# Injection site reactions on GLP-1s and peptides: what to track, where, and how to log them

> Injection site reactions range from 0.2% (Ozempic) to 6-8% (Zepbound) and 13.9% (Saxenda) on the labels. What to log per site and how to track it with Peppy's body map.

Source: https://peppytracker.com/side-effects/injection-site-reaction/
Last updated: 2026-08-30

Injection site reactions (redness, itching, pain, swelling, bruising) are listed on every GLP-1 label: Ozempic 0.2%, Wegovy 1.4%, Mounjaro 3.2%, Zepbound 6-8%, Saxenda 13.9%. Egrifta's tesamorelin label lists 17% versus 6% on placebo. The thing to log is which site, which shot, and a 1-5 severity, so a body-map log can show whether one site keeps reacting.

## Injection site reaction: what it is and who reports it

An injection site reaction is anything local that happens where the needle went in: redness, itching, a small lump, tenderness, a rash, a bruise. It is the one side effect where the important question is not "how bad" but "where", because the fix, if there is one, is usually about the site and the technique rather than the compound.

Every GLP-1 label lists it, with a wide spread:

| Label | Injection site reactions (drug) | Placebo |
| --- | --- | --- |
| Ozempic | 0.2% | not stated |
| Wegovy 2.4 mg | 1.4% | 1% |
| Mounjaro | 3.2% | 0.4% |
| Zepbound 5 / 10 / 15 mg | 6% / 8% / 8% | 2% |
| Saxenda (daily) | 13.9% | 10.5% |
| Egrifta SV (tesamorelin, daily) | 17% | 6% |

Two things jump out. The daily shots (Saxenda, Egrifta) list far more reactions than the weekly ones, which fits: more needles, more chances. And Zepbound's label notes that reactions were much more frequent in people who developed anti-tirzepatide antibodies (11.3%) than in those who did not (1%). Zepbound's label lists the types as "injection site bruising, injection site erythema, injection site pruritus, injection site pain, injection site rash"; Egrifta's adds urticaria, swelling, irritation and hemorrhage.

For research compounds like [BPC-157](https://peppytracker.com/compounds/bpc-157/), [TB-500](https://peppytracker.com/compounds/tb-500/) and [CJC-1295 / Ipamorelin](https://peppytracker.com/compounds/cjc-1295-ipamorelin/) there is no label and no figure. Peppy flags injection site reaction as common for injectables in general. Many people report that reconstituted peptides sting more than pens, and that it varies by site. Neither is on a label.

## When it tends to show up

Unlike gut side effects, site reactions are not tied to escalation weeks in the labels. They are tied to the shot. Many people report redness or itching within hours and a small lump or tenderness that lasts one to three days. A reaction that appears days later, or grows rather than fades, is a different thing and belongs in the prescriber section below.

The pattern worth finding is **site-specific**: does one spot keep reacting while others do not? Many daily-peptide users report that the abdomen reacts less than the thigh, or the opposite, and that reactions drop off once they stop reusing the same square inch. That is only visible if you log the site every time. The [injection site rotation guide](https://peppytracker.com/guides/injection-site-rotation/) covers the 13 sites Peppy uses and how it suggests the next one.

## What is worth logging

- **The site, every shot.** Not "stomach" but which quadrant. This is the whole log.
- **Severity, 1-5, the next day.** Reactions peak after the shot, so score them in the following day's check-in.
- **What it looked like, in the note.** "Red, coin-sized, itchy", "small hard lump", "bruise". Words the label uses are the words a prescriber will ask for.
- **Which protocol.** If you run more than one compound, the reaction may follow one of them. Peppy colour-codes each protocol on the calendar.
- **Bruising separately.** A bruise is a needle-and-vessel event, not an immune one; Peppy tracks [bruising](https://peppytracker.com/side-effects/bruising/) as its own score.
- **A photo (Pro).** Progress photos in Peppy stay on your device and iCloud. A dated photo of a reaction is the quickest way to show a prescriber what happened.

## When to contact your prescriber

- **Hypersensitivity, not site reaction.** The labels track these separately: Mounjaro 3.2% versus 1.7%, Zepbound 5% versus 3%. Hives beyond the site, swelling of the face, lips or throat, or difficulty breathing is an emergency.
- **A site that is hot, hard, spreading or more painful each day.** That is not a normal reaction and needs a same-day call.
- **Reactions at every shot, or getting worse over weeks.** Zepbound's antibody note is one reason a prescriber may want to know. Bring the site log.

Rotation and technique questions belong with whoever taught you to inject. Peppy can show which sites reacted; it does not tell you what to change.

## How to do this in Peppy

1. **Turn injection site reaction on.** Open Settings ▸ Tracking and toggle Injection site reaction. Add Bruising if you want it separate.
2. **Log every shot on the body map.** Tap the dose on the Today tab. The Log shot sheet shows a front/back silhouette with 13 sites; Peppy marks the one it suggests and shows "Last used 6 days ago" on the others. Tap the site you actually used, adjust the time if needed, add a note, save.
3. **Score the reaction the next day.** In the daily check-in, set injection site reaction 1-5 and describe it in the note. If it is a bruise, score bruising instead.
4. **Look at the site heat-map (Pro).** In the protocol's rotation settings, Peppy shows a heat-map of how often each site has been used and lets you set a custom rotation order. Compare it against your reaction scores: a site that is overused and always reacting is the finding.
5. **Read Progress (Pro) for the timeline.** The injection site reaction row on the weekly heat-map shows whether reactions cluster after a dose change or a new vial. Free users see it blurred.
6. **Use the Calendar to match a reaction to a shot.** Tap the day, see the shot and its site, and you know exactly which injection caused it.

Related: [bruising](https://peppytracker.com/side-effects/bruising/), [flushing](https://peppytracker.com/side-effects/flushing/), the [BPC-157 tracker](https://peppytracker.com/trackers/bpc-157-tracker/) and the [side-effects tracking guide](https://peppytracker.com/guides/track-glp-1-side-effects-food-noise/).

## Frequently asked

### What does an injection site reaction look like?

Zepbound's label lists injection site bruising, erythema (redness), pruritus (itching), pain and rash. Egrifta's tesamorelin label adds urticaria (hives), swelling, irritation and hemorrhage. Most are small, local and settle within days. Log the site, the day and a 1-5 score.

### How common are injection site reactions on Mounjaro or Zepbound?

Mounjaro's label lists them in 3.2% of patients versus 0.4% on placebo. Zepbound's lists 6%, 8% and 8% at 5, 10 and 15 mg versus 2%. Zepbound's label also notes they were far more frequent in patients who developed anti-tirzepatide antibodies (11.3%) than those who did not (1%).

### Are injection site reactions worse with peptides than GLP-1s?

There is no label for research compounds like BPC-157 or TB-500, so no figure exists. The one prescribed peptide with a label, Egrifta SV (tesamorelin), lists injection site reactions in 17% versus 6% on placebo, and 25% versus 14% in its warnings section. Many people report reactions are more about technique and rotation than the compound.

### Should I rotate injection sites to avoid reactions?

Rotation is standard advice in the labels' instructions for use, and many people report fewer reactions when they do not reuse the same spot. Peppy suggests the next site on a 13-site body map and shows when each was last used. See the injection site rotation guide.

### When should I call the doctor about an injection site reaction?

The labels list hypersensitivity reactions separately from site reactions: Mounjaro 3.2% versus 1.7%, Zepbound 5% versus 3%. Spreading redness, hives beyond the site, swelling of the face or throat, or trouble breathing is an emergency. A hot, hard, increasingly painful site over days is a same-day call.

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Peppy is a tracking tool, not medical advice. Dose calculations are mathematical conversions only. Always follow your prescriber's instructions and verify every draw-up yourself.

Peppy is a free iPhone app (Pro subscription optional). App Store: https://apps.apple.com/us/app/peptide-tracker-peppy/id6775005514