What Are Wegovy Injections and How Do They Work?

What the trial evidence showed, and what it means in practice

The STEP 1 trial enrolled almost 2,000 adults with obesity or overweight and at least one weight-related condition. Over 68 weeks, those using semaglutide 2.4mg alongside a reduced-calorie diet and increased activity lost an average of around 15% of body weight, compared with roughly 2.4% in the placebo group. That is a meaningful difference, and it is why the NICE appraisal of semaglutide (TA875) recommended the medicine for use in certain NHS settings.

There is a misconception worth clearing up gently: Wegovy is sometimes described as a quick fix or a shortcut. The trial evidence points the other way. Weight loss was gradual, building over months as doses increased, and the lifestyle component (eating and activity habits) ran alongside treatment throughout. The injection does not override biology; it works with it, reducing the hunger signals that make sustained dietary change so difficult for many people.

A higher 7.2mg maintenance dose, approved by the MHRA in early 2026, reported average weight loss of around 20.7% over 72 weeks in trials, narrowing the gap with tirzepatide results. If you want to explore how the two medicines compare, the weight-loss treatment overview sets that out clearly.

How a Wegovy injection is actually given

Each Wegovy pen comes pre-filled and pre-set to the correct dose for that stage of treatment. You inject subcutaneously (just beneath the skin) into the abdomen, thigh, or upper arm, rotating the site each week to avoid irritation. The needle is fine and covered; most people find the process straightforward after the first injection. For detail on how frequently doses change and what the schedule looks like week to week, the Wegovy injection frequency page covers that in full.

Storage matters. Pens should be kept refrigerated between 2°C and 8°C; the exact room-temperature window for a pen that has been removed from the fridge is specified in the Patient Information Leaflet and should be followed precisely rather than estimated. If you are using sharps at home, a proper sharps disposal container is the safe and legally correct way to dispose of used needles.

The NHS patient-level guidance on semaglutide at nhs.uk/medicines/semaglutide gives a plain-English overview of administration and what to do if a dose is missed, always a good first reference, alongside the leaflet in the box.

Side effects and when to seek help

The most common side effects with Wegovy injections are gastrointestinal: nausea, vomiting, diarrhoea, constipation, and indigestion are all reported, particularly after starting treatment or stepping up to the next dose. For most people they are mild to moderate and ease within a couple of weeks as the body adjusts. Fatigue, headache, and dizziness also appear in the reported data.

Pancreatitis is an infrequent but serious possibility. If you develop severe, persistent stomach pain that radiates towards the back (with or without vomiting) seek urgent medical attention. The full side-effects guide for Wegovy covers both the common and the rarer presentations, including what to monitor and what warrants a call rather than a wait-and-see.

Wegovy is not recommended during pregnancy, while breastfeeding, or when actively trying to conceive. It is not licensed for anyone under 18. People with a personal or family history of medullary thyroid carcinoma, or certain other conditions, need to discuss this with a prescriber before starting. These are not reasons to avoid asking, they are exactly the kind of detail a clinical consultation is designed to work through.

How Wegovy differs from Ozempic, and what that means for access

Ozempic also contains semaglutide and is made by the same manufacturer, Novo Nordisk. The two are not interchangeable from a licensing perspective: Ozempic is licensed for type 2 diabetes, not weight management, and prescribing it for weight loss sits outside its UK marketing authorisation. Wegovy is the correctly licensed option for weight management. Some people encounter the two names together online and assume they work identically for any purpose, they share an active ingredient, but licensing exists for good clinical reasons.

On the NHS, Wegovy is available through specialist weight management services under NICE TA875, though waiting lists are commonly long. Private prescriptions through a regulated online pharmacy offer an alternative for people who do not meet NHS thresholds or prefer not to wait. Whatever route you explore, the medicine is prescription-only and requires a clinical assessment. If you are weighing up the options, the Wegovy cost page explains what private treatment typically involves financially. Our clinical team reviews every consultation personally, the same day it is submitted, to assess whether Wegovy is appropriate for you.

To learn more about how the injections sit within the broader picture of semaglutide treatment, this overview of semaglutide injections adds useful context. When you are ready to speak to a prescriber, start your free consultation here.