Semaglutide skin side effects: what actually happens and when to act

What skin reactions does semaglutide actually cause at the injection site?

The most frequently reported skin side effects are localised to wherever you inject: a patch of redness, a small lump, mild bruising or slight swelling. These reactions are common with any subcutaneous injection and, for most people, clear within a few hours to a day or two. The full side-effect profile of Wegovy extends well beyond the skin, but at the injection site specifically, the issue is usually mechanical rather than a sign that the medicine is causing harm.

Rotating between the abdomen, thigh and upper arm each week is the single most practical step you can take to reduce site reactions. Injecting into the same spot repeatedly causes tissue irritation that builds over time. Letting each area rest for at least a week before reusing it makes a noticeable difference. If you notice a hard lump that does not resolve within a week, or if the site becomes warm, oozing or increasingly painful, contact your prescriber rather than waiting for your next check-in. For a thorough overview of skin changes specifically associated with Wegovy, the Wegovy skin side effects page covers the topic in more detail.

Can semaglutide cause itching or a rash away from the injection site?

Yes, though less commonly. Some people taking semaglutide report generalised itching (pruritus) or a rash on parts of the body that have no contact with the pen. This can reflect a mild immune response and often settles without any change to treatment. The question worth asking is whether the itching is isolated and mild, or whether it is spreading, worsening or accompanied by other symptoms.

If itching develops alongside facial or lip swelling, a widespread raised rash (urticaria), tightening of the throat or any difficulty breathing, those are signs of a potentially serious allergic reaction and you should call 999 or go to an emergency department straight away. Do not wait to see whether it passes. For a focused look at itching specifically, the semaglutide itchy skin page walks through the likely causes and what each pattern suggests. If you want to understand the full range of reactions that can occur, our page on side effects from semaglutide covers what patients commonly experience across the body, not just at the skin. The electronic Medicines Compendium (eMC) also holds the full Wegovy Patient Information Leaflet, which lists hypersensitivity reactions and what action to take.

Is the hair loss people report actually a semaglutide skin side effect?

Hair shedding (sometimes described as clumps in the shower or noticeably more hair on the brush) comes up regularly in conversations our prescribers have with patients a few months into treatment. The condition is called telogen effluvium, and the evidence points to rapid calorie reduction as the trigger rather than semaglutide itself. The follicle cycle pauses temporarily under nutritional stress; regrowth typically begins once weight loss slows or stabilises, usually within six to twelve months.

This does not mean you should simply accept it without discussion. If shedding is significant or distressing, it is worth raising at your next clinical review. Adequate protein intake during treatment is frequently cited as a protective factor. Our dedicated page on a particular side effect of semaglutide can help you understand whether what you are noticing fits a recognised pattern or warrants closer attention. A look at the broader semaglutide side effects picture puts hair changes in the context of the other things that commonly shift in the first few months, which can help in separating what is expected from what deserves attention.

When should you get medical help, and how do you report skin side effects?

Seek emergency help (call 999 or go to A&E) for any combination of facial or throat swelling, widespread hives, difficulty breathing or a sudden drop in blood pressure after an injection. These can indicate anaphylaxis and cannot wait.

Contact your prescriber the same day (or urgently out of hours) for: a rash that is spreading or blistering; significant swelling at or around the injection site; itching that is waking you at night or affecting your day; or any skin change you cannot explain. For questions that are not urgent, the contact page gives you the aftercare routes, and the FAQs section covers questions our prescribers field regularly.

You can also report any suspected side effect directly to the MHRA using the Yellow Card scheme. Reports from patients as well as clinicians help the regulator build a clearer picture of how medicines behave in everyday use. Wegovy carries a black triangle (▼), which means the MHRA actively invites additional reporting as part of ongoing safety monitoring.

If you would like to discuss skin side effects or any other concern before starting or continuing treatment, speaking to our prescribers is the starting point. Suitability, side-effect management and what to watch for are covered as part of every consultation. You can also read more about our clinical team on the clinical team page.