What's typical
Mild redness, slight swelling, itching, or a small bruise at the injection site are common with weekly GLP-1 injections and generally resolve within a day or two on their own. These reactions tend to become less frequent as you get more experienced with injection technique and rotate sites consistently.
Practical tips to reduce site reactions
- Rotate injection sites systematically (e.g., alternating between abdomen, thigh, and upper arm, and moving within each region) rather than repeatedly using the same exact spot.
- Let the medication reach room temperature before injecting if it's been refrigerated, since injecting cold medication can increase discomfort and reaction likelihood.
- Avoid injecting into scar tissue, moles, or areas with existing irritation.
- Apply gentle pressure, not rubbing, after injection if there's minor bleeding or bruising.
- Use a clean, new needle each time — reusing needles increases both discomfort and infection risk.
When a reaction is worth raising with your prescriber
- Redness or swelling that's spreading, worsening after 48 hours, or accompanied by warmth and increasing pain (possible signs of infection)
- A firm lump that doesn't resolve over time, which can indicate lipohypertrophy (fatty tissue changes from repeated injection in the same spot) — worth mentioning so you can adjust your rotation pattern
- Any signs of a broader allergic reaction — hives, swelling beyond the injection site, difficulty breathing — which warrant prompt medical attention, not just a routine follow-up
The bottom line
Mild, short-lived injection site reactions are a normal and expected part of weekly GLP-1 injections — good rotation technique minimizes them, and anything spreading, worsening, or suggestive of infection or allergic reaction is worth prompt medical attention rather than waiting it out.