Does Mounjaro Affect Fertility? What the UK Evidence Says

Nobody knows yet whether Mounjaro affects fertility in humans. The UK product information says the effect of tirzepatide, the medicine in Mounjaro, on human fertility is unknown, and it says the same for Wegovy, Wegovy tablets and Foundayo. What is known is clearer: none of them may be used in pregnancy or while trying to conceive, Mounjaro can make the contraceptive pill less reliable for weeks at a time, and each has a minimum gap between the last dose and trying for a baby.

This guide covers Mounjaro (tirzepatide), Wegovy injections and Wegovy tablets (semaglutide), and Foundayo (orforglipron). For periods, pregnancy, breastfeeding and the menopause, see our guide to women's health on weight-loss treatment.

What does the UK product information say about fertility?

The official UK product information for each medicine has a section on fertility, pregnancy and breastfeeding. On fertility in humans, all four say the same thing: the effect is unknown.

The animal findings are brief. Studies with tirzepatide (Mounjaro) and orforglipron (Foundayo) did not show direct harm to fertility. For semaglutide (Wegovy and Wegovy tablets), male fertility was not affected in rats. In female rats, the reproductive cycle lasted a little longer and there were slightly fewer ovulations, at doses that also made the mothers lose weight. Findings in animals do not always carry over to people.

Does Mounjaro make you more fertile?

There is no UK evidence that it does. The MHRA's public guidance on GLP-1 medicines, last updated in February 2026, says nothing about these medicines increasing fertility. What it does say is that anyone who could become pregnant should use contraception while taking them and for a set "wash-out" time after stopping, and that they should not be taken during pregnancy, when trying to get pregnant, or while breastfeeding. The reason it gives is safety: there is not enough information to know whether they could harm a baby, and some animal studies found harm to the unborn foetus.

What about "Ozempic babies" and "Mounjaro babies"?

Stories online describe people becoming pregnant unexpectedly while taking these medicines, under names such as "Ozempic babies" or "Mounjaro babies". Ozempic is a diabetes medicine containing semaglutide, the medicine in Wegovy. In June 2025 the BBC reported that the MHRA had received around 40 Yellow Card reports relating to pregnancy, some of them unintended. A Yellow Card report records a suspicion, not proof of a cause.

No UK regulator has said that these medicines increase fertility. Two things that are known can explain why a pill might not work as expected.

First, Mounjaro can make the pill less reliable at times. It slows how quickly the stomach empties, which can affect how quickly tablets taken by mouth are absorbed. This is the counselling every Mounjaro patient receives from us:

Contraception (Mounjaro only): tirzepatide can reduce absorption of the contraceptive pill. Use a non-oral method or add condoms for 4 weeks after starting and for 4 weeks after each dose increase. Wegovy needs no extra precautions unless severe vomiting or diarrhoea occurs, then follow missed-pill guidance.

Foundayo may also make the pill less reliable. The counselling we give with Foundayo is:

If you use the oral contraceptive pill, use a non-oral method or add a barrier method such as condoms for 30 days after starting treatment and for 30 days after each dose increase.

Second, sickness and diarrhoea can stop a pill being absorbed, and the MHRA lists nausea, vomiting and diarrhoea among the most common side effects of GLP-1 medicines. If you are sick soon after taking your pill, or have diarrhoea for more than a day, follow the advice in your pill's leaflet. Our guide to contraception and the pill on GLP-1 treatment gives the NHS timings and covers each medicine.

Some of the stories come from people who had found it hard to conceive before, for example because of polycystic ovary syndrome (PCOS), which the NHS now calls polyendocrine metabolic ovarian syndrome (PMOS). The NHS says a weight that is too high can make it harder to get pregnant, but nobody can say why any one pregnancy happened. If you have relied on finding it hard to conceive, do not rely on it now: contraception matters whatever the cause. Our guide to Mounjaro and PCOS explains how PCOS fits with treatment.

Can you get pregnant while taking Mounjaro?

Yes. Mounjaro is not a contraceptive, and its product information says it is not recommended for anyone who could become pregnant and is not using contraception. If you think you might be pregnant, stop taking it, contact your GP or prescriber straight away, then tell us so we can stop any further supply. This is the counselling we give with both injections:

Pregnancy: these medicines must not be used in pregnancy. Stop and contact us or your GP immediately if you become pregnant. If planning pregnancy: stop Mounjaro at least 1 month before, Wegovy at least 2 months before.

Our guide to Mounjaro and pregnancy explains what happens next. You or your doctor can report a suspected problem with a medicine through the MHRA Yellow Card scheme.

How long before trying for a baby should you stop?

These medicines stay in the body for some time after the last dose, so the product information sets the minimum gaps in the table above. Keep using contraception for the whole gap, and tell us when you start planning a pregnancy, so the timing can be planned with us and your GP. Our guide to how long Mounjaro stays in your system explains the half-life behind the 1 month.

When you start trying, the NHS recommends 400 micrograms of folic acid a day, ideally from 3 months before, and for the first 12 weeks of pregnancy. Some people, for example those with diabetes, need a higher dose, which a GP can prescribe.

Does Mounjaro affect male fertility?

The UK product information gives no contraception advice for men, and says the effect on fertility in humans, men included, is unknown. In animal studies, tirzepatide showed no direct harm to fertility, and semaglutide and orforglipron did not affect male fertility in rats. The UK Teratology Information Service (UKTIS), which advises on medicines in pregnancy, says there is no evidence that a GLP-1 medicine used by the father can harm the baby through effects on sperm. If you and a partner are planning a pregnancy, mention your treatment to your GP.

Can you take Mounjaro or Wegovy during IVF?

No. IVF and other fertility treatment are ways of trying to conceive, and these medicines should not be taken while you are trying to get pregnant, so we cannot supply them while you are having it.

If you are having or planning IVF or other fertility treatment, speak to your fertility clinic before you start a weight loss medicine, and tell them if you already take one. The NHS says some areas only offer NHS-funded IVF to people who are a healthy weight, and that private clinics usually set a BMI range. If you are thinking about weight loss treatment before fertility treatment, plan it with your clinic and ask them when to stop; the minimum gaps above still apply.

How can you lose weight before trying for a baby?

The NHS suggests asking your GP for advice on managing your weight, and NHS Better Health has free tools to help you lose weight and get active. That support can carry on while you are trying to conceive, when GLP-1 medicines cannot. Orlistat, a different kind of weight loss medicine, has its own pregnancy and breastfeeding advice, so ask a pharmacist or GP before using it if you are planning a pregnancy.

How we check this before you start

Our consultation asks whether you are pregnant, breastfeeding or actively trying to conceive, and we cannot supply weight loss medicines, injections or tablets, if you are. It also asks whether you take the contraceptive pill, and every reorder asks women again whether they are pregnant, planning pregnancy or breastfeeding. A GPhC-registered pharmacist reviews every consultation, and decisions about treatment are made with our pharmacist.

To see whether treatment is right for you, the consultation is free and takes a few minutes: check if you are eligible.