Found a lump under the skin after a Wegovy injection?

You've pressed the cap, injected, and now there's a raised area where the needle went in, here's why

Picture what happens under the skin. Wegovy is delivered into subcutaneous fat, the soft layer between skin and muscle. When the injection goes in correctly, the medicine disperses gradually through that fat. When it doesn't (because the needle was inserted at too shallow an angle, because the skin wasn't pinched to gather enough tissue, or because the same spot has been used week after week) the fluid has nowhere to spread. It stays put, forming a small nodule that your fingers can feel and, sometimes, your eye can see.

The medical term is a localised injection-site reaction. Semaglutide isn't irritating fat in the way some older injectable medicines can be, so the lump is usually caused by technique or site-rotation issues rather than the medicine itself. The NHS semaglutide medicines page lists injection-site reactions among the recognised side effects of weekly semaglutide injections, classing them as common but not dangerous in the usual presentation.

Some people find the lump is mildly tender when pressed. Others feel nothing at all and only notice it by touch. Either way, the body absorbs the pooled medicine over the following days, and the nodule shrinks. If you notice a fluid-filled bubble under the skin after your Wegovy injection, that specific presentation has its own causes and is worth reading about separately. If you're wondering whether what you can feel is truly a lump from the injection or something else, our dedicated guide to lumps after injecting Wegovy walks through the distinctions.

Is this lump normal, or does it need a doctor's attention?

Most injection-site lumps sit neatly in the 'expected and resolving' category. The skin over the area may look slightly raised or faintly pink for a day or two. The lump itself is firm-ish, roughly pea-sized or smaller, and sits right where the needle went in. It doesn't spread. It doesn't get hotter. Within three to seven days it's gone.

The signs that push a lump out of that normal range are worth memorising. Seek medical help if the lump is growing rather than shrinking after two or three days, if the surrounding skin is distinctly red and warm to the touch, if you develop a fever, or if you see any discharge from the injection site. These could indicate a skin infection (abscess), which is uncommon but needs antibiotic treatment. A severe allergic reaction (widespread rash, swelling of the lips or throat, difficulty breathing) is rare but an emergency; call 999.

For anything that sits in the middle ground (a lump that's just taking longer than expected to go, or tenderness that's distracting) your prescriber is the right first call. You can also reach our clinical support team, who are available seven days a week.

Technique adjustments that make a real difference

The single most effective fix is consistent site rotation. Wegovy's licensed injection sites are the abdomen, the outer thigh, and the upper arm. Each of those areas has enough surface to give you multiple sub-sites, think of the abdomen as a clock face and move around it. Never inject into the same spot two weeks running. If you've been jabbing the same patch of belly through busy patches (the fortnight before Christmas, a holiday week, a Monday when you're just getting it done) the fat there can become slightly thickened, which makes pooling more likely.

Depth matters too. The needle should enter at roughly a 90-degree angle if you have a reasonable amount of subcutaneous tissue, or at 45 degrees if you're leaner. Pinching the skin first gathers enough fat to ensure you're not hitting muscle, which causes more discomfort, or sitting too shallow, which causes pooling. Our page on whether to pinch the skin for a Wegovy injection covers this in practical detail. Injecting slowly (taking a full ten seconds rather than rushing the plunger) also helps the medicine disperse rather than pool.

Needle cleanliness matters. A fresh needle tip is fractionally sharper and causes less micro-trauma to the tissue; a blunted tip from a previous use drags through fat and can trigger a stronger local reaction. Cleaning the site beforehand with an alcohol swab removes surface bacteria and reduces the risk of any localised infection. These small steps compound over months of weekly injections.

When site reactions are a recurring problem, bring it up at your next review

The occasional lump after a single injection is very different from getting one every week. If you're finding that nearly every dose leaves a nodule that takes longer than a few days to settle, that pattern is worth flagging. It could point to a consistent technique issue (something a prescriber or nurse can usually sort quickly) or, less commonly, to a localised hypersensitivity that might influence which injection sites work best for you.

A small subset of people find the abdomen reacts more than the thigh, or vice versa, and simply switching primary site resolves it. For a fuller picture of how semaglutide behaves at the injection site and what the research shows, see the evidence on semaglutide injection-site reactions.

It's also reasonable to raise injection-site reactions at any consultation review. At nume, every repeat order goes through a fresh clinical assessment by a GPhC-registered prescriber, a real clinician reading your update, not an automated pass-through. If you haven't started treatment yet and want that kind of oversight built in from the start, the consultation page is the place to begin. If cost has been part of your thinking, our Wegovy cost breakdown sets out exactly what's included in a private prescription through a registered pharmacy. The NHS England guidance on weight-management injections also has practical advice on injection technique alongside the clinical eligibility information.