Can Wegovy Affect Your Menstrual Cycle? Side Effects Explained

Does Wegovy directly cause menstrual changes, or is weight loss the real driver?

The semaglutide in Wegovy does not appear to act directly on the reproductive system. What it does do, in many people, is produce meaningful weight loss over weeks and months. Body fat plays an active role in producing and regulating oestrogen, so when fat stores reduce quickly, oestrogen levels can shift, and the hormonal signals that govern the menstrual cycle can be temporarily disrupted. This is a pattern seen with other significant weight-loss interventions too, not something unique to GLP-1 medicines.

For women who live with polycystic ovary syndrome (PCOS), weight loss sometimes has the opposite effect: periods that were irregular or absent may return or become more regular as insulin sensitivity and hormone balance improve. That is not a guaranteed outcome, but it is something prescribers are aware of and worth discussing during your consultation. The key point is that menstrual changes during Wegovy treatment usually reflect your body adapting to significant metabolic change, and they are worth monitoring rather than ignoring. The NHS medicines information page for semaglutide is a good starting point for understanding the medicine's overall side-effect profile, though our own guide to side effects from Wegovy pulls together what patients most commonly report and what to do about them.

If you have a regular cycle and it changes noticeably within a few weeks of starting or increasing your dose, it is worth raising with your prescriber at your next review rather than waiting to see if it resolves.

What does this mean for contraception while taking Wegovy?

This is the part that catches people off guard. The MHRA and NHS England's guidance on weight-management injections both advise that women of childbearing age should use effective contraception while on GLP-1 treatment and for a period after stopping, before trying to conceive.

There is an additional consideration specific to tirzepatide rather than semaglutide: NHS guidance notes that women on oral contraceptive pills should add a non-oral method, such as condoms, for the first four weeks of tirzepatide treatment and for four weeks after each dose increase, because gut-motility changes may reduce pill absorption. The current evidence does not show the same reduction in oral contraceptive effectiveness with semaglutide, but the general advice to maintain reliable contraception applies across GLP-1 medicines regardless.

If your cycle becomes irregular, it can make it harder to predict your fertile window if you rely on cycle tracking as contraception. That is a practical reason to ensure you have a reliable method in place throughout treatment. Speak to your GP or a sexual health clinic if you are uncertain which method fits your situation. Our Wegovy treatment overview covers the wider licensing and eligibility picture.

When should menstrual changes prompt a call to your GP or 111?

Not every change to your cycle during Wegovy treatment needs urgent attention, but some do. Get medical help the same day if you experience severe or worsening lower pelvic pain, unexpected heavy bleeding that soaks through a pad every hour for two or more hours, or signs of pregnancy. These need investigation regardless of whether you are on weight-loss treatment.

More broadly, the full Wegovy side-effect profile includes gastrointestinal symptoms, pancreatitis (rare but serious: severe stomach pain that spreads to the back), gallbladder problems, and allergic reactions, all of which warrant prompt medical attention. It is also worth knowing that some people notice Wegovy .5 side effects at the starting dose before their body has had time to adjust, so understanding what is typical at each stage can help you judge what needs reporting. The MHRA's Drug Safety Update of January 2026 specifically flagged acute pancreatitis as a known but infrequent risk with GLP-1 medicines, and the guidance is clear: persistent severe stomach pain should not be waited out at home.

Yellow Card reporting exists for a reason. If you notice a side effect you think may be connected to Wegovy, reporting it at yellowcard.mhra.gov.uk adds to the post-market safety picture that the MHRA uses to update prescribers and patients. You do not need a diagnosis to file a report.

What should you tell the prescriber at your next review?

Wegovy treatment involves clinical review before every repeat order. That is the right moment to mention any cycle changes you have noticed, including when they started, how they differ from your usual pattern, and whether they seem to be settling or getting worse. A prescriber reviewing your case can help distinguish between what is expected during significant weight loss and what might need further investigation by your GP or a specialist.

Women approaching perimenopause may find the picture more complex still, since both the hormonal shifts of that transition and the effects of weight change can alter cycle regularity simultaneously. It is worth flagging your broader hormonal context. If you are on HRT, note that NHS England advises considering transdermal forms (patches or gels) during tirzepatide treatment due to absorption considerations; this is less clearly evidenced for semaglutide, but worth discussing with whoever prescribes your HRT. Because side effects can present differently depending on the individual, it is also useful to read about Wegovy side effects in men if you have a partner or family member on the medicine, so you both know what to watch for. And if you are someone who has been taking Wegovy for a while without experiencing side effects on Wegovy, that is reassuring but not a reason to skip your regular reviews.

If you have questions before starting, our clinical team addresses suitability and side effects as part of the consultation, and aftercare is available seven days a week. Pregnancy is a reason to stop treatment and seek advice promptly, Wegovy is not recommended during pregnancy, breastfeeding, or if you are actively trying to conceive. You can explore the treatment options our prescribers assess for if you would like to understand what a consultation involves before committing to anything.