# GLP-1 Injection Site Reactions: When to Contact Your Care Team

What the prescribing information says about injection site reactions on Wegovy and Zepbound, which signs point to an allergic reaction, and what to log before you call.

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Prepared by [Ēlovi Editorial](https://joinelovi.com/blog/authors/elovi-editorial).
Published: 2026-10-17T14:38:00.000Z. Updated: 2026-10-17T14:38:00.000Z.
Prepared by Ēlovi Editorial with AI assistance. Sources checked: 2026-10-17. Reviewed by the Ēlovi editorial team, which includes licensed clinicians.
[Editorial process](https://joinelovi.com/blog/editorial-policy).

## The short answer

Injection site reactions such as itching, redness, or irritation are listed as reported side effects of semaglutide \(Wegovy\) and tirzepatide \(Zepbound\), and they were uncommon in the weight-reduction trials. Tell your care team about any reaction that is severe or does not go away. Swelling of the face, lips, tongue, or throat, trouble breathing or swallowing, a severe rash or itching, fainting, or a very rapid heartbeat can be signs of a serious allergic reaction and need emergency care.

## Which signs need emergency care, not a wait-and-see approach?

Get emergency medical help if, after an injection, you have swelling of your face, lips, tongue, or throat, problems breathing or swallowing, a severe rash or itching, fainting or feeling dizzy, or a very rapid heartbeat. The Wegovy Medication Guide lists these as symptoms of a serious allergic reaction. [1](https://www.novo-pi.com/wegovy.pdf)

Serious hypersensitivity reactions, including anaphylaxis and angioedema, have been reported with both semaglutide and tirzepatide. The Zepbound label says patients who have a hypersensitivity reaction should promptly seek medical attention. [1](https://www.novo-pi.com/wegovy.pdf) [2](https://pi.lilly.com/us/zepbound-uspi.pdf)

MedlinePlus lists swelling around the face, throat, mouth, or eyes, hives, rash, itching, and trouble breathing or swallowing in its warnings for both medicines. [3](https://medlineplus.gov/druginfo/meds/a618008.html) [4](https://medlineplus.gov/druginfo/meds/a622044.html)

None of this is a full list, and you do not need to match your symptoms to it first. If you feel seriously unwell, get care. Ask a clinician what to do before your next injection.

## What counts as an injection site reaction?

An injection site reaction is a change in the skin where the medicine went in. The Wegovy label names itching, redness, inflammation, hardening, and irritation. [1](https://www.novo-pi.com/wegovy.pdf) The Zepbound label groups reactions such as bruising, redness, itching, pain, and rash at the site under one heading. [2](https://pi.lilly.com/us/zepbound-uspi.pdf)

A reaction at the site is not the same as an allergic reaction that affects your whole body. The signs in the first section above are the ones that cross that line. Anything on your skin that is spreading, getting worse, or accompanied by feeling generally unwell is worth telling your care team about promptly, rather than guessing which category it falls in.

## How common are injection site reactions in the trials?

Uncommon, but not rare. In the Wegovy weight-reduction trials, 1.4% of treated adults and 1% of adults on placebo had injection site reactions. [1](https://www.novo-pi.com/wegovy.pdf) In the Zepbound weight-reduction trials, reactions were reported by 2% of people on placebo and by 6% to 8% of people on tirzepatide, depending on the dose group. [2](https://pi.lilly.com/us/zepbound-uspi.pdf)

Those figures come from different trials with different designs, so they cannot be compared head to head. They also describe groups of people, not what will happen to you.

The Zepbound label adds one finding: in the pooled trials, injection site reactions were more frequent in people who developed anti-tirzepatide antibodies (11.3%) than in those who did not (1%). [2](https://pi.lilly.com/us/zepbound-uspi.pdf) The label does not tell you what to do about that, and you cannot tell from your skin whether you have antibodies. It is a reason to report repeated reactions rather than assume they will stop.

## Does rotating the injection site matter?

Both labels instruct you to rotate injection sites with each injection. The Wegovy Medication Guide says not to use the same site every time. [1](https://www.novo-pi.com/wegovy.pdf) [2](https://pi.lilly.com/us/zepbound-uspi.pdf) Both medicines are injected under the skin of the abdomen, thigh, or upper arm. [1](https://www.novo-pi.com/wegovy.pdf) [4](https://medlineplus.gov/druginfo/meds/a622044.html)

The labels do not say rotation prevents reactions, so this article does not claim it will. It is the instruction on the label, and it is a sensible thing to confirm when you review your technique with your care team. If you feel unsure about injecting at all, our article on [feeling nervous about GLP-1 injections](https://joinelovi.com/blog/nervous-about-glp-1-injections-questions-and-support-options) covers that conversation.

For how to prepare and use your own pen, follow the Instructions for Use that came with your product and ask your prescriber or pharmacist. This article does not give injection or dosing instructions.

## What should you log before you call?

A short record turns "my arm looked odd" into something a clinician can work with. Here is a log you can copy into your notes app.

| What to record | Example entry | Why it helps |
| --- | --- | --- |
| Date, time, and body area injected | "Thursday evening, left thigh" | Shows whether reactions follow one area |
| When you first noticed the change | "About two hours later" | Timing separates a local reaction from an immediate one |
| What it looks and feels like | "Red patch, itchy, no swelling elsewhere" | Gives the clinician a description to work from |
| How long it lasted, and whether it is changing | "Faded by Saturday" or "larger today" | Persistent or spreading changes need review |
| Anything else you noticed | "Hives on my arms" or "none" | Signs beyond the site may point to an allergy |
| Your product and any new product or soap used | "Pen I was prescribed; new body lotion" | Helps rule other causes in or out |

Take a photo if you can, with the date. You may be asked to send one.

## What does a clinician assess, and what should you ask?

A clinician can look at the skin, ask about timing, and ask whether this has happened before. They can also review how you are injecting and decide whether anything about your treatment should change. That decision is theirs, and it depends on your history.

Questions worth asking:

- Is what I am describing a local reaction, or could it be an allergic one?
- Should I keep taking my next injection while this settles, or wait to hear from you?
- Can you watch me or talk me through my injection technique and site choice?
- What would make you want to see me in person or send me to urgent care?
- Is there anything in my other medicines or skin products that could be involved?

If you are early in treatment, our guide to [starting a GLP-1](https://joinelovi.com/blog/starting-glp-1) explains what follow-up usually looks like, and the [GLP-1 side effects overview](https://joinelovi.com/blog/glp-1-side-effects) places this one among the others. For an emergency, call your local emergency number rather than messaging anyone.

## Common questions

### Is a small bruise or drop of blood normal?

Bruising at the site is one of the reactions the Zepbound label groups under injection site reactions. [2](https://pi.lilly.com/us/zepbound-uspi.pdf) The Wegovy Instructions for Use say that if blood appears after an injection, you should press the site lightly. [1](https://www.novo-pi.com/wegovy.pdf) Neither tells you that a particular bruise is harmless, so mention frequent or large bruising at your next visit.

### What if the reaction only happens sometimes?

Tell your care team anyway and bring the log above. The labels do not say how to manage repeated reactions, so that call belongs to a clinician who knows your history.

## References

1. [WEGOVY \(semaglutide\) injection: Prescribing Information and Medication Guide](https://www.novo-pi.com/wegovy.pdf) — Novo Nordisk
2. [ZEPBOUND \(tirzepatide\) injection: Prescribing Information](https://pi.lilly.com/us/zepbound-uspi.pdf) — Eli Lilly and Company
3. [Semaglutide Injection](https://medlineplus.gov/druginfo/meds/a618008.html) — MedlinePlus, U.S. National Library of Medicine
4. [Tirzepatide Injection](https://medlineplus.gov/druginfo/meds/a622044.html) — MedlinePlus, U.S. National Library of Medicine

For general education; this does not replace medical advice or an individual evaluation. Talk to your clinician before starting, changing, or stopping treatment. Compounded medications are not FDA-approved.