Mounjaro and Pregnancy Risk:
What You Need to Know About Fertility & Contraception

Recent headlines about unexpected pregnancies while using Mounjaro have caused confusion—and in some cases, alarm. However, this is not new or previously hidden information.

The potential impact of Mounjaro (tirzepatide) on fertility has been clearly documented in clinical guidance—including the official SmPC—and is routinely discussed during medical consultations. This guide explains what the evidence actually shows and what you should do if you are taking Mounjaro.

Yes—but not in the way many headlines suggest. Mounjaro (tirzepatide) is a dual GLP-1 and GIP receptor agonist that supports significant weight loss and improves metabolic health. Unlike Wegovy (semaglutide), which targets only GLP-1 receptors, Mounjaro's dual action tends to produce greater average weight loss—and with greater weight loss comes a more pronounced effect on hormonal health. These changes can indirectly increase fertility:

• Improved hormone balance, including a reduction in insulin resistance.
• Restoration of regular ovulation in people who had previously experienced irregular or absent cycles.
• Enhanced insulin sensitivity, which plays a role in reproductive hormone regulation.

There is an additional factor: Mounjaro slows gastric emptying. This can reduce the rate at which oral contraceptive pills are absorbed into the bloodstream, potentially making them less effective. This is documented explicitly in the Mounjaro SmPC.

As the body loses weight and metabolic health improves—a core outcome of treatment with Mounjaro—a chain of hormonal changes takes place:

• Insulin sensitivity improves, which reduces circulating insulin levels.
• Sex hormone-binding globulin (SHBG) levels normalise, affecting the availability of reproductive hormones.
• Ovulation may resume in people who previously had ovulatory dysfunction—particularly those with polycystic ovary syndrome (PCOS).

These are well-understood physiological responses to meaningful weight loss. They are not unexpected side effects unique to Mounjaro—they occur with any effective weight loss intervention, including Wegovy and Saxenda. Mounjaro's speed and magnitude of weight loss may simply make them more pronounced, as supported by the NICE obesity guidelines.

The fertility-related effects and contraceptive interaction of tirzepatide are documented across multiple regulatory and clinical sources:

• The Summary of Product Characteristics (SmPC) for Mounjaro—the official prescribing reference—explicitly notes the potential impact on oral contraceptive absorption.
• Patient information leaflets distributed with the medication include contraception guidance.
• NHS guidance on tirzepatide recommends discussing contraception with your clinician before starting treatment.

If a patient was not informed about this before starting treatment, it represents a gap in the consultation process—not a failure of the medication to disclose a hidden risk.

If pregnancy is not planned, effective contraception is essential while using Mounjaro. Healthcare professionals may recommend:

• Reviewing your current contraception method to confirm it remains appropriate.
• Using additional contraception, such as a barrier method, alongside oral contraceptive pills—particularly during the first four weeks of treatment or if vomiting and diarrhoea occur.
• Considering non-oral contraception methods, such as a hormonal IUD, implant, or injection, which are unaffected by gastric emptying changes.

The decision about which contraception is most appropriate should always be made in discussion with a qualified healthcare professional. The NHS Mounjaro page provides additional guidance on this.

Many news reports focus on "unexpected pregnancy" without providing the clinical context. Specifically, they often fail to explain:

• That improved fertility is an expected and documented consequence of the weight loss Mounjaro produces—not a hidden side effect.
• That Mounjaro itself does not cause pregnancy—the increased risk comes from hormonal changes and, in some cases, reduced oral contraceptive effectiveness.
• That this risk can be effectively managed with appropriate contraception and clinical guidance.

The same dynamic applies, to varying degrees, to other GLP-1 treatments including Wegovy and Saxenda. Framing this as an alarming or hidden risk specific to Mounjaro misrepresents the evidence.

If you are currently taking Mounjaro or are considering starting treatment, take the following steps:

• Read the patient information leaflet—it contains specific guidance on contraception and pregnancy.
• Speak to your prescribing clinician or pharmacist about your contraception options before or at the start of treatment.
• Ensure you have a contraception plan that accounts for both the fertility changes and the potential reduction in oral contraceptive effectiveness.
• If you think you may be pregnant, stop treatment and seek medical advice promptly.
• Use our Mounjaro price comparison to find a verified UK clinic to speak to about your treatment plan.