Semaglutide 2.5 mg Dosing: What the Starting Dose Is Really For

Step 1: Identify which medicine the 2.5 mg figure belongs to

The mix-up is understandable. Both Wegovy and Mounjaro are once-weekly injections used for weight management in UK adults, both are GLP-1-related medicines, and both follow a slow titration approach. But their dose ladders are completely different.

Wegovy's schedule runs: 0.25 mg (weeks 1–4), 0.5 mg (weeks 5–8), 1.0 mg (weeks 9–12), 1.7 mg (weeks 13–16), then 2.4 mg as the standard maintenance dose. With the MHRA's 2026 approval of a 7.2 mg pen, the maximum has extended further for eligible patients, but 2.5 mg is not a step in this sequence at any point. The Wegovy overview page sets out the full licensed picture if you want more background on how semaglutide works.

Mounjaro (tirzepatide) begins at 2.5 mg for the first four weeks. That starting pen is explicitly a tolerability dose, its purpose is to let your body adjust to the medicine's effects before the dose climbs. The NHS medicines page for tirzepatide describes it the same way. So if you've read "2.5 mg" in a forum thread or product listing alongside semaglutide, the most likely explanation is that the posts or pages were conflating the two medicines.

Step 2: Understand why both schedules start low

Whether the medicine is semaglutide or tirzepatide, the slow start exists for the same practical reason: GLP-1 receptor agonists commonly cause nausea, vomiting or digestive discomfort, particularly in the early weeks. Rushing up the dose ladder increases that risk significantly.

For semaglutide specifically, the 0.25 mg starting dose produces modest appetite suppression. Most of the clinical weight-loss effect builds as the dose reaches 1.7 mg and 2.4 mg. The patient experience at different semaglutide doses reflects this, people frequently describe the lower rungs as a settling-in period rather than active treatment. That framing is accurate: the STEP 1 trial, published in the New England Journal of Medicine, recorded an average body-weight reduction of around 15% at 2.4 mg over 68 weeks, and those results were achieved at the maintenance dose, not the starting one.

Mounjaro's titration follows a similar logic. The 2.5 mg first pen doesn't produce significant weight loss on its own; the clinical effect accumulates as the dose climbs toward 10, 12.5 or 15 mg. For a side-by-side look at what the Wegovy dose ladder looks like across all steps, the Wegovy doses guide covers each stage in detail.

Step 3: Know what a prescriber assesses before any dose change

Neither titration schedule is something you manage alone. At each step (whether that's moving from 0.25 mg to 0.5 mg on semaglutide, or from 2.5 mg to 5 mg on tirzepatide) a prescriber reviews how you've tolerated the current dose, your weight progress, and any side effects before authorising the next pen.

At nume, a GPhC-registered Independent Prescriber personally reviews every repeat request. There's no automated sign-off. If a dose increase is due, our clinical team looks at the evidence, not just a tick-box form. That's worth understanding because some services automate this step in ways that bypass proper clinical judgement.

Common side effects across both medicines are gastrointestinal: nausea, loose stools, constipation, reflux, and fatigue are the most frequently reported, particularly in the first few weeks at a new dose. Symptoms usually settle, but if they don't (or if you develop severe stomach pain that extends to your back) that needs prompt medical attention, not a wait-and-see approach. The MHRA's Yellow Card scheme (yellowcard.mhra.gov.uk) is where side effects from either medicine can be reported.

Keeping your pen in the fridge door at home and doing a quick check each week before your injection day is a simple habit that ensures you're not storing it incorrectly, both medicines require refrigeration between 2°C and 8°C, with a limited room-temperature window covered in the Patient Information Leaflet.

If you're thinking about costs before starting treatment, the Wegovy pricing page sets out what private prescriptions typically involve in the UK.

Step 4: Make sense of what you actually need from here

If your search for "semaglutide 2.5 mg dosing" was really a question about Mounjaro's starting dose, the 2.5 mg dose page addresses that context directly, though it's worth bookmarking the distinction that the medicine involved is tirzepatide, not semaglutide.

If you're already on Wegovy and trying to understand where you are in the schedule, the maintenance dosing guide for semaglutide explains what happens once you reach 2.4 mg and what factors affect whether a prescriber might consider the higher 7.2 mg option.

And if you're at the stage of deciding whether semaglutide or tirzepatide is the right starting point for you, that's a clinical conversation. Our weight-loss treatment overview explains both options factually, and a prescriber at nume can assess which is appropriate for your situation. Speak to our prescribers through a free consultation at our treatment page, it's the same-day, clinician-led review that determines whether either medicine is right for you, not a form processed by software.