Bruising with Wegovy: causes, what's normal and when to act

Why does Wegovy cause bruising at the injection site?

The short answer is physics. Wegovy is a subcutaneous injection, meaning the needle goes into the fatty layer just below the skin. That layer is threaded with tiny capillaries, and occasionally the needle clips one. When it does, a small amount of blood leaks into the surrounding tissue and you see a bruise. It has very little to do with technique and a lot to do with anatomy, capillaries are too small to see or avoid.

The bruise is nearly always localised: a small patch, tender for a day or so, that moves through the usual yellow-green colour sequence and disappears within a week. Semaglutide's mechanism does not thin the blood or affect platelets, so the bruise itself is not a sign the medicine is doing something it should not. The NHS semaglutide patient guide lists injection-site reactions (including bruising, redness and swelling) among the more common side effects, most of which settle on their own.

One practical habit worth trying: after you inject, hold the pen in place for a count of ten before withdrawing it, then apply gentle pressure with a clean finger for another thirty seconds. It takes under a minute and can meaningfully reduce the pooling of blood that causes a bruise.

Does the bruising get worse with each dose or improve over time?

For most people, bruising with Wegovy tends to become less frequent as the weeks go on. Your injection technique naturally improves, you get a feel for which sites suit your anatomy, and the tissue adjusts to regular injections. There is no evidence that semaglutide itself causes progressive or cumulative bruising, what you experience in week two is not necessarily a preview of week twelve.

A few things can make bruising more likely at any point. Injecting into an area you have used recently is one of the most common causes of repeated bruising; the tissue has not fully healed and is more fragile. Injecting over a muscle or into skin that is unusually thin can also increase the chance of clipping a vessel. If you are taking medicines that affect clotting (aspirin, warfarin, certain anti-inflammatory drugs) your prescriber should already know, but it is worth flagging again if bruising feels heavier than expected. You can find a fuller discussion of what drives bruising patterns on Wegovy if you want to explore this further.

Some people find that injecting cold from the fridge (rather than letting the pen reach room temperature first) increases discomfort and bruising slightly. The SmPC recommends warming the pen to room temperature before use, worth checking if you are skipping that step.

Is there a point where bruising after a Wegovy injection needs medical attention?

Most injection-site bruises do not need anything beyond patience. The cases worth acting on tend to look different from a routine bruise in one or more of these ways.

A bruise that is significantly larger than your palm, that keeps spreading over several days rather than fading, or that is accompanied by swelling, heat, or a feeling of hardness in the tissue could suggest something beyond a clipped capillary. If you are wondering whether Wegovy can cause bruising beyond the injection site, that page covers the distinction in more detail. And if you notice that bruising has become very easy across your body generally (not just at injection sites) while on Wegovy, that is a conversation to have with a clinician; easy bruising across the body can sometimes reflect changes in nutrition, hydration or other factors that a prescriber can help unpick.

The MHRA's Yellow Card scheme is there for anyone who wants to formally report a suspected side effect, including unusual bruising patterns. Reports help build the safety picture for all patients.

Can anything be done to reduce bruising on Wegovy without stopping treatment?

Yes, and most of the effective steps are simple. Rotating injection sites consistently is the most important. Many people find a structured rotation (working around the abdomen in a clockwise pattern, or alternating between the left and right thigh week by week) keeps each area rested for long enough to recover. Avoid injecting within a few centimetres of last week's site.

Pinching the skin gently before and during injection helps ensure the needle stays in fat rather than muscle. Using a fresh needle every time matters more than people realise; a slightly blunt needle creates more tissue trauma. Alcohol swabs are helpful for cleaning the site, but waiting for the skin to dry before injecting can reduce stinging and minor tissue irritation. If you find you are bruising easily on semaglutide more broadly, that page looks at the range of factors that can contribute and what you can do about them.

There is some interest in whether tranexamic acid (a medicine that helps stabilise blood clots) might reduce injection-site bruising in this context. What the evidence actually says about tranexamic acid and Wegovy is worth reading before drawing conclusions; it is not a standard recommendation, and any new medicine needs to be discussed with a prescriber first.

If you are finding injection-site bruising particularly troublesome and it is affecting your confidence with the injections, our prescribers are used to this question. A quick consultation with our clinical team can review your technique notes and any other medicines you take, and work through options with you. There is no charge for that conversation.