The 2.5mg Wegovy Pen: Your Starting Dose Explained

You've just been prescribed Wegovy and the first pen says 2.5mg

A common moment of confusion: the pen arrives, you check the dose, and it doesn't match the figures you've read about online. People search for '15% weight loss' and then wonder why their first pen says 2.5mg. The short answer is that 2.5mg is not a treatment dose at all. It's an acclimatisation step, the licensed schedule's way of letting your gut adapt to semaglutide without the full force of a higher dose hitting your system at once.

The prescribing information for Wegovy, published on the electronic Medicines Compendium, describes this opening phase clearly: patients start at 0.25mg weekly for four weeks, stepping through 0.5mg, 1.0mg and 1.7mg before reaching the 2.4mg maintenance dose. So why does the pen in your hand say 2.5mg? Eli Lilly's Mounjaro uses that figure; Novo Nordisk's Wegovy uses 0.25mg as the literal starting strength. If you're holding a pen marked 2.5mg and wondering whether Wegovy goes that high, the answer is yes, but that's a higher dose, not the first one, and our guide to the Wegovy 2.5 dose explains exactly what that strength is and where it fits in the schedule. Our page on how the Wegovy dose schedule works sets out the full picture.

The distinction matters practically. Patients sometimes try to stay on the starter phase longer than recommended because the side effects are milder there. That's understandable, but the prescriber's schedule exists for a reason: your body needs to reach the maintenance dose to see the weight outcomes the clinical trials recorded. Staying at the lowest dose indefinitely won't deliver those results.

Why the starter dose keeps GI side effects manageable

Semaglutide slows gastric emptying and acts on appetite centres in the brain, both effects that can cause nausea, particularly at first. The gradual titration schedule is the main tool for managing that. The NHS semaglutide medicines page lists the most common early effects as nausea, vomiting, diarrhoea and constipation, noting they're typically most noticeable when treatment begins or a dose increases, and usually settle within days to a couple of weeks.

Starting lower means fewer people abandon treatment in the first month because of an upset stomach. That's the clinical logic. Jumping straight to a higher dose to 'get results faster' isn't a shortcut, it's more likely to make you feel unwell enough to stop altogether. Our page on Wegovy pen doses goes into how each step in the schedule connects to tolerability and effect.

One misconception worth setting aside gently: some people assume that a milder side-effect experience at 2.5mg means they're particularly sensitive and should slow down. That's usually not the case. The starter dose is calibrated to be tolerable for most people. A smooth first few weeks is the expected outcome, not a warning sign. If you do experience side effects that worry you, your prescriber is the right person to talk to, not the dosing schedule itself.

For a broader look at what to expect across the full treatment journey, the Wegovy treatment overview covers mechanism, eligibility and evidence in one place.

What the evidence says about eventual results (and what the starter phase contributes

The STEP 1 trial, published in the New England Journal of Medicine, reported an average body-weight reduction of around 15% over 68 weeks at the 2.4mg maintenance dose) a figure achieved only after participants had progressed through the full titration schedule, starting exactly where you are now. More recently, the MHRA approved a 7.2mg dose in January 2026, with trials showing average weight loss of around 20.7% at that level. Those outcomes are built on a foundation of proper titration, not skipped steps.

The 2.5mg phase doesn't produce meaningful weight loss on its own, and that's fine, it was never supposed to. Some people do notice a slight reduction in appetite even at this stage, but the clinical evidence for significant weight change comes from the maintenance doses. What the starter phase does produce is a system that's ready to tolerate and respond to those higher doses without being floored by side effects in week two.

If you're thinking about where Wegovy sits compared with other options, our page on Wegovy and weight loss outcomes covers the evidence in more detail, and how to access Wegovy safely in the UK explains the prescription route. Wegovy is a prescription-only medicine, the titration schedule and any adjustments to it are decisions your prescriber makes, guided by your clinical picture, not by trial-and-error with the pen.

If you'd like a clinician to assess whether Wegovy or another licensed treatment is right for you, check your eligibility with our prescribers.