The Semaglutide Injection Explained: How It Works and What to Expect

Is the injection format right for you, or is there now an alternative?

This is a genuine fork in the road, not a rhetorical question. Until June 2026, semaglutide for weight loss in the UK came only as a weekly injection. That changed when the MHRA approved Wegovy tablets (the first oral GLP-1 medicine licensed for weight management in the UK) making it the first country in Europe to do so. Both forms contain semaglutide; the clinical difference is in how the drug reaches your bloodstream.

The injection delivers semaglutide directly into subcutaneous tissue, where absorption is consistent and largely unaffected by food, timing or other medicines. The tablet requires very specific conditions to work: taken first thing in the morning on an empty stomach with only a small amount of plain water, at least 30 minutes before eating, drinking coffee or taking any other oral medicines. For some people, that daily morning discipline is simple. For others (especially those with variable early schedules) the once-weekly injection asks less of daily routine.

If needles are the concern rather than daily logistics, it is worth knowing that the Wegovy pen uses a short, fine needle designed for the fatty layer just under the skin, not a muscle. Many people who were apprehensive find the reality much less troubling than the anticipation. Our full step-by-step guide to injecting semaglutide walks through the process in plain terms. For those who have already decided that tablets suit them better, the oral semaglutide option is covered separately.

Who the semaglutide injection is licensed for in the UK

The licensed criteria matter practically, because a prescriber works from them. Under the UK licence, Wegovy is approved for adults with a BMI of 30 or above, or a BMI of 27 to 29.9 alongside at least one weight-related condition, for example, high blood pressure, high cholesterol, type 2 diabetes, obstructive sleep apnoea or prediabetes. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance, reflecting different metabolic risk profiles. BMI is the starting point for a prescriber, not the whole picture.

The licence does not cover people who are pregnant, breastfeeding or actively trying to conceive. It is not licensed for anyone under 18. Certain conditions (including a personal or family history of medullary thyroid carcinoma or MEN2, and a history of pancreatitis) require careful prescriber discussion before any GLP-1 treatment is considered. The NHS semaglutide medicine page sets out the contraindications in full, and a prescriber will go through these during your consultation.

On the NHS, access to Wegovy runs through specialist weight management services with long waiting lists, and NICE's recommendation (TA875) limits its use to a maximum of two years within those services. A private route through a regulated pharmacy means no referral and no waiting list, for people who meet the clinical criteria. If you want to understand how the two routes compare, the Wegovy treatment overview sets them out side by side. Cost context (what private treatment actually includes) is covered on the Wegovy cost page.

What happens when you inject semaglutide: the practical detail

Semaglutide is injected into subcutaneous tissue (the layer of fat beneath the skin) at one of three sites: the abdomen (at least a few centimetres away from the navel), the front of the thigh, or the back of the upper arm. Rotating sites each week reduces the chance of local skin irritation. The Wegovy pen is pre-filled, meaning there is no drawing up of liquid or manual assembly; you dial nothing. It is one press.

Before injecting, the skin should be clean and dry. Wiping with an alcohol swab and allowing it to dry fully is good practice. Inject on the same day each week; if you need to shift the day (because of a bank holiday, a planned trip, or simply because the Monday routine works better for you) you can move the day by up to a day or two without losing clinical effect, but confirm any changes with your prescriber. The pen must be stored in the fridge between uses; for the exact temperature range and any out-of-fridge window, the Patient Information Leaflet that comes with your medication is the definitive reference. Our page on storing your semaglutide injection covers the practical questions that come up most often.

Used needles and pens are sharps and must be disposed of in an approved sharps container, not in household bins. Your local pharmacy or GP surgery can advise on collection points.

Side effects to know before you start

The most commonly reported side effects are gastrointestinal: nausea, vomiting, diarrhoea, constipation and indigestion feature most often, particularly in the early weeks and after a dose increase. For most people they are mild to moderate and ease over time as the body adjusts. Going slowly on the escalation schedule (which is exactly why the schedule exists) keeps most of this manageable.

There are less common effects to be aware of. In January 2026, the MHRA issued a Drug Safety Update highlighting that acute pancreatitis, while infrequent, is a known risk with GLP-1 medicines: severe, persistent abdominal pain that radiates to the back, with or without vomiting, warrants prompt medical attention. Gallbladder-related symptoms, signs of an allergic reaction and significant dehydration from persistent vomiting are also reasons to contact a healthcare professional without delay. You can report any suspected side effect via the MHRA Yellow Card scheme.

Women using oral contraceptives alongside tirzepatide face a specific absorption consideration, but the NHS notes no equivalent evidence for that interaction with semaglutide. If you have questions about contraception, HRT or an upcoming surgical procedure while on semaglutide, raise them with your prescriber before starting. If you are curious whether semaglutide at a specific dose step might suit you, the 2 mg injection strength page gives context on where that fits in the titration journey. When you feel ready to find out whether you are clinically suitable, you can check your eligibility through a free consultation with our prescribers.