Guselkumab (Tremfya)

Guselkumab is a biologic medication used to treat adult patients with moderate-to-severe plaque psoriasis who are candidates for systemic therapy or phototherapy. This medication is a type of antibody that blocks a protein in the body called interleukin-23 (IL-23). IL-23 plays a role in psoriasis and psoriatic arthritis.

How to Take It

Guselkumab is given as an injection under the skin (a subcutaneous injection). The medicine can be injected into the thigh or abdomen. The site of injection should be rotated so the same area is not injected multiple times. Guselkumab comes in pre-filled syringes. The dose is 100 mg. It is given at week 0, week 4, and then every 8 weeks. Some patients will start to improve within a few weeks, but it may take several months to take full effect.

Side Effects

Guselkumab may lower your immune system and the ability to fight infections. Before starting guselkumab all patients should be tested for tuberculosis. Sinus infections, stomach infections, fungal infections, and herpes simplex infections occur more frequently individuals who are taking the medication.

Before starting this medication talk with your rheumatology care team about getting tested for tuberculosis. In general, patients who may become pregnant should use effective contraception while using this medication. Guselkumab has not been studied during pregnancy and breastfeeding. If you forget to take a dose, take it as soon as you remember, then take the next dose at the appropriate scheduled time.

Tell Your Rheumatology Provider

If you develop signs of an infection or have any side effects, especially fever, or allergic reactions, you should stop taking the medication and contact your rheumatology healthcare team. If you are pregnant, planning to get pregnant, or are breastfeeding, let your team know before starting this medication. Guselkumab has not been studied during pregnancy or breastfeeding. If you are planning to have surgery or get any live vaccinations (nasal spray flu vaccine, measles, mumps, rubella, or yellow fever vaccines) talk to your rheumatology healthcare team first.

Updated February 2026 by Shreena Gandhi, MD, and reviewed by the American College of Rheumatology Committee on Communications and Marketing.

This information is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.