of any unintended pregnancy to a medicine that is not recommended in that situation. Transdermal forms of contraception (patches, for example) and non-oral methods are not affected by gastric-emptying changes in the same way. If you are unsure which contraceptive method suits you during treatment, your GP or sexual health clinic can advise.

The interaction picture is different for semaglutide; our explainer on how tirzepatide affects fertility compares the two where the evidence allows.

Can Mounjaro improve fertility indirectly through weight loss?

This is where the picture gets more nuanced. Excess weight is associated with hormonal disruption that can impair ovulation. Conditions such as polycystic ovary syndrome (PCOS) are closely linked to insulin resistance, and significant weight loss often leads to improved cycle regularity and, in some cases, restored ovulation. Clinical trials for tirzepatide, including SURMOUNT-1, published in the New England Journal of Medicine, documented substantial average weight reductions, which for some patients with weight-related reproductive conditions could theoretically translate to improved hormonal function.

The critical caveat is timing. Fertility may improve before a planned washout period is complete. This is exactly why robust contraception throughout treatment is not optional for women who do not want to become pregnant during this period. It is also why anyone who is actively trying to conceive should not be on Mounjaro at the same time. These are conversations for a GP or reproductive specialist, not something to manage by adjusting treatment without clinical input.

Research into GLP-1 receptor agonists and direct fertility outcomes in humans is ongoing. The current state of the evidence on Mounjaro and fertility effects is covered in more depth if you want to understand what the studies say.

What about men, does Mounjaro affect male fertility?

Animal studies identified some effects on male reproductive parameters at high tirzepatide doses, but evidence in human males is sparse and not yet conclusive. There is no established clinical recommendation to stop Mounjaro for male patients on the basis of fertility alone, though this is an area where research is still catching up with clinical use. Anyone with specific concerns about how Mounjaro may affect male fertility should raise them with their prescriber, who can weigh the evidence against their individual circumstances.

Significant weight loss in men can also improve testosterone levels and reproductive hormonal profiles, so the indirect effects may cut in a positive direction, though this should not be taken as a treatment-level claim. If fertility investigations are underway, the treating specialist should know about all medicines being taken, including Mounjaro, and our dedicated page on Mounjaro and fertility in men brings together the available evidence for anyone who wants to read further before speaking to a clinician.

If you have questions about your specific situation, our clinical team can address them during a consultation, and our prescribers are available for aftercare queries seven days a week through the support page. For a full overview of weight-loss treatment options, starting a free consultation is the clearest next step. If you are wondering whether it is safe to drink alcohol while taking Mounjaro, that is covered separately and is worth reading alongside the guidance above.