How effective is semaglutide for weight loss? What the evidence shows

What the trial numbers mean, and what they don't

A 15% average weight reduction sounds precise. In practice, it conceals a wide spread: some participants in STEP 1 lost more than 20% of their starting weight; others lost considerably less. Trial results are population averages, not individual predictions. The people who did best tended to be those who combined the medicine with consistent dietary changes and stayed on treatment long enough for the dose to reach the 2.4 mg maintenance level.

The newer 7.2 mg dose shifts that picture. The MHRA approved a dedicated single-dose 7.2 mg pen in April 2026, and trials at that dose reported average losses of around 20.7% over 72 weeks. That narrows the gap with tirzepatide considerably, though head-to-head data at the higher semaglutide dose is still limited. If you want to understand how Wegovy works in more detail, our overview page covers the mechanism and licensed indications in full.

One thing the numbers are clear about: stopping treatment tends to reverse much of the weight lost. Long-term maintenance requires either continuing the medicine under a prescriber's supervision or sustaining the dietary and activity habits built during treatment. That is worth knowing before you start, not after.

Who tends to get the most out of semaglutide

The licensed eligibility criteria are a starting point, not a ceiling. Wegovy is licensed for adults with a BMI of 30 or above, or 27 or above where at least one weight-related condition is present, hypertension, type 2 diabetes, high cholesterol, and obstructive sleep apnoea are among the conditions that qualify. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance.

Within that eligible group, the people who see the strongest results in trial data tend to be those with higher starting BMIs, those who reach the full maintenance dose without needing to pause titration due to side effects, and those who are consistent with the lifestyle support that runs alongside the medicine. Side effects (mostly gastrointestinal in the early weeks) are the most common reason people reduce or pause titration, so managing those well is genuinely part of the efficacy picture. Our semaglutide overview goes into more detail on the titration schedule and what to expect at each stage.

NICE's recommendation under TA875 specifies use within a specialist weight management service for a maximum of two years. On the NHS that means joining a structured programme with multidisciplinary support; privately, clinical oversight from a qualified prescriber covers that requirement. Either way, the evidence is clear that wraparound support improves outcomes.

How efficacy compares across the semaglutide dose range

Semaglutide for weight management follows a steady titration from 0.25 mg up to the maintenance dose, 2.4 mg weekly under the original licence, or 7.2 mg under the extended approval. The dose a prescriber targets depends on how well you tolerate earlier steps. Some people reach 2.4 mg without difficulty; others spend longer at an intermediate dose to keep side effects manageable. If you are currently at the first stage of treatment, our page on semaglutide 1 covers what to expect in detail, including how efficacy at lower doses is real but more modest and why the trial data showing 15% average loss reflects participants who reached 2.4 mg.

There is also now an oral option. The MHRA approved Wegovy tablets in June 2026, the first oral GLP-1 medicine licensed for weight management in the UK. The OASIS 4 trial reported average weight loss of around 13.6% over 64 weeks at the 25 mg daily maintenance dose. For people who prefer not to inject, that changes the decision. You can explore the full range of licensed weight-loss options on our treatment overview page, which sets out what is currently available through a private prescription in the UK.

It is worth knowing that cost varies by dose and by what a provider includes in their price. If you are comparing options, our Wegovy cost guide explains what a legitimate private prescription should include and what questions to ask. That said, price is the wrong primary test for a prescription medicine, clinical suitability and supply-chain legitimacy matter more.

When semaglutide may not be the right fit

No licensed medicine suits everyone. Semaglutide is not recommended during pregnancy, breastfeeding, or if you are trying to conceive. It is not licensed for under-18s. Certain medical histories (including a personal or family history of medullary thyroid carcinoma or pancreatitis) require careful prescriber assessment before starting. These are not minor footnotes; a thorough clinical review exists precisely to work through them.

Tirzepatide (Mounjaro), a dual GIP and GLP-1 receptor agonist, produced greater average weight reduction than semaglutide 2.4 mg in the SURMOUNT-5 head-to-head trial published in 2025. For some patients that margin is clinically meaningful; for others, moving from semaglutide 2 to a dose they tolerate well may be the better practical choice. A prescriber can help weigh those factors against your health profile, not just the headline percentages. If you would like to speak with our clinical team before deciding, the FAQs cover the most common questions, or you can reach us directly through our contact page.

Semaglutide's efficacy record is genuinely strong. Whether that record applies to you is a clinical question, and our page on semaglutide 3 explains how our prescribers are well placed to answer it. Speak to our prescribers through a free consultation to find out whether you are suitable and which treatment fits your circumstances.