Every approved peptide injection label has a line about the skin where the needle goes in. Read side by side, those lines look like a ranking: some products cause reactions in one patient in two hundred, others in one in four. They are not a ranking. The spread is mostly about how the reactions were counted, what the placebo did, and whether the patient made antibodies — and those three things are exactly what nobody has measured for research-market peptides.
Which body sites each label permits, and why absorption does not decide them, is on our peptide injection sites page. This page is about the reactions.
The census: ten labels, read 5 October 2026
| Product (peptide) | Injection site reactions | Placebo | Note |
|---|---|---|---|
| Trulicity (dulaglutide) | 0.5% | 0.0% | Placebo-controlled adult studies |
| Wegovy (semaglutide) | 1.4% | 1.0% | Adult weight-reduction trials |
| Mounjaro (tirzepatide) | 3.2% | 0.4% | Pooled placebo-controlled trials |
| Zepbound (tirzepatide) | 6–8% | 2% | 6% at 5 mg, 8% at 10 and 15 mg |
| Vyleesi (bremelanotide) | 13.2% | 8.4% | Autoinjector, as-needed use |
| Saxenda (liraglutide) | 13.9% | 10.5% | Daily injection |
| Tymlos, men's trial (abaloparatide) | 13% erythema, 7% swelling, 6% pain | 5%, 0%, 0% | Reported adverse reactions |
| EGRIFTA SV (tesamorelin) | 25% | 14% | First 26 weeks, daily |
| Tymlos, women's trial (abaloparatide) | 58% redness | 28% | Checked daily, one hour after injection |
| Imcivree (setmelanotide) | among the most common (≥20% in at least one indication) | — | Label summary; daily |
Forteo (teriparatide) and Increlex (mecasermin) list injection site reactions — pain, swelling, bruising; for Increlex also bleeding, hardening and lipohypertrophy — without a rate in the sections read here.
Lesson one: the rate depends on who was looking
The Tymlos label carries the clearest demonstration in the set. In its osteoporosis trial in women, injection sites were assessed every day for the first month, one hour after each injection. Redness was recorded in 58% on abaloparatide and 28% on placebo; swelling in 11% against 3%; pain in 10% against 7%. Severe redness was recorded in 2.9%.
In the same label's men's trial, injection site erythema appears in the ordinary adverse-reaction table at 13% against 5%.
Same molecule, same pen. The difference is that in one trial an investigator looked at every injection site every day, and in the other a reaction was recorded when someone reported it. Most label figures are the second kind. A product with a 1% rate on its label has not been shown to cause visible reactions in 1% of injections; it has been shown to produce 1% of patients with a reaction worth reporting.
Lesson two: the placebo injects too
Four labels in the table report placebo rates above 8%. EGRIFTA SV's placebo arm had injection site reactions in 14% of patients over 26 weeks, Saxenda's 10.5%, Vyleesi's 8.4%, and Tymlos's placebo arm had redness in 28% when it was looked for.
A placebo injection contains the vehicle — water, buffer, salt, sometimes a preservative — delivered through the same needle. Much of what happens at the skin happens because something was injected, not because of what the active ingredient is. The peptide's own contribution is the gap between the two columns: 11 points for EGRIFTA SV, about 5 for Vyleesi, under 1 for Wegovy.
The daily products sit at the top of the table and the weekly ones near the bottom. EGRIFTA SV, Saxenda and Tymlos are injected every day; Trulicity, Wegovy, Mounjaro and Zepbound once a week. The labels do not test frequency as a cause, so this is a pattern in the table, not a finding.
Lesson three: antibodies and site reactions travel together
The tirzepatide labels quantify something the others only imply. On the Zepbound label, injection site reactions occurred in 11.3% of patients who developed anti-tirzepatide antibodies and 1% of those who did not. The Mounjaro label reports 4.6% (119 of 2,570) against 0.7% (18 of 2,455) across seven trials, and 6% against 0% in its paediatric trial.
That association is the bridge between a local reaction and a systemic one. An immune response against the peptide shows up first where the peptide is concentrated — in the skin around the injection. It is also why FDA's reviews of compounded research peptides keep naming immunogenicity: on its list of bulk substances that may present significant safety risks, the agency cites potential immunogenicity for thymosin alpha 1, the TB-500 fragment and others, together with peptide-related impurities and aggregation, which raise it.
When a site reaction is the start of an allergic one
The Increlex label states that allergic reactions reported after marketing "range from localized (injection site) reactions to systemic reactions, including anaphylaxis requiring hospitalization." Wegovy reports serious hypersensitivity reactions, including anaphylaxis and angioedema, and the Zepbound and EGRIFTA SV labels carry hypersensitivity warnings of their own.
Hives or itching that spreads beyond the injection site, swelling of the lips, face or throat, wheezing or faintness after an injection are signs of a systemic reaction. Those are emergencies, not site reactions.
What the labels do not cover — the research-market gap
- No rate exists for any research-market peptide. None has a label, a placebo-controlled trial of its own formulation, or a counted injection site figure. Per-compound records are on our peptide side-effects overview, and for the compounds with any human data — such as tesamorelin and ipamorelin — on their own pages.
- No antibody data. The single strongest predictor of site reactions on the tirzepatide labels has never been measured for BPC-157, TB-500 or most other research compounds.
- No specification for the solution. Approved products control pH, tonicity, preservative and particulate matter. A reconstituted research vial's solution depends on the powder and on what it was mixed with; what bacteriostatic water contains and why its benzyl alcohol matters is on our bacteriostatic water page.
- No identity guarantee. An impurity or a different peptide in the vial cannot be ruled out without testing; what a certificate does and does not show is on our how to read a COA page.
How subcutaneous injection itself is described on approved labels is covered on our subcutaneous injection page. A reaction that is spreading, hot, increasingly painful or accompanied by fever can be an infection rather than irritation; that is a question for a clinician.
Sources and dates
All labels read from FDA's structured product labeling via the openFDA label endpoint on 2026-10-05; manufacturer versions used, effective dates in brackets.
- TRULICITY, Eli Lilly (2026-06-16) — section 6, injection-site reactions.
- WEGOVY, Novo Nordisk (2026-06-18; set ID ee06186f) — section 6, injection site reactions; hypersensitivity.
- MOUNJARO, Eli Lilly (2026-08-27) — section 6, injection site reactions and anti-tirzepatide antibodies.
- ZEPBOUND, Eli Lilly (2026-08-28) — section 6 table and injection site reactions by antibody status.
- VYLEESI, Cosette Pharmaceuticals (2025-11-13) — section 6, Table 1.
- SAXENDA, Novo Nordisk (2026-02-25) — section 6 adult adverse-reaction table.
- TYMLOS, Radius Health (2026-08-11) — section 6, women's trial daily injection-site assessment and men's trial table.
- EGRIFTA SV, Theratechnologies (2026-07-29) — section 5.6.
- IMCIVREE, Rhythm Pharmaceuticals (2026-04-01) — highlights, most common adverse reactions.
- FORTEO, Eli Lilly (2026-08-03) and INCRELEX, Eton Pharmaceuticals (2026-05-18) — adverse reactions and, for Increlex, section 5 hypersensitivity.
- FDA. Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks, content current as of 2026-04-22, read 2026-10-05.
Corrections go to the contact page.