Stelara Side Effects: What to Expect and When to Call Your Doctor

Stelara (ustekinumab) is generally considered a well-tolerated biologic, but like any medication that affects the immune system, it can cause side effects — ranging from mild, common reactions to rare but serious complications. Knowing what to expect and what to watch for can help you feel more confident about your treatment and act quickly if something needs medical attention.

Common Side Effects of Stelara (Reported in 3% or More of Patients)

These are the most frequently reported side effects across Stelara's approved indications:

Nasopharyngitis (common cold symptoms): Runny nose, congestion, sore throat. This is the most frequently reported side effect.

Upper respiratory infections: Cough, congestion, mild fever. Usually mild and self-resolving.

Headache: Mild-to-moderate headaches are common, especially early in treatment.

Fatigue: Tiredness is reported by some patients, particularly those with psoriasis.

Injection site reactions: Redness, pain, bruising, or swelling at the injection site. These are typically mild and temporary.

Nausea: More commonly reported in patients using Stelara for Crohn's disease.

Sinusitis, bronchitis: Sinus infections reported in Crohn's disease patients.

Diarrhea, abdominal pain: Reported in patients with ulcerative colitis.

Serious Side Effects: What to Watch For

These side effects are less common but require prompt medical attention:

Serious infections: Stelara weakens the immune system. Serious bacterial, fungal, and viral infections have been reported, including diverticulitis, cellulitis, pneumonia, and sepsis. Seek care immediately for fever, chills, unusual fatigue, or signs of infection.

Tuberculosis (TB) reactivation: Stelara can reactivate latent TB infections. TB testing is required before starting Stelara. Tell your doctor immediately if you develop a persistent cough, night sweats, or unexplained weight loss.

Posterior Reversible Encephalopathy Syndrome (PRES): A rare but serious brain condition. Symptoms include sudden severe headache, confusion, vision changes, and seizures. This is a medical emergency — call 911 immediately if these symptoms occur.

Serious allergic reactions (anaphylaxis/angioedema): Signs include swelling of the face, lips, tongue, or throat; trouble breathing; rapid heartbeat; or severe rash. Seek emergency care immediately.

Increased cancer risk: Malignancies (including non-melanoma skin cancer) occurred in 0.5% of Stelara-treated patients in clinical trials (0.64 events per hundred patient-years). Your doctor will monitor your skin during treatment, especially if you have a history of skin cancer.

Latex allergy reaction: The needle cover of the Stelara prefilled syringe contains dry natural rubber (latex). If you are latex-sensitive, tell your doctor before starting Stelara.

When to Call Your Doctor (Non-Emergency)

Mild fever that persists for more than 24 hours

Signs of a urinary tract infection (burning, frequent urination)

Skin changes, new moles, or unusual growths — especially important with Stelara's associated skin cancer risk

Worsening of your underlying condition (psoriasis flare, IBD flare, or joint pain increase)

If you are pregnant or planning to become pregnant

When to Call 911 or Go to the Emergency Room

Sudden severe headache, confusion, vision problems, or seizures (possible PRES)

Swelling of face, throat, tongue; difficulty breathing (anaphylaxis)

Signs of severe infection: high fever (above 103°F), confusion, severe shortness of breath

Vaccines and Stelara: What You Need to Know

Because Stelara weakens your immune system, you should not receive live vaccines during treatment. Avoid the BCG vaccine for 1 year before starting and 1 year after stopping Stelara. Also avoid live influenza (nasal spray), MMR, varicella, and yellow fever vaccines. Talk to your doctor about which vaccines are safe — inactivated vaccines are generally permitted.

Also read: Stelara Drug Interactions: What to Avoid and What to Tell Your Doctor