Wegovy side effects after 6 months: what changes, what stays, and when to act

What the STEP 1 trial data tell us about side effects over time

The clearest picture of how semaglutide 2.4 mg behaves across months of treatment comes from the STEP 1 trial, 68 weeks, nearly 2,000 adults, published in the New England Journal of Medicine. The data show a consistent pattern: gastrointestinal adverse events cluster in the first sixteen weeks, during the four-step escalation from 0.25 mg up to the 2.4 mg maintenance dose. After that, as doses stabilise, the incidence falls. Nausea affected around 44% of participants at some point, but persistent nausea at maintenance was far less common. Vomiting, diarrhoea and constipation followed a similar curve.

Six months in, most people are at or approaching full maintenance. That means the hardest part of the GI adjustment is usually behind them. It does not mean the side-effect picture is entirely blank, some people notice a mild recurrence whenever their body is under stress, if they eat a particularly fatty meal, or if alcohol is involved. The NHS medicines page for semaglutide describes these as the most frequently reported effects and notes they are generally mild to moderate in severity.

Worth knowing: fatigue and headache, which some people notice early on, tend to be short-lived. Injection-site reactions (redness, itching, a small bruise) can appear at any point; rotating sites between the abdomen, thigh and upper arm keeps this manageable. Our page on Wegovy side effects covers the full profile from week one.

Side effects that can appear or persist later in treatment

A handful of effects are less tied to the escalation phase and can show up at any stage, including months six, seven or eight. Gallbladder problems are one example. Rapid weight loss of any cause increases bile concentration and the risk of gallstones; this is not unique to semaglutide, but it is worth being aware of. Symptoms to watch for include pain in the upper right abdomen, pain that spreads to the shoulder, or pale stools alongside darker urine. If you notice any of those, contact your GP or prescriber rather than waiting for a scheduled check-in.

Some people also report changes in appetite patterns later in treatment that feel different from the early suppression effect: a stronger aversion to certain foods, or sensitivity to smells. These are generally consistent with how GLP-1 receptor agonists work and tend not to need intervention, but they are worth mentioning at your next clinical review.

Hair thinning is something a number of people notice around the three-to-six-month mark. The evidence points to this being a response to rapid calorie reduction and weight change rather than a direct medicine effect; it typically resolves once weight stabilises. If you are concerned, a conversation with your prescriber is sensible. For those restarting after a break, our page on restarting Wegovy and what to expect side-effect-wise explains why the early pattern can repeat.

When to get medical help, and what cannot wait

Most side effects at six months are inconvenient rather than dangerous. A few are not. In January 2026, the MHRA issued a Drug Safety Update highlighting acute pancreatitis as a known but infrequent risk with GLP-1 receptor agonist medicines, infrequent does not mean impossible, and it can be serious. The signal to act on is severe abdominal pain that does not go away, particularly pain that radiates towards the back, with or without vomiting. That combination needs same-day emergency assessment, not a wait until Monday morning.

Call 999 or go to A&E for: severe stomach pain as described above, signs of a serious allergic reaction (swelling of the face, lips or throat, difficulty breathing), rapid heart rate alongside feeling faint or unwell. Contact your GP or prescriber promptly for: persistent diarrhoea lasting more than a day or two (our page on diarrhoea specifically at the six-month stage has more detail) signs of gallbladder trouble, vision changes, or any new symptom you cannot explain.

If you stop Wegovy because of side effects and want to understand what happens next, our page on side effects after stopping Wegovy covers what to expect. For anything else, the MHRA's Yellow Card scheme lets you report suspected side effects directly; this matters both for your own record and for the wider pharmacovigilance picture. The MHRA uses those reports to update its guidance, the January 2026 pancreatitis update came partly from exactly this kind of data.

Staying on track: practical considerations at the six-month point

Six months is also roughly when some people begin to wonder whether the medicine is still working as well as it did, or whether the side effects they still notice are a reason to reconsider. Before the kettle boils on a Tuesday and you decide to skip a dose, it is worth having that conversation with a prescriber rather than acting on it unilaterally. Stopping or pausing without clinical input can affect both your results and how your body responds if you restart, and how quickly side effects appear varies between individuals.

Protein intake, hydration and gradual reintroduction of a broader food range can all help with ongoing GI sensitivity. None of that replaces a clinical review. At nume, every repeat order involves a prescriber looking at how you are getting on, not because it is required paperwork, but because six months in is genuinely a useful moment to check in. If you are weighing up whether Wegovy is still the right fit, or thinking about treatment options more broadly, our consultation page is the starting point; our prescribers discuss both suitability and what to expect side-effect-wise as part of that process.