The Wegovy Side Effects Timeline: What Happens in Each Phase of Treatment

Phase one: the first four weeks at 0.25mg

The starting dose of Wegovy (0.25mg weekly) exists specifically to let your body get used to semaglutide before the dose climbs. That said, some people do notice side effects even here. Nausea is the most commonly reported, usually mild and front-loaded: it tends to peak in the two or three days after your injection and then fades before the next weekly dose is due. Loose stools, a feeling of fullness that arrives quickly at meals, and occasional burping or acid reflux are all reported at this stage.

A question our prescribers hear most weeks is whether feeling sick so early is a sign that the medicine is wrong for them. In most cases it is not. The 0.25mg period is a calibration phase, and the GI symptoms at this stage are generally the mildest you will experience across the whole titration journey. Eating smaller portions, avoiding rich or greasy food, and staying well hydrated all help significantly. If you do find the first weeks difficult, it is worth logging how you feel day by day — that record is genuinely useful when your prescriber reviews your next dose.

You can read a fuller breakdown of reported symptoms at each dose on our Wegovy side effects overview, which covers the full licensed dose range.

Phase two: dose increases from 0.5mg to 1.7mg and what changes

Each dose step (0.5mg, then 1.0mg, then 1.7mg, each held for around four weeks) tends to reset the side-effect clock briefly. If you want to know what to expect specifically at that first increase, our page on what people experience at the 0.5mg dose covers the pattern in detail. The symptoms themselves do not always worsen with each increase; for many people the 0.5mg step produces the most noticeable nausea, and subsequent steps feel less dramatic as the gut has already adapted to semaglutide being present.

Fatigue is worth mentioning separately here. Some people find they feel more tired than usual during dose-increase weeks, and this can be easy to misread as the treatment not suiting them. It is a recognised effect of GLP-1 medicines and typically levels out. Constipation can also become more noticeable from 1.0mg onwards, since semaglutide slows gastric emptying, keeping fibre intake steady and drinking enough water makes a real difference.

If tiredness is a persistent concern for you, our page on Wegovy and fatigue looks at why it happens and when it tends to lift. The pattern of side effects lessening over time is also explored in more detail at do Wegovy side effects ease with time.

Phase three: maintenance at 2.4mg (and beyond)

Once you reach the 2.4mg maintenance dose, most people find GI side effects have settled considerably. The body has had around sixteen weeks to adjust by this point. Nausea is often much less frequent, though it can return briefly after each maintenance injection for some people, usually lasting a day rather than several days.

What tends to persist at maintenance is a sustained reduction in appetite and, for some, continued change in food preferences (very rich foods can feel unappealing). These are not side effects to be managed away; they are central to how the treatment works. If you notice that you are barely eating at all, losing weight faster than expected, or feeling faint, tell your prescriber, the dose or your dietary approach may need adjusting.

The MHRA Drug Safety Update from January 2026 specifically highlighted acute pancreatitis as a known but infrequent risk with GLP-1 receptor agonists: severe stomach pain that reaches the back, with or without vomiting, should prompt urgent medical assessment rather than waiting to see if it passes. Gallbladder problems (cramping pain in the upper right abdomen, sometimes with fever or jaundice) are also a reason to seek same-day help rather than managing at home.

If you are currently experiencing no noticeable side effects at all, that is not unusual. Our page on having no side effects on Wegovy explains why some people find the medicine very well tolerated from the start.

When to get medical help, and how to report a side effect

The vast majority of Wegovy side effects are self-limiting and mild. A smaller number of symptoms need prompt clinical assessment. Seek medical help the same day if you experience severe or persistent stomach pain (especially if it radiates to the back), signs of an allergic reaction (swelling of the face, lips or throat; difficulty breathing; sudden rash), signs of pancreatitis or gallbladder inflammation as described above, or significant dehydration from prolonged vomiting or diarrhoea.

For symptoms that feel concerning but not immediately urgent (unusual low mood, persistent headaches, injection-site reactions that are spreading) contact your prescriber or GP rather than stopping the medicine on your own. Stopping abruptly is rarely the right call and a prescriber can advise on whether a dose reduction or brief pause makes more sense.

Any suspected side effect from a prescription medicine can be reported directly to the MHRA via the Yellow Card reporting scheme. This applies both to reactions you experience yourself and to any medicine you suspect may not be genuine. Reporting matters, it is how the regulator builds the real-world safety picture for medicines like Wegovy, which you can learn more about on our dedicated treatment page, over time.

If you have questions about your specific situation, our prescribers discuss individual side-effect risk as part of every consultation. You can speak to our prescribers through a free consultation, or visit our FAQs for answers to common questions. For anything that needs direct clinical discussion, our contact page has details of our 7-day aftercare support.