Semaglutide Step 1: What Does the 0.25mg Starting Dose Actually Do?

Why does the Wegovy programme begin at such a low dose?

Semaglutide works by activating GLP-1 receptors in the brain and gut, slowing how quickly the stomach empties and reducing the drive to eat. That mechanism is powerful, and it is precisely why the programme starts gently. Jumping straight to a high maintenance dose would be likely to cause significant nausea, vomiting and other gastrointestinal discomfort for most people.

The 0.25mg step exists to let the body build familiarity with the medicine. Think of it less as a treatment dose and more as an acclimatisation period. Most people find that any early side effects during step 1 are milder than what they might have experienced on a higher dose from the outset, and they often settle within the first week or two.

This is not unique to semaglutide. The same principle applies across the GLP-1 class, you can read more about how this medicine works on our semaglutide overview page. The full Wegovy titration pathway is covered in detail on the Wegovy treatment page.

What side effects are most common at step 1, and how long do they last?

Even at 0.25mg, some people notice nausea, loose stools, constipation, burping, or a general queasiness, particularly in the first few days after each injection. These are the most commonly reported effects during the starting phase and tend to be mild at this dose. Fatigue and headache appear for some people too.

The good news is that side effects at step 1 are usually at their most manageable of the entire programme, precisely because the dose is low. Most people find things settle considerably before they move to step 2 at 0.5mg. Eating smaller portions, staying well hydrated, and avoiding fatty or rich foods can help during the adjustment period, your prescriber can advise on practical strategies.

Severe or persistent abdominal pain that radiates to your back, with or without vomiting, is not a normal adjustment symptom, seek urgent medical attention if that occurs. Report any unexpected reactions to the MHRA via the Yellow Card scheme.

If you have questions about what you're experiencing, our support team is available seven days a week.

Who is the Wegovy titration schedule intended for, and does step 1 always last four weeks?

The licensed population for Wegovy in the UK is adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related health condition such as high blood pressure, raised cholesterol, or type 2 diabetes. BMI alone does not determine suitability, the full clinical picture matters, and a prescriber reviews every case individually.

The standard instruction is to stay at each step for roughly four weeks before moving up. That timetable can be extended. If someone is still experiencing side effects they find difficult to manage, the prescriber may recommend staying at 0.25mg for longer before advancing. The four-week minimum is a floor, not a ceiling. It is your prescriber, working with you, who decides when you are ready to move on, not a fixed calendar date.

Teenagers and anyone under 18 are not within the licensed population. Semaglutide is not recommended during pregnancy, while breastfeeding, or when trying to conceive. Our FAQs cover some of the most common eligibility questions.

How does step 1 connect to the rest of the Wegovy programme?

After completing step 1, the typical pathway moves through further fortnightly or monthly increases. Step 2 brings the dose to 0.5mg; subsequent steps climb through 1.0mg, then 1.7mg, before reaching the standard 2.4mg maintenance dose. A higher 7.2mg dose was approved by the MHRA in April 2026, available via a dedicated single-dose pen for adults with a BMI of 30 or above, titrated by a prescriber from the usual starting point.

The weight-loss effect builds across the programme. Most of the clinical benefit observed in trials (the STEP 1 trial published in the New England Journal of Medicine reported around 15% average body-weight reduction over 68 weeks at the 2.4mg maintenance dose) accumulates after reaching and sustaining higher doses. Step 1 is the foundation. The progression through step 3 and beyond is where that effect develops.

If you are considering where you are in your own programme, or thinking about starting, the full semaglutide step guide gives a clear overview of the whole titration journey. For a sense of what private treatment involves from the beginning, our weight-loss treatment overview is a good starting point, and if you would like to understand how private pricing compares, the Wegovy price comparison page sets out what to look for.

When you feel ready to explore whether this is right for you, you are welcome to check your eligibility with our prescribers. Every consultation at nume is reviewed by a GPhC-registered Independent Prescriber, a real clinician reads your answers the same day.