What to expect on day 1 of Wegovy: the truth before you inject

The biggest myth: you'll feel different straight away

A common expectation walking into day 1 of Wegovy is that hunger will vanish or the scales will shift by morning. Neither is likely, and believing otherwise sets people up for unnecessary doubt about whether the treatment is working.

Semaglutide acts on GLP-1 receptors to slow gastric emptying and signal fullness to the brain, but those effects build gradually as the dose escalates over several months. The 0.25 mg starting dose keeps side-effect risk low during the adjustment period; the timeline for meaningful weight change runs across weeks and months, not hours. The STEP 1 trial, published in the New England Journal of Medicine, recorded an average body-weight reduction of around 15%, but that was measured at 68 weeks on the 2.4 mg maintenance dose, not on day one at a fraction of that amount.

Resetting that expectation is not pessimism. It is the foundation for staying with treatment long enough for it to work. Plenty of people inject their first dose, feel almost nothing, and wonder if something went wrong. Nothing did. Your body simply hasn't had time to notice yet.

What you may genuinely feel in the first 24 hours

Some people do experience side effects on day 1, and it is worth knowing what they feel like so they don't come as a surprise. The most frequently reported are gastrointestinal: mild nausea, a sense of fullness that arrives sooner than usual at meals, loose stools or constipation, and occasional belching or indigestion. Fatigue and a mild headache are also reported by some people in the first day or two. Week 1 of Wegovy tends to be when these early effects are most noticeable, if they appear at all.

For most people, these sensations are genuinely mild. Eating a smaller, lower-fat meal before or after the injection, staying hydrated, and not lying down immediately after eating all help. If nausea is more than mild or is accompanied by severe, persistent stomach pain (particularly pain that radiates toward the back) that warrants prompt medical attention. The NHS semaglutide information page lists the full side-effect profile and sets out when to seek urgent help, and the MHRA's Yellow Card scheme at yellowcard.mhra.gov.uk is the right place to report anything unexpected.

One practical tip our prescribers mention regularly: keep the pen in the fridge door (somewhere you'll see it each week) and pair the injection with an existing routine, like the evening before your quietest morning, so the timing becomes automatic rather than a thing to remember.

The injection itself: what the process actually looks like

Wegovy comes as a pre-filled pen. You select the injection site (abdomen, thigh or outer upper arm) clean the skin with a swab, press the pen firmly against it, and hold for several seconds until the injection is complete. The needle retracts automatically. Most people describe the sensation as a brief pinch; the device is designed to make technique straightforward even if you have never self-injected before.

If you are looking at the practicalities of starting, the step-by-step guide to your first Wegovy day covers the injection process in more detail. Used needles must be disposed of in an approved sharps container, never in household waste. Rotate injection sites each week to reduce localised irritation.

For context on how the first injection fits into the broader arc of treatment, what to expect from Wegovy overall maps the dose escalation journey from 0.25 mg through to the maintenance dose. And if you want to look further ahead, week 5 is typically when the first dose increase arrives, which is when many people notice the treatment starting to feel different.

Getting here: how Wegovy reaches you through a licensed prescriber

Wegovy is a prescription-only medicine. That means day 1 only happens after a qualified prescriber has reviewed your medical history, confirmed your eligibility, and issued a prescription, the same as any other POM. At nume, that review is carried out by a GPhC-registered Independent Prescriber, a real clinician reading your answers rather than automated software, typically on the same day you complete your consultation. Order before 12pm on a working day and, once clinically approved, your treatment is dispatched the same day with free next-working-day DPD delivery in plain packaging.

For anyone considering the treatment but unsure about costs, the Wegovy pricing and access page sets out what a private prescription involves and what the transparent price at nume includes. Wegovy is a prescription-only medicine; eligibility is determined by clinical assessment, not by BMI alone. If you have already decided you want to explore starting treatment, you can check your eligibility with our prescribers at any point.