Wegovy® injection site reactions

The site figure and its neighbours

Section 6.1 of the US label reports injection site reactions in text rather than in a table, because at 1.4% they fall below the adult table’s 2% cut-off. ^[1] The table below sets that figure next to the EU and Canadian versions and other skin findings, so the differences are clear.

What counts as a site reaction

The US label groups itching (pruritus), redness (erythema), inflammation, hardening of the skin (induration) and irritation at the injection site. ^[1] The Canadian monograph casts a wider net, adding swelling, hives, tingling at the site and a general “injection site reaction” term, yet arrives at the same 1.4% against 1.0%. ^[3] The placebo injections caused such reactions in about 1 person in 100, a reminder that the needle and the act of injecting play a part on their own.

None of the three documents says how long site reactions lasted, whether they rose at higher doses, or gives a separate teenage figure.

Skin changes the label keeps separate

• Dysesthesia: altered skin sensations such as tingling, burning, sensitive skin and skin pain, not limited to the injection site. It became more frequent with higher doses and drug levels: 22% on 7.2 mg against 6% on 2.4 mg in the high-dose trials. The Medication Guide calls it “changes in skin sensations”. ^[1]
• Rash and hives: each in 3% of teenagers on Wegovy® and none on placebo. ^[1]
• Allergy linked to antibodies: in adult trials, allergic reactions occurred in 16% of people who developed anti-semaglutide antibodies and 7% of those who did not. ^[1] The EU document says antibodies were found in 2.9–10.9% of people on 2.4 mg and 15.3% on 7.2 mg, were transient and had no apparent effect on efficacy or safety. ^[2]
• Serious allergic reactions: anaphylaxis and angioedema (swelling under the skin) have been reported; section 5.7 says to stop the medicine if they occur. ^[1]

What research adds

A 2026 meta-analysis pooled 14 randomised trials of GLP-1 medicines that reported site reactions (4,861 patients, 396 events) and found them about 3.5 times as likely as with comparators (risk ratio 3.55). ^[4] Broader skin events were infrequent and not significantly raised. In the US FDA voluntary reporting database, the clearest site-reaction signals, such as bleeding at the site, were for exenatide and dulaglutide rather than semaglutide. ^[4] Disproportionality signals of this kind show reporting patterns, not rates or proof of cause.

Sites and technique in the instructions

Section 2.1 says Wegovy® goes into the fatty layer beneath the skin of the belly, a thigh or an upper arm, that the site should be rotated with each dose, and that the time of day and site can change without changing the dose. ^[1] Section 12.3 reports similar exposure whichever area is used, and the Medication Guide adds not to inject into a muscle or a vein. ^[1]

The Instructions for Use for the single-dose pen add practical detail: keep at least 2 inches from the belly button; avoid skin that is tender, bruised, red or hard, and areas with scars or stretch marks; clean the skin with an alcohol swab or soap and water and let it dry; then press the pen firmly and keep pressing until the yellow bar stops moving, which takes about 5 to 10 seconds. If medicine appears on the skin, the instructions say to keep pressure on until the bar stops next time; if blood appears, press the site lightly with gauze or cotton. ^[1] The FlexTouch® pen instructions ask you to keep pressing the button with the needle in the skin and count slowly to 6. ^[1]

In the EU, the 7.2 mg dose can be given as one injection or as three 2.4 mg injections in the same body area, at least 5 cm apart. ^[2] The US label asks that patients be trained on the exact presentation they receive and retrained if it changes. ^[1]

Other causes, and what general guidance says

Not every red patch is a drug reaction. MedlinePlus describes cellulitis, a skin infection, as redness that gets bigger, warmth, tenderness, a tight or glossy look and sometimes fever, chills and fatigue, and notes that a provider may mark the edge of the redness with a pen to see whether it spreads. ^[5] Hives, raised itchy bumps, are usually caused by an allergic reaction to a medicine or food; they often go away on their own, but swelling of the airway is an emergency. ^[6]

Section 5.11 is absolute: a Wegovy® FlexTouch® pen must never be shared, even with a new needle, because of the risk of passing on blood-borne infections. ^[1] The label does not suggest creams or antihistamines for site reactions; ask your pharmacist or prescriber before using one.

Wegovy® and FlexTouch® are registered trademarks of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.