What the label lists and what reports show
Guselkumab side effects
Guselkumab's FDA label: “Most common adverse reactions associated with TREMFYA are: Plaque Psoriasis and Psoriatic Arthritis (≥1%): upper respiratory infections, headache, injection site reactions, arthralgia, bronchitis, diarrhea, gastroenteritis, tinea infections, and herpes …” FAERS holds 35,559 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is accidental exposure to product (3,518 reports).
- No generic listed
Check it at the source: the guselkumab FDA label on DailyMed (effective June 4, 2026, Janssen Biotech, Inc.); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of TREMFYA?TREMFYA may cause serious side effects including: See " What is the most important information I should know about TREMFYA? " The most common side effects of TREMFYA include: respiratory tract infections joint pain (arthralgia) fungal skin infections bronchitis skin rash (rash) headache diarrhea herpes simplex infections feeling very tired (fatigue) injection site reactions stomach flu (gastroenteritis) stomach pain fever (pyrexia) These are not all the possible side effects of TREMFYA. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Source: FDA drug label, Janssen Biotech, Inc., effective June 4, 2026 (SPL set 1e6dc9ae-1c4c-42d9-87aa-c315ecc51b56), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions associated with TREMFYA are: Plaque Psoriasis and Psoriatic Arthritis (≥1%): upper respiratory infections, headache, injection site reactions, arthralgia, bronchitis, diarrhea, gastroenteritis, tinea infections, and herpes simplex infections.
Table 1: Adverse Reactions Occurring in ≥1% of Adult Subjects with Moderate-to-Severe Plaque Psoriasis through Week 16 in Trials PsO1 and PsO2
| Reaction | TREMFYA Subjects receiving 100 mg of TREMFYA at Week 0, Week 4, and every 8 weeks… | Adalimumab U.S. licensed adalimumab N=196 n (%) | Placebo N=422 n (%) |
|---|---|---|---|
| Upper respiratory infections Upper respiratory infections include nasopharyngitis, upper… | 118 (14.3) | 21 (10.7) | 54 (12.8) |
| Headache Headache includes headache and tension headache. | 38 (4.6) | 2 (1.0) | 14 (3.3) |
| Injection site reactions Injection site reactions include injection site erythema,… | 37 (4.5) | 15 (7.7) | 12 (2.8) |
| Arthralgia | 22 (2.7) | 4 (2.0) | 9 (2.1) |
| Diarrhea | 13 (1.6) | 3 (1.5) | 4 (0.9) |
| Gastroenteritis Gastroenteritis includes gastroenteritis and viral gastroenteritis. | 11 (1.3) | 4 (2.0) | 4 (0.9) |
| Tinea infections Tinea infections include tinea pedis, tinea cruris, tinea infection, and… | 9 (1.1) | 0 | 0 |
| Herpes simplex infections Herpes simplex infections include oral herpes, herpes simplex,… | 9 (1.1) | 0 | 2 (0.5) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following adverse reactions are discussed in greater detail in other sections of labeling: Hypersensitivity Reactions [see Contraindications (4) and Warnings and Precautions (5.1) ] Infections [see Warnings and Precautions (5.2) ] Tuberculosis [see Warnings and Precautions (5.3) ] Hepatotoxicity [see Warnings and Precautions (5.4) ] Most common adverse reactions associated with TREMFYA are: Plaque Psoriasis and Psoriatic Arthritis (≥1%): upper respiratory infections, headache, injection site reactions, arthralgia, bronchitis, diarrhea, gastroenteritis, tinea infections, and herpes simplex infections. ( 6.1 ) Ulcerative Colitis (≥3%): injection site reactions, arthralgia, upper respiratory tract infections, headache, gastroenteritis, fatigue, pyrexia, and rash. ( 6.1 ) Crohn's Disease (≥3%): respiratory tract infections, abdominal pain, injection site reactions, headache, fatigue, arthralgia, diarrhea, and gastroenteritis. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Janssen Biotech, Inc. at 1-800-526-7736 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. …
Source: FDA drug label, Janssen Biotech, Inc., effective June 4, 2026 (SPL set 1e6dc9ae-1c4c-42d9-87aa-c315ecc51b56), via openFDA; the full label on DailyMed
What do FAERS reports show?
35,559 reports list guselkumab among the medicines taken, each a report of something that happened, not proof the medicine caused it; 458 are coded as a death and 2,667 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Reports rose sharply in 2025 (6,819, against a median of 2,193 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 17 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Guselkumab: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions