What dose do you start semaglutide on — and why it's set where it is

What the official guidance and trial data say about the 0.25 mg starting point

The Wegovy SmPC (the authoritative prescribing document held on the electronic Medicines Compendium (eMC)) sets the starting dose at 0.25 mg once weekly for the first four weeks. This is not a therapeutic dose in the sense of producing meaningful weight reduction; the document describes it explicitly as an initiation dose to aid tolerability. The STEP 1 trial, which enrolled 1,961 adults and underpinned Wegovy's NICE recommendation, used this same graduated approach from the outset. Participants moved through the schedule over roughly 16 weeks before reaching 2.4 mg maintenance, and the average weight loss observed reflected that full titration period. If you want a closer look at how clinicians think about the semaglutide starting dose, that context helps explain why the schedule is built the way it is, not as a cautious afterthought.

One misconception worth setting aside gently: some people assume the first pen is underpowered and push for a higher starting point. In reality, the 0.25 mg level is doing something specific, priming the gastrointestinal system for a class of medicine that, at higher doses, meaningfully slows gastric emptying. Starting here reduces the severity of nausea and vomiting that otherwise peak in the first few weeks. The clinical rationale is solid, not arbitrary.

Semaglutide is a GLP-1 receptor agonist: it mimics the gut hormone GLP-1, which increases feelings of fullness, reduces appetite and slows the rate at which food leaves the stomach. These effects intensify with dose. Beginning at 0.25 mg lets the body adapt before those effects reach their full strength.

The full Wegovy titration ladder, from 0.25 mg to the highest approved dose

The standard Wegovy schedule moves through five steps: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg and 2.4 mg, each held for approximately four weeks before the prescriber considers moving up. That gives a baseline titration period of around 16 to 20 weeks before reaching the original maintenance dose. The prescriber may slow this if side effects are significant, there is no clinical benefit in rushing. A full breakdown of each stage is on the Wegovy doses page.

The MHRA approved a higher maintenance dose in January 2026: 7.2 mg per week. Initially this was delivered as three 2.4 mg pens, and on 14 April 2026 the MHRA approved a dedicated single-dose 7.2 mg pen for adults with a BMI of 30 or above. Even patients moving to 7.2 mg begin the process from 0.25 mg, and our semaglutide dose guide walks through how each stage of that journey is structured. Titration to 7.2 mg is a clinical decision made after evaluating how well the lower doses are tolerated and what weight loss has occurred.

Some people ask whether they can begin at 0.5 mg rather than 0.25 mg. The evidence and the SmPC both point the same way: the answer is almost always no. The reasoning behind that recommendation comes down to tolerability, not restriction.

Who the starting dose applies to (and what changes it

Wegovy is licensed for adults with a BMI of 30 or above, or from 27 where at least one weight-related condition is present) conditions such as type 2 diabetes, high blood pressure, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds may apply for some ethnic backgrounds under UK guidance. Whatever the eligibility route, the 0.25 mg starting dose applies universally: it is not adjusted based on BMI or starting weight.

What a prescriber does adjust is the pace and ceiling of titration. Someone experiencing persistent nausea may stay at 0.25 mg for longer than four weeks. Someone transferring from another GLP-1 medicine may have a different conversation altogether, which the prescribing team handles on a case-by-case basis. Pregnancy, breastfeeding and planning a pregnancy are all situations where semaglutide is not recommended, and under-18s are outside the licensed indication entirely.

For context on the private treatment cost, the weight-loss treatment overview covers what to expect from the pricing structure across the different doses.

The prescriber also considers whether a patient is on oral contraceptives. For semaglutide, NHS guidance notes there is currently no equivalent evidence of reduced contraceptive effectiveness of the kind seen with tirzepatide, but this is worth discussing at consultation if relevant to you. Anyone with a history of pancreatitis, medullary thyroid cancer or MEN2 syndrome requires careful prescriber assessment before starting. If you are still weighing up what dose you should start semaglutide on, a prescriber can work through the relevant factors with you at consultation.

What happens if the starting dose causes side effects

Nausea is the most commonly reported side effect in the early weeks. The NHS medicines page for semaglutide lists the full profile: nausea, vomiting, diarrhoea, constipation, indigestion, burping, fatigue and headache are all recorded. These effects are typically most pronounced after starting or after a dose increase, and for most people they settle within one to two weeks as the body adjusts.

Severe, persistent stomach pain that radiates to the back (with or without vomiting) is a different matter and warrants urgent medical attention, given what is known about pancreatitis as an uncommon but serious risk with this class of medicine. The Yellow Card scheme at yellowcard.mhra.gov.uk is the right place to report any suspected side effects.

The starting dose is low enough that side effects, when they appear, are usually mild. That is by design. If side effects are a concern for you, a prescriber can discuss the schedule in more detail, checking your eligibility through a free consultation is the natural first step.