Semaglutide injection site reactions: 5 patterns
Local reactions on semaglutide follow the same five patterns as tirzepatide. Slightly different excipient profile may produce different reactions for individual patients.
The mechanism
Subcutaneous injection of semaglutide formulation can produce local reactions to the active drug or to formulation excipients. Wegovy (high-dose semaglutide) and Ozempic (lower-dose) use slightly different concentrations but the same active molecule. Some patients react to one and not the other; the difference is usually formulation-specific rather than drug-specific.
What to expect
About 5-15% of semaglutide patients develop some local reaction. Most are minor and self-resolving. Patterns are reproducible within a patient: same shape, same size each injection.
Management
Same five-pattern framework as tirzepatide. Mild irritation: nothing required. Persistent firm lump: switch regions for 6-8 weeks. Urticarial reaction: antihistamine pre-treatment, topical hydrocortisone after. Delayed-onset: document, discuss with prescriber. Suspected infection: medical attention. Prevention: room-temperature pen, four-quadrant rotation, perpendicular injection, full hold time.
When to escalate
Reactions extending more than 5cm. Systemic symptoms. Reactions worsening 24-48 hours post-injection. Same thresholds as tirzepatide.
- STEP-1 (Wilding et al., NEJM 2021)