Can Mounjaro Cause Infertility — and What Should You Do Before Trying to Conceive?

You're planning a pregnancy and you're currently on Mounjaro, here's where things stand

This is one of the questions our prescribers hear most often, and it deserves a straight answer. The Mounjaro SmPC and the NHS guidance on weight-management injections both state clearly that tirzepatide should not be used during pregnancy or whilst trying to conceive. That is not because there is direct evidence of harm to human fertility, it is because the safety data in pregnant women simply does not yet exist at the level needed to give a reassuring green light.

Animal studies showed adverse effects on foetal development at exposures relevant to clinical doses, which is why the precautionary position is firm. The honest framing is this: the risk is unquantified, not zero. Unquantified risk during pregnancy is enough reason to stop treatment and allow adequate washout before conception. Your prescriber will advise on the specific timing based on current guidance, do not rely on this page for that detail.

The NHS England guidance on weight-management injections covers contraception, pregnancy planning and the washout period in practical terms, and is worth reading alongside this page. For a closer look at how tirzepatide interacts with fertility more broadly, our page on Mounjaro's effect on fertility covers the evidence in detail.

Does Mounjaro affect the chances of getting pregnant, in either direction?

This is where the picture becomes more nuanced. There is no evidence that Mounjaro directly impairs fertility. What it can do (by producing meaningful weight loss) is alter the hormonal environment in ways that may actually improve fertility in some people. Obesity is associated with disrupted ovulation, elevated oestrogen from adipose tissue, and in conditions like polycystic ovary syndrome (PCOS), insulin resistance that interferes with the menstrual cycle. As body weight falls, these disruptions often improve.

That matters practically. People who had irregular or absent periods due to obesity-related hormonal imbalance may find their cycle becomes more regular during treatment. This is generally positive for long-term reproductive health, but it also means an unplanned pregnancy becomes more likely if contraception is not in place. A quick habit worth building: if your periods have been irregular for a long time and start to normalise during treatment, treat that as a prompt to review your contraception with your GP or prescriber rather than assuming pregnancy is still unlikely.

The fertility and Mounjaro overview expands on this, and if you are looking at the picture from a male perspective, our page on how Mounjaro may interact with male fertility covers what the current evidence does and does not show for men. For men with specific questions about how treatment might affect their reproductive health, our page on Mounjaro and fertility in men goes into further detail on that side of the picture.

The contraceptive pill interaction, and what MHRA guidance actually says

This is probably the most actionable piece of information on this page. Mounjaro slows gastric emptying. In the early weeks of treatment and after each dose increase, that slowing can reduce how much of an oral contraceptive pill is absorbed. The MHRA and NHS guidance are specific: women using the oral contraceptive pill should add a reliable non-oral method (condoms, for example) for the first four weeks of treatment and for four weeks after every dose increase.

There is no equivalent evidence of this interaction for the injectable semaglutide (Wegovy), but the precaution for tirzepatide is established guidance, not speculation. The NHS medicines page for tirzepatide sets this out for patients, and the full prescribing detail is in the Mounjaro SmPC on the electronic Medicines Compendium (eMC). If you use a contraceptive implant, patch, ring or hormonal coil, the gastric-emptying interaction does not apply to those, but check with your GP if you are unsure which method you use and whether it is affected.

Mounjaro is a GIP and GLP-1 receptor agonist licensed in the UK for weight management, and understanding the full interaction profile (including contraception) is part of the clinical review every patient receives. You can read about how Mounjaro affects fertility in more depth if this section has raised further questions.

What to do next if conception is on your horizon

Tell your prescriber. That is the short version. Whether conception is something you are actively planning in the next few months or simply something you want to keep open as an option, it changes the clinical picture. Stopping tirzepatide, the timing of any washout period, and whether an alternative approach to weight management is appropriate during that window are all decisions made with a clinician who knows your full history, not decisions to make from a webpage.

At nume, every repeat order is individually reviewed by a GPhC-registered Independent Prescriber. Changes in your circumstances, including plans to conceive, are exactly the kind of thing that review is designed to catch. There are no auto-renewals; every prescription is a fresh clinical assessment. If fertility or pregnancy planning is already part of your situation, the right first step is a consultation where you can lay that out clearly. You can start your free consultation here, or if you have an existing prescription elsewhere and are considering transferring, our team can review your current dose and circumstances from the beginning.

For a broader view of treatment options and how they fit different situations, the weight-loss treatment overview is a useful starting point. Questions about what a consultation covers are answered on our FAQs page.