What Are Semaglutide Injections — and How Do They Work?

Step 1, your prescriber establishes whether semaglutide is right for you

Before a single injection is given, a clinical assessment takes place. That is not a formality; it shapes every part of what follows. A GPhC-registered Independent Prescriber reviews your health history, current medicines, BMI, and any weight-related conditions. The licensed eligibility criteria for Wegovy are adults with a BMI of 30 or above, or 27 to 29.9 alongside at least one condition such as high blood pressure, high cholesterol, or obstructive sleep apnoea, though BMI alone never decides the outcome. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance.

One misconception that surfaces regularly is that semaglutide injections are essentially the same as Ozempic and can be swapped freely. If you want a clear answer to that question, reading about what Wegovy injections actually are helps set out the differences in dose, licence, and clinical oversight that make them quite distinct. Using a diabetes medicine for weight loss (or sourcing either without a prescription) sits outside the licensed framework and removes the safety net that a prescriber provides. Worth knowing before you go any further.

At nume, every new patient goes through photo-ID verification and live weight confirmation on video before a prescription is issued. Nothing is automated. You can read more on the frequently asked questions page if you want to understand what that process looks like day to day.

Step 2, the dose-escalation schedule and what it is designed to do

Wegovy begins at 0.25 mg weekly. That starter dose is not the one that drives weight loss, its job is to let your body adjust gradually, keeping side effects manageable. The schedule then steps up, roughly every four weeks, through 0.5 mg, 1.0 mg, and 1.7 mg before reaching the 2.4 mg maintenance dose. A higher 7.2 mg dose, approved by the MHRA in January 2026 and available as a dedicated single-dose pen from April 2026, is now the maximum licensed dose for adults with a BMI of 30 or above.

Each step is set by your prescriber. How quickly you move through them depends on how your body responds, it is never a fixed calendar. The clinical evidence for the 2.4 mg maintenance dose is substantial: the STEP 1 trial, published in the New England Journal of Medicine, reported an average body-weight reduction of around 15% over 68 weeks in adults with obesity who did not have type 2 diabetes. A useful overview of the broader semaglutide injection landscape covers how these figures sit within the wider treatment picture.

The practical side of injecting is straightforward once shown: the pen is pre-filled, the needle attaches and is changed with each dose, and the injection goes into the abdomen, thigh, or upper arm. Rotating the site each week is recommended. Storage is in the fridge at 2–8°C; there is a limited window for room-temperature use, but the Patient Information Leaflet gives the exact figures, always check there rather than relying on a third-party source.

Step 3, managing side effects and knowing when to call for help

The most common side effects are gastrointestinal: nausea, loose stools, constipation, indigestion, and sometimes vomiting. These tend to peak in the first week or two after starting or stepping up, and they ease for most people once the dose settles. Eating smaller portions, staying well-hydrated, and avoiding very fatty meals helps. How to take semaglutide injections has practical guidance on technique and timing that many patients find useful early on.

Some side effects require prompt medical attention. Severe stomach pain that spreads to the back (with or without vomiting) can be a sign of pancreatitis, which the MHRA highlighted in a Drug Safety Update in January 2026 as an infrequent but potentially serious complication of GLP-1 medicines. Symptoms of a gallbladder problem, signs of a serious allergic reaction, or significant dehydration following prolonged sickness also warrant contacting a doctor or going to A&E rather than waiting. The MHRA Yellow Card scheme lets patients report suspected side effects directly, which contributes to ongoing safety monitoring.

Semaglutide injections are not recommended during pregnancy, while breastfeeding, or when trying to conceive. They are not licensed for anyone under 18. If you take an oral contraceptive pill, discuss this with your prescriber before starting, there is some evidence that absorption may be affected, and an alternative method may be advisable during certain periods of treatment.

Getting a legitimate prescription in the UK

Because Wegovy is a prescription-only medicine, the only legal route to it is through a regulated prescriber and a GPhC-registered pharmacy. That point matters because the market for these medicines has attracted counterfeit products: the MHRA has seized large quantities of fake weight-loss pens sold without a prescription through social media, some containing insulin rather than semaglutide. Verifying any online pharmacy on the GPhC register takes less than a minute and is the simplest safety check available.

If you are considering private treatment and want to understand the cost side, the weight-loss treatments page sets out what is included in a private prescription service. A separate page exploring where to buy Wegovy in the UK covers what to look for in a provider. For those curious about how the Wegovy pen looks and operates before committing, pen images and device information are available too.

If you have questions about whether semaglutide injections are suitable for you, starting a free consultation with our prescribers is the right next step. The assessment is thorough, reviewed the same day by a real clinician, and there is no obligation to proceed.