When should I start Wegovy, and how do you know you're ready?

What the STEP 1 trial tells us about who responds, and when

The question of when you should start Wegovy is partly about timing and partly about suitability. The STEP 1 trial, published in the New England Journal of Medicine, followed 1,961 adults with obesity over 68 weeks and found an average body-weight reduction of around 15% among those on 2.4mg semaglutide alongside a reduced-calorie diet and increased physical activity. Those results came from people who met strict enrolment criteria: a BMI of 30 or above, or 27 or above with a qualifying condition, no personal history of type 2 diabetes, and genuine engagement with the lifestyle programme running alongside the injections. That profile matters because Wegovy works within a framework, not instead of one. Starting before that framework is in place, or before contraindications have been checked, risks both safety and outcome.

The licensed dose escalation reflects this: treatment opens at 0.25mg weekly for four weeks, then moves through 0.5mg, 1.0mg and 1.7mg before reaching the 2.4mg maintenance dose, with roughly four weeks at each level. Your first injection is a tolerability phase. Most people find the gradual climb keeps gastrointestinal side effects manageable. When Wegovy starts working is a separate question from when you start it; if you're wondering when you should start losing weight on Wegovy, measurable weight change typically becomes visible several weeks in, once you're on a therapeutic dose.

Reading the NICE criteria: who this medicine is actually for

NICE's recommendation for semaglutide (TA875) sets out the population it should be used in: adults with a BMI of 35 or above and at least one weight-related comorbidity, within a specialist weight management service, for a maximum of two years. Lower thresholds of around 32.5 apply for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds. The private licensed criteria are somewhat broader (the SmPC covers BMI 30 or above) but the principle holds: a prescriber uses the full clinical picture, not a single number.

NICE also specifies a review point: if a patient has lost less than 5% of their body weight after six months at the maintenance dose, the decision to continue should be reconsidered. That is not a failure clause; it is a safety net ensuring the medicine's risks are only carried when there is meaningful benefit. When to stop Wegovy is a conversation your prescriber should open at that point, not one you should navigate alone. The NICE appraisal of semaglutide is publicly available and worth reading if you want to understand how the committee weighed the evidence.

Situations that affect the starting decision

Several personal circumstances change whether now is the right time to start. Wegovy is not recommended during pregnancy, breastfeeding, or if you are actively trying to conceive; the MHRA advises using effective contraception during treatment and for a period afterwards before attempting conception. Women using oral contraceptives alongside semaglutide should discuss this with their prescriber, since GLP-1 medicines can affect gut transit and theoretically the absorption of oral medicines, though the interaction evidence for semaglutide specifically is less pronounced than for tirzepatide.

A personal or family history of medullary thyroid carcinoma, MEN2 syndrome, or previous pancreatitis will all feature in your assessment. So will recent surgery, or surgery that's planned: anaesthetists need to know you are on this class of medicine before any procedure. None of this means those situations are automatic barriers, but they are reasons the starting decision belongs with a prescriber rather than a website. If you want to understand the broader treatment landscape before your consultation, including what Wegovy is called across different markets and formulations, the Wegovy overview covers the mechanism, the schedule and what the evidence shows.

Practical readiness: timing the start around your life

Beyond clinical eligibility, there is a practical dimension to when you start that our prescribers hear about most weeks. The first few weeks at a new dose sometimes bring mild nausea, and some people prefer to begin on a quieter patch — not mid-holiday, not during an unusually demanding stretch at work. That is a personal call, not a medical requirement, but it is sensible planning. Storage is straightforward: the pen lives in the fridge, ideally somewhere you'll see it weekly, alongside everyday items rather than tucked behind something you move each time. Consistency helps.

On the financial side, private Wegovy treatment is a monthly cost that varies by dose and provider. A useful overview of what those costs cover, and why transparent pricing matters for a prescription medicine, is on the treatment options page. There are no NHS waiting-list shortcuts here: Wegovy is available on the NHS only through specialist services under TA875, and access is genuinely limited. For people who do not want to wait, or who fall outside the NHS thresholds, a regulated private clinic with a GPhC-registered prescriber is the legal alternative.

If you are still uncertain whether Wegovy or another licensed treatment is the right fit, our weight-loss overview sets out the options side by side. And if you're ready to find out whether you're clinically suitable, speaking to our prescribers is the practical next step, a free consultation, reviewed the same day by a real clinician.