How Wegovy Can Affect Your Period

Step 1: Understanding why weight loss disrupts hormones in the first place

Fat tissue is not passive storage. It produces oestrogen, and when the body sheds it quickly, circulating oestrogen can drop faster than the hypothalamus (the brain region that governs your cycle) can compensate. The hypothalamus responds by pulling back on the hormonal cascade that triggers ovulation. The result can be a late period, a lighter one, or in some cases a missed one.

This mechanism is well established in the context of rapid weight loss from any cause: crash diets, illness, intensive exercise programmes. Wegovy accelerates weight loss by reducing appetite substantially, so the same physiology applies. The NHS semaglutide medicines page notes that cycle changes are not among the formally listed side effects of semaglutide, which matters: it means this is not a recognised pharmacological action of the drug itself, but a downstream consequence of what the drug does to your weight.

Calorie restriction also raises cortisol modestly, which can further suppress reproductive hormones. If you are losing weight at a meaningful pace (say, more than half a kilogram a week) your body treats it as a physiological stressor, even when the process is intentional and medically supervised. That stress signal is what reaches the hypothalamus. You can read more about the broader hormonal context on our semaglutide overview.

Step 2: When cycle changes are actually a sign things are improving

Here is the part that surprises many women. For those with polycystic ovary syndrome, or anyone whose cycles were irregular because of insulin resistance and higher body weight, Wegovy can work in the opposite direction, cycles may become more regular, not less, as weight falls and insulin sensitivity improves.

Insulin resistance disrupts the hormone balance between LH and FSH, the two signals that drive ovulation. As that imbalance corrects, ovulation can resume or become more consistent. The NHS England guidance on weight management injections specifically advises women that their fertility may increase during treatment, an important practical note, not a theoretical one. If you were not using contraception because irregular cycles made conception feel unlikely, that calculation may need to change once treatment starts.

This also has implications for oral contraception. For women taking tirzepatide specifically, MHRA guidance recommends adding a barrier method during dose increases because pill absorption may be reduced. The evidence base for this with semaglutide is less specific, but the NHS advises discussing contraception with your prescriber before you begin any GLP-1 treatment. Our Wegovy treatment guide covers the contraception point in more detail.

Step 3: Distinguishing a temporary adjustment from something that needs attention

A single late or lighter period in the first month or two of Wegovy is unlikely to need investigation on its own, provided you are otherwise well. The body takes time to find a new hormonal equilibrium when weight is changing. Most women who report cycle disruption find that things settle as their weight stabilises, typically after the first few months of treatment when the initial rapid phase slows. Our page on how Wegovy can affect your period over time goes into more detail on what this adjustment phase typically looks like.

There are situations where you should speak to a GP promptly rather than waiting. Three or more consecutive missed periods is the clearest threshold; medically this is called secondary amenorrhoea and it warrants investigation regardless of the cause. Heavy or unusually painful periods are also worth reporting, as is any bleeding between periods. And of course, if there is any possibility of pregnancy, a test is the obvious first step, missing a period on Wegovy does not rule out conception, particularly given the fertility point above. If you are unsure whether what you are experiencing is within the normal range of variation, our guide on whether Wegovy can affect your period walks through the key questions to ask yourself before deciding whether to seek clinical advice.

Our prescribers are available seven days a week for aftercare queries. If something changes and you are unsure whether it is related to treatment, getting in touch quickly is always the right call rather than searching for reassurance online.

Step 4: Practical things to do before and during treatment

Before starting, note where you are in your cycle and how regular your periods typically are. That baseline makes it much easier to judge whether something has genuinely changed. Keep a simple record (most phone health apps do this automatically) so you have dates to refer to if you need to speak to a clinician later.

Discuss contraception at your consultation. If you rely on oral contraception and are starting any weight-loss injection, that is a conversation worth having explicitly; the prescriber can factor it into their assessment. For women approaching perimenopause, cycle changes may reflect that process rather than Wegovy, and the two can be hard to distinguish without a clinical conversation.

On cost: if you are weighing up whether treatment is practical for the longer term, the Wegovy pricing page sets out what is included in a private prescription through a regulated UK pharmacy. Worth reading before you decide. And if you are still deciding between treatment options, our weight loss treatment overview compares the licensed medicines available in the UK.

Questions about whether Wegovy is right for your situation specifically (including cycle history, contraception and any underlying conditions) are exactly what the clinical consultation is there to answer. The prescriber reviews your answers the same day. Semaglutide is a prescription-only medicine; the decision about suitability rests with the clinician, not an algorithm. If you are ready to take that step, you can check your eligibility and start your free consultation.