What happens if you inject Wegovy into a stretch mark?

You've spotted a stretch mark and you're holding the pen, here's what that actually means

Stretch marks form when the skin stretches faster than the deeper dermis can keep pace with, leaving bands of fibrous scar tissue just below the surface. That texture you can feel (and sometimes see as raised or indented lines) reflects a structural change in the tissue itself. Subcutaneous fat, the soft layer directly under the skin, is where Wegovy is designed to be delivered. In areas of significant scarring, that soft-tissue layer is interrupted or compressed by fibrous collagen, and it has a reduced blood supply compared with unscarred skin nearby.

When a Wegovy dose lands in or very close to that fibrous tissue rather than the intended subcutaneous layer, the semaglutide may not disperse as evenly or absorb as predictably. A single injection that clips the edge of a stretch mark is unlikely to cause a problem you'd notice. The concern is more about consistency: if you habitually return to the same marked area because it's convenient, you may get slightly variable drug levels over time, which is not what weekly dosing is designed to produce. It can also leave the site more irritated than it would otherwise be. The NHS patient information for semaglutide recommends rotating sites each week precisely to protect the tissue and maintain reliable absorption.

The short answer to whether it's dangerous: no, not acutely. The more useful question is whether it's the best site available to you, and almost always, it isn't.

Which injection sites actually work, and how to find the right spot on your own body

Wegovy's licensed injection sites are the front of the thigh, the abdomen (keeping a couple of inches clear of the navel), and the outer upper arm. All three work because they typically carry a sufficient layer of subcutaneous fat for the medicine to distribute properly. A question our prescribers hear most weeks is how to rotate sensibly when stretch marks cover a large part of the abdomen or thighs, and the honest answer is that you have more usable surface area than you might think.

Within each site, aim for areas where the skin pinches easily between your fingers and feels soft underneath. Stretch marks don't necessarily disqualify an entire zone; a small cluster of marks in one part of your abdomen still leaves the rest of it available. The practice of pinching the skin before inserting the needle also helps confirm you're in subcutaneous tissue rather than muscle, a different type of injection error covered separately if you've ever wondered what happens if Wegovy is injected into muscle.

Spacing your injection points at least a centimetre apart from the previous week's site, and keeping clear of any visible marks or lumps, gives each area time to recover fully. Keeping a simple rotation note (even a rough sketch) takes the guesswork out of it. Clean the chosen spot with an alcohol swab beforehand; individually wrapped swabs are an easy way to keep a supply with your pen.

What the evidence says about site selection and absorption

Pharmacokinetic studies on subcutaneous semaglutide (the same molecule in Wegovy) confirm that the abdomen, thigh, and upper arm produce broadly comparable blood-level profiles when the injection is placed correctly in subcutaneous tissue. Scarred or lipohypertrophic areas (lumps from repeated injections in the same spot) are consistently flagged in prescribing guidance as sites to avoid, because the altered tissue changes the absorption profile. This is the same principle applied to insulin therapy, where avoiding scar tissue is a well-established part of patient education.

The concern is not that stretch marks are medically hazardous injection zones; it's that they represent suboptimal tissue. Clinical trial participants in the STEP programme (the trials underpinning Wegovy's licence, published in the New England Journal of Medicine) were given structured injection-site guidance and trained in rotation technique. Replicating that consistency at home is part of getting the most from treatment.

If you've already injected into a stretch mark and are worried, the realistic picture is reassuring: one or two instances are unlikely to have meaningfully affected your dose. What matters is building a rotation habit from here. For broader context on how semaglutide behaves in the body and what to expect from treatment, the overview of what happens when you take Wegovy walks through the pharmacology in plain language. And if you're still deciding whether this treatment is right for you, the weight-loss treatment overview covers the full landscape of options.

When to mention injection sites to your prescriber

Most people work out a comfortable rotation without needing to raise it at a review. But a few situations are worth flagging. If you notice persistent lumps, redness, or tenderness building up at a site, that's a sign the tissue needs longer to recover, and your prescriber can help you adjust the plan. If stretch marks cover such a wide area that you're genuinely struggling to find clear spots across all three licensed sites, that's also a conversation worth having; technique adjustments or a clearer rotation map can make a real difference.

It's also worth knowing that accidentally injecting Wegovy into a stretch mark once is a common experience, far more common than most people mention. You don't need to skip a dose or repeat the injection. Continue your normal schedule, and just aim for clearer tissue next time. If you're approaching the end of your course and wondering about the longer-term picture, our guide on what happens if you stop Wegovy explains what to expect when treatment ends, and a more detailed look at the physiological changes involved is covered in the page on what happens when you stop Wegovy, which is worth reading before making any decisions about pausing or finishing treatment.

At nume, every repeat supply is reviewed by a GPhC-registered prescriber before it's dispensed, not because it's a box-tick, but because questions like site rotation, tolerability and dose progression are genuinely worth checking in on. If you'd like to discuss your injection technique or find out whether Wegovy is a suitable option for you, check your eligibility with a free consultation.