Using the Wegovy FlexTouch pen: what the evidence says and how it works in practice

What STEP 1 data tells us about semaglutide delivered this way

The evidence base for Wegovy begins with the STEP 1 trial, 68 weeks, once-weekly subcutaneous semaglutide 2.4 mg versus placebo in adults with obesity, published in the New England Journal of Medicine. Participants who received semaglutide lost an average of around 15% of their body weight. That figure comes from the titrated maintenance dose reached by the same step-wise schedule the FlexTouch pen is designed to deliver, start low, increase gradually, let the body adjust before moving to the next level.

What the trial also showed is that the slower you rise through the dose steps, the better tolerated the treatment tends to be. Nausea and other gastrointestinal effects, which are the most commonly reported side effects, were generally most noticeable in the first few weeks after a dose increase and eased as the body settled. That pattern is built into the pen's design logic: the 0.25 mg starting strength is there specifically to let your system find its footing, not to produce weight loss at week one.

There is a common assumption that the starter pen is somehow weaker or inferior. It isn't. It is doing a different job, reducing the chance that the first few weeks put you off a treatment that, given time, may work well for you. The NHS semaglutide medicine guide confirms this graduated approach as standard practice.

The FlexTouch pen: how an injection actually goes

The pen arrives pre-filled with one dose of semaglutide at its labelled strength. There is no cartridge to load and no separate needle to prime before you start. Before your first injection in a new pen, check that the liquid in the window is clear and colourless (a faint yellow tint is normal; cloudiness or visible particles is not). Wipe the injection site with an alcohol swab and let the skin dry completely before you proceed, this takes only a few seconds, but it matters.

Remove the pen cap. Place the pen tip flat against the skin at roughly a 90-degree angle. Press the injection button and hold it down until the dose counter reads zero, then keep the pen in place for a slow count of six seconds before lifting it away. That pause is the step most people skip the first time, and it is the step that makes the difference to whether the full dose is delivered. The used pen goes into a sharps container, standard household bins are not appropriate for used injection devices.

If you have questions about specific injection steps for your strength of pen, the Patient Information Leaflet inside the box is the definitive reference; it is written for your exact pen, not a general description. Your prescriber or pharmacist is also the right person to ask before your first use.

Rotating injection sites and managing the skin over time

Semaglutide is injected just under the skin (subcutaneously) rather than into muscle. The three approved sites are the abdomen (avoiding the two-inch area around the navel), the outer thigh and the upper arm. Each is equally effective. What changes the experience is whether you rotate systematically.

Injecting repeatedly into the same small patch of tissue can cause lipohypertrophy, a thickening that both feels uncomfortable and can affect how reliably the medicine absorbs, which is one reason our semaglutide injection bottle guidance covers storage and handling alongside site rotation. A practical approach is to divide each site into sections and move around them week by week. Abdomen one week, outer thigh the next, upper arm the week after: the specific pattern matters less than the consistency. If you are also using the semaglutide injection on the same day as another subcutaneous medicine, the NHS England weight-management injections guidance advises using different sites for each.

You can read more about the broader Wegovy injection format on our Wegovy pen overview page, or find detailed guidance on using the Wegovy FlexPen if that is the device supplied with your prescription. For a breakdown of what each pen contains in terms of volume and concentration, our Wegovy pen ml guide covers the main figures clearly. For a breakdown of what private semaglutide treatment typically costs, the Wegovy cost page covers the main factors without inflating expectations.

Side effects to recognise and when to seek help

The most frequently reported effects with semaglutide are gastrointestinal: nausea, loose stools, constipation, indigestion and, less commonly, vomiting. These tend to cluster in the days after starting or increasing the dose. Most people find they settle within a fortnight. Eating smaller portions, avoiding fatty or very rich food and staying well hydrated helps many people through the adjustment period.

A smaller number of people experience injection-site redness or mild swelling; rotating sites as above reduces this risk. More rarely, headache, fatigue and dizziness are reported, usually early in treatment.

Some symptoms need prompt medical attention rather than waiting to see if they settle. Severe abdominal pain that extends to the back (with or without vomiting) may indicate pancreatitis, a known but uncommon serious effect. The MHRA has highlighted this in safety communications for GLP-1 medicines; if you develop this symptom, stop the injection and get medical advice the same day. Gallbladder symptoms (sudden upper abdominal pain, especially after eating), signs of dehydration from prolonged vomiting or diarrhoea, or any sign of a serious allergic reaction (swelling, difficulty breathing, rapid heartbeat) all require urgent assessment.

Suspected side effects can be reported directly to the MHRA at Yellow Card. If you have concerns about your treatment that aren't covered in the leaflet, our prescribers offer 7-day aftercare, you can reach us through the contact page.

If you are considering starting semaglutide for weight management and want to understand whether it is clinically suitable for you, our Wegovy 1 pen page explains what the introductory supply includes before you start your free consultation with our GPhC-registered prescribers today.