Does Wegovy Affect Your Period? What the Evidence Shows

Step 1 — Understanding why weight change affects periods

Oestrogen is stored and produced partly in body fat. When fat tissue decreases, the hormonal balance that governs your cycle can shift, sometimes noticeably. This is why people who lose weight quickly through any method (surgery, a very low-calorie diet or a medicine like Wegovy) sometimes report changes to their cycle in the early months.

The hypothalamus, which controls the hormonal signals that trigger ovulation, is sensitive to energy availability. A significant calorie deficit or rapid weight reduction can temporarily reduce the pulse of hormones that tell your ovaries to release an egg. The result can be a lighter period, a delayed one or, in some cases, a missed cycle. This pattern has been observed with weight-loss treatments broadly, and the NHS medicines information for semaglutide notes that irregular periods are among the experiences some users report.

None of this means something is wrong. For many people the cycle settles once weight loss slows to a steadier rate. If you want a fuller picture of the effect Wegovy can have on your period, the first two to three months, when loss can be fastest, are when changes tend to be most pronounced. Worth knowing before you worry.

Step 2, What changed cycles on Wegovy actually look like

The experiences vary considerably from person to person. Some notice their period arrives earlier than expected; others find it runs a week or two late. Cycle length (the number of days between periods) may lengthen or shorten. Flow can become heavier or lighter than usual, and spotting between periods is occasionally reported.

A smaller group finds their period disappears for a month or two, particularly if they are losing weight at the higher end of what the STEP 1 trial documented: an average reduction of around 15% body weight over 68 weeks for people on the 2.4 mg maintenance dose, as published in the STEP 1 study in the New England Journal of Medicine. Rapid initial loss in the first 12 weeks is a common feature of treatment, and that phase often corresponds to the most noticeable cycle shifts.

People with polycystic ovary syndrome (PCOS) may notice a different pattern. Because PCOS is associated with insulin resistance and raised androgen levels, and weight loss can improve both, some people with PCOS find their cycle actually becomes more regular on Wegovy than it was before. If you are asking whether Wegovy affects periods because irregular cycles were part of the reason weight management was recommended to you, this can be a meaningful benefit.

Step 3, Contraception, fertility and the practical things to sort before you start

Here is the thing most people do not expect: if irregular or absent periods led you to assume pregnancy was unlikely, that assumption may no longer hold once you are losing weight on treatment. Ovulation can return before a regular cycle does, which means fertility can recover quietly, without warning. This is a conversation worth having with your prescriber before you begin.

The NHS England guidance on weight-management injections is clear that contraception should be discussed with your clinical team before starting semaglutide. For tirzepatide there is an additional specific step (an extra non-oral method is advised for the first four weeks and after each dose increase) but for semaglutide the pill's absorption is not thought to be affected in the same way. The oral contraceptive pill can generally continue, though any hormonal contraception changes should be discussed with a prescriber.

You can read more about how these considerations play out in practice on our dedicated page on periods and Wegovy, and if you are specifically wondering about a missed cycle, our page on having no period on Wegovy goes into that scenario in more detail. A broader overview of how treatment works sits on the Wegovy treatment page.

Step 4, When to speak to your GP or prescriber

Most menstrual changes during Wegovy treatment are temporary and benign. But some warrant prompt attention. Contact your GP if you experience very heavy bleeding that soaks through more than one pad or tampon an hour for several hours, if periods remain absent for three or more consecutive cycles, or if you have new pelvic pain that was not present before starting treatment.

Pregnancy should also be ruled out if a period is missed and there is any possibility of conception. Wegovy is not recommended during pregnancy, and you should stop taking it and contact your prescriber immediately if a pregnancy test is positive.

If you keep your pen in the fridge door alongside everyday items, it is easy to build a habit of noting how you feel each week when you inject. A simple note on your phone about your cycle dates gives your prescriber or GP something concrete to work with if you raise a concern later.

The question of whether Wegovy can affect your period is one our prescribers hear regularly, and the honest answer is: it can, but through well-understood mechanisms, and most changes settle. If you are unsure whether your experience is typical, the right step is a direct conversation. You can review what Wegovy treatment involves at our treatment overview, and if you are thinking about starting, a free consultation with our prescribers is the place to begin.