How to use semaglutide for weight loss: what to expect, week by week

How exactly is a semaglutide injection given, and where?

The injection goes just beneath the skin (subcutaneously) rather than into a muscle. The three approved sites are the abdomen (at least a few centimetres from the navel), the front of the thigh, or the upper arm. Rotating between sites each week reduces the risk of localised skin reactions at any one spot.

Before you inject, clean the chosen area with an alcohol swab and allow it to dry. Pinch a small fold of skin, insert the needle at roughly a 90-degree angle, press the dose button and hold it in place for a few seconds before withdrawing. Wegovy comes as a pre-filled pen, so there is no drawing up of fluid and no manual needle attachment on the pen itself, the mechanism is self-contained. Always use a fresh needle for each injection and dispose of it safely in an approved sharps container; never recap and bin loose needles.

For the step-by-step process in full, the NHS medicines page for semaglutide and the Patient Information Leaflet inside your pack are the authoritative references. If anything about the injection technique feels unclear after reading them, speak to your prescriber or a pharmacist before your next dose.

Timing is flexible within the week. If you normally inject on a Monday and need to move it, you can shift by a day or two, as long as there is at least 48 hours between doses. You don't need to stick to a specific time of day, and the injection can be given with or without food.

What does the dose schedule actually involve over the first year?

The titration schedule for Wegovy is deliberate, not bureaucratic. Starting at 0.25 mg for the first four weeks gives your digestive system time to adjust before any meaningful appetite suppression begins. The 0.25 mg dose is not a therapeutic weight-loss dose, its job is to minimise early nausea so you can reach the doses that actually do the work.

From there, your prescriber increases the dose roughly every four weeks: 0.5 mg, then 1.0 mg, then 1.7 mg, then 2.4 mg maintenance. The MHRA also approved a 7.2 mg maintenance dose in 2026 for eligible patients, available as a dedicated single-dose pen. Whether any particular dose is right for you at any given time is a prescriber decision, titration is not automatic, and a dose increase at nume requires a clinical review of how you're getting on.

The STEP 1 trial, published in the New England Journal of Medicine, found that adults using semaglutide 2.4 mg alongside lifestyle changes achieved an average body-weight reduction of around 15% over 68 weeks. That figure comes from a clinical trial setting; individual results vary. More on what the evidence says about semaglutide injections is covered in our dedicated overview, including how results compare across doses and populations.

If you're transferring from another provider or have already been using semaglutide, your current dose can usually be continued rather than restarted from the beginning, subject to a clinical review and evidence of your current treatment history.

What side effects should you watch for, and when is something serious?

Nausea is the most frequently reported side effect, followed by loose stools, constipation, indigestion, burping and occasionally vomiting. For most people these are mild to moderate and are most noticeable after starting treatment or stepping up to a new dose, settling within days to a couple of weeks. Eating smaller, lower-fat meals and staying well hydrated tends to help.

A smaller number of people experience fatigue, headache or dizziness, particularly early on. Injection-site reactions (mild redness or discomfort where you inject) are also possible and usually resolve quickly.

Some symptoms do need prompt medical attention. Severe, persistent abdominal pain that radiates to the back, with or without vomiting, may indicate acute pancreatitis, seek urgent help if this occurs. The MHRA highlighted acute pancreatitis as a known but infrequent serious risk in a Drug Safety Update issued in January 2026. Other symptoms requiring urgent assessment include signs of a serious allergic reaction, significant dehydration from prolonged vomiting or diarrhoea, or gallbladder pain. You can report any suspected side effect through the MHRA's Yellow Card scheme, and our aftercare team is available seven days a week if you're unsure whether something needs attention.

For a fuller picture of the safety profile, our guide to semaglutide injection safety covers the evidence in more detail, including the contraception and surgery considerations that patients sometimes miss.

What does good use of semaglutide look like beyond the injection itself?

The medicine works best alongside a reduced-calorie diet and regular physical activity, not because this is a condition attached to the prescription, but because the appetite reduction semaglutide produces is most effective when it's paired with habits that reinforce it. Your appetite will genuinely fall; using that window to build sustainable eating patterns is where the long-term benefit comes from.

Protein intake deserves specific attention. Reduced appetite can lead to eating less protein than your body needs to preserve muscle mass, particularly if your total calorie intake drops sharply. Your prescriber or a dietitian can advise on practical targets for your circumstances.

Storage matters too. Wegovy pens should be kept refrigerated between 2°C and 8°C until use; refer to the Patient Information Leaflet for the exact window during which a pen can be kept at room temperature. If you're planning to travel, our guide to travelling with semaglutide covers what to prepare. Also worth knowing: semaglutide slows gastric emptying, which can affect how other oral medicines are absorbed, let any prescriber or GP know you're on it, and this is especially relevant for oral contraceptives, where the semaglutide pen overview has more background.

If you'd like to discuss how to use semaglutide for weight loss in the context of your own health, or want the full walkthrough of how to take Wegovy for weight loss, including practical tips on timing, technique and what to expect at each dose stage, our prescribers are available for a free consultation.