What Happens When You've Injected Wegovy into a Stretch Mark

The misconception worth setting aside first

There's a worry that injecting into a stretch mark somehow wastes the dose or delivers it into the wrong tissue. It's an understandable concern — stretch marks look and feel different from surrounding skin, so it's natural to wonder whether the needle went somewhere it shouldn't. In practice, a stretch mark is a change to the dermis, the layer of skin that sits above the subcutaneous fat. The needle on a Wegovy pen is designed to reach that fat layer, which lies beneath the dermis regardless of whether a stretch mark is visible on the surface.

So the medicine almost certainly reached the right destination. That said, if the area felt unusual, or if you're seeing a reaction you don't recognise, it's always worth contacting your prescriber or calling 111. You can also reach the nume support team seven days a week if you have questions about how a dose went in.

What a stretch mark actually is, and why the fat layer beneath it still works

A stretch mark forms when the dermis is pulled rapidly (during growth, pregnancy, or weight change) causing collagen fibres to break and leave a visible scar. That scarring is confined to the dermis itself. Below it, the subcutaneous fat layer remains present and vascularised in the same way as unscarred skin nearby.

Wegovy's active ingredient, semaglutide, is a GLP-1 receptor agonist absorbed through the subcutaneous tissue into the bloodstream. The NHS medicines page for semaglutide describes the abdomen, outer thigh and upper arm as the standard injection sites, all areas where stretch marks are common. Manufacturers and clinical guidelines endorse these same sites because the fat layer is accessible and consistent there. A stretch mark on the skin's surface doesn't create a meaningful barrier to a correctly placed subcutaneous injection.

If you'd like more detail on what occurs at the point of injection, our page on what happens if you inject Wegovy into a stretch mark goes deeper into the mechanism.

Practical technique when you're working around stretch marks

The key habit is rotation rather than avoidance. Injecting repeatedly into exactly the same patch of skin (with or without a stretch mark) can lead to lipohypertrophy, a fatty lump under the skin that changes how the medicine absorbs. Weekly rotation across the approved sites keeps absorption predictable.

If a stretch mark sits directly over your preferred spot, simply shift a couple of centimetres to one side. Pinch an inch of skin gently, insert the needle at the angle described in the Patient Information Leaflet, and hold until the pen clicks and the dose counter reaches zero. The guide to how Wegovy is injected walks through the full process. For those using the thigh specifically, the page on injecting Wegovy into the thigh covers positioning in more detail.

Changing the needle before each injection, keeping the pen refrigerated between doses, and cleaning the injection site with an alcohol swab beforehand are all straightforward steps that protect the site. A fresh needle also means less resistance going in, which helps with accuracy on uneven skin. If you're ever unsure whether you've placed the needle correctly, our guidance on injecting Wegovy into the arm explains how to position that site safely, and a separate page covers what to do if you think you may have injected Wegovy into muscle rather than the subcutaneous layer.

What to watch for, and when to seek help

Most injection-site reactions are mild: a small red mark, minor bruising or brief tenderness that clears within a day or two. These are listed in Wegovy's prescribing information and are not cause for alarm on their own.

Reach out promptly if you notice: redness or swelling that is spreading rather than fading; skin that feels hard, warm or unusually painful several hours after injecting; a lump that persists for more than a week; or any sign of pus or discharge. These could indicate a localised reaction or infection that a clinician should assess.

Separately, if you experience severe stomach pain (particularly pain that reaches into your back) nausea and vomiting at the same time, that combination warrants urgent medical attention regardless of where you injected. The MHRA highlighted acute pancreatitis as a known, infrequent but serious risk associated with GLP-1 medicines in a Drug Safety Update published in January 2026; the symptoms above are the ones to act on quickly. Any suspected side effect can be reported directly through the MHRA Yellow Card scheme.

If you're thinking about the broader cost and clinical picture of staying on Wegovy, the Wegovy prices page explains what a private prescription typically includes. And if you'd like a clinical review of your injection technique or how your treatment is going, speaking to our prescribers is the right next step.