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Wegovy injections: how they work, the science, and dose titration
- Jul 16
- 3 min read
Wegovy (Semaglutide) was one of the first GLP-1 medications licensed for weight management in the UK, and it remains one of the most established options we prescribe. Here's what's actually happening in the body when you take it, what the trial evidence shows, and what the dose titration schedule looks like in practice.
How Wegovy works
Semaglutide is a GLP-1 receptor agonist. Unlike Mounjaro, which acts on two hormone pathways, Wegovy copies a single natural gut hormone called glucagon-like peptide-1 (GLP-1), released after eating. That one pathway has a broad effect on appetite and digestion, which is why a single-pathway medication can still produce substantial results.
Slower stomach emptying. Food stays in the stomach for longer, extending how long a meal keeps you feeling full.
Steadier blood sugar. GLP-1 helps release insulin when it's needed and suppresses the hormone that tells your liver to release extra glucose, smoothing out the spikes and dips that drive cravings.
Reduced hunger signals. GLP-1 receptors in the brain's appetite centre reduce hunger and the urge to snack between meals.
What the trial evidence shows
Wegovy's licensing was based on the STEP 1 trial, a 68-week study of adults with obesity who did not have diabetes. On the standard 2.4mg maintenance dose, participants lost an average of 14.9% of their body weight, compared with 2.4% in the group given a placebo alongside diet and lifestyle support. As with any medication, these are trial averages, and individual results vary.
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A newer, higher 7.2mg dose has since been studied in the STEP UP trial for people who need more than the standard dose achieves. Over 72 weeks, participants on 7.2mg lost an average of 20.7%, compared with 17.5% on the standard 2.4mg dose within the same trial. This is a separate, more recent trial, so the numbers aren't directly comparable to STEP 1 above, but it shows there's now a higher-dose option for those who need it.
Dose titration: what to expect
Wegovy is introduced gradually to allow the digestive system to adjust, which is the main reason side effects tend to be far milder than people anticipate.
The standard schedule looks like this:
Weeks | Dose |
1–4 | 0.25mg (starting dose, not yet at a treatment level) |
5–8 | 0.5mg |
9–12 | 1mg |
13–16 | 1.7mg |
17+ | 2.4mg (standard maintenance dose) |
Each step is usually held for at least four weeks, so reaching the standard maintenance dose takes around 16 weeks in total. Not everyone needs or wants to go up to 2.4mg, plenty of people reach their goals comfortably at the standard dose, Our Clinical Team will advise the dose that is best for you.
Common side effects during escalation
The most frequently reported side effects are gastrointestinal: nausea, diarrhoea, constipation and occasional vomiting. These usually cluster around dose increases and settle within a week or two. Eating smaller, less fatty meals around a dose change, eating more slowly, and staying hydrated all tend to help.
The bottom line
Wegovy works by copying a single gut hormone that slows digestion, steadies blood sugar and quietens appetite, and the step-by-step dosing is designed to get you there as comfortably as possible. If you're deciding whether it's the right option for you, our clinical team can talk through your history, goals and the titration plan in detail.
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