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

Kevzara (sarilumab) is a powerful biologic medication that works by blocking the IL-6 receptor in your immune system. This mechanism effectively reduces inflammation—but it also means your immune system is somewhat suppressed, which comes with risks. Understanding what side effects to expect and which ones require immediate medical attention is essential for safe Kevzara use.

Kevzara's Boxed Warning: Serious Infections

The FDA requires Kevzara to carry a Boxed Warning—the most serious type of warning the FDA issues—for the risk of serious infections. Because Kevzara suppresses part of your immune system, it can lower your body's ability to fight infections. Serious and sometimes fatal infections have been reported in patients taking Kevzara, including:

Tuberculosis (TB) — both new and reactivated latent TB

Bacterial infections (most commonly pneumonia and cellulitis)

Invasive fungal infections (candidiasis, pneumocystis, and others)

Viral infections and other opportunistic infections

Your doctor will test you for latent tuberculosis before starting Kevzara. Do not start Kevzara if you have an active infection. Call your doctor or go to urgent care immediately if you develop fever, chills, unusual cough, body aches, burning with urination, or any signs of infection while on Kevzara.

Common Side Effects of Kevzara

In clinical trials, the most frequent side effects in Kevzara patients (occurring in at least 3% of patients) were:

Neutropenia (low white blood cell count) — This is the most common significant lab abnormality. It usually doesn't cause symptoms by itself, which is why regular CBC monitoring is required. Your doctor may reduce your Kevzara dose or pause treatment if your neutrophil count drops too low.

Elevated liver enzymes (ALT) — Liver enzyme elevations are common with Kevzara, especially if you're also taking methotrexate. This is monitored with regular blood tests. Clinical hepatic injury has not occurred in studies, but it requires monitoring.

Injection site reactions — Redness, swelling, bruising, or itching at the injection site are common, especially in the first weeks of treatment. Rotating injection sites can help.

Upper respiratory infections — Similar in frequency to placebo in most trials; includes common cold and mild upper respiratory illnesses.

Urinary tract infections — Somewhat more common in Kevzara users; see your doctor promptly if you have burning urination, frequency, or pelvic pain.

Elevated cholesterol and triglycerides — Kevzara can alter your lipid levels. Your doctor will check a fasting lipid panel at baseline and about 4–8 weeks after starting.

Serious Side Effects That Require Immediate Medical Attention

Gastrointestinal perforation: Tears in the stomach or intestine have been reported with Kevzara. Risk is higher in patients with diverticulitis or who take NSAIDs, corticosteroids, or methotrexate. Seek emergency care immediately if you have severe abdominal pain that doesn't go away, fever, or vomiting with abdominal pain.

Serious allergic reactions: Get emergency help right away if you develop shortness of breath or difficulty breathing, dizziness or fainting, swelling of lips, tongue, or face, severe abdominal pain, or chest pain.

Liver damage symptoms: Call your doctor if you develop yellowing of skin or eyes, dark urine, upper right abdominal pain, or unusual fatigue—these may signal serious liver injury.

Cancer risk: Kevzara may increase your risk of certain cancers by changing how your immune system works. Tell your doctor about any personal or family history of cancer before starting Kevzara, and report any new lumps, unexplained weight loss, or night sweats.

Lab Monitoring Required While on Kevzara

Regular blood tests are required to safely continue Kevzara therapy:

CBC with differential (neutrophil and platelet counts): at baseline, 4–8 weeks after starting, then every 3 months

Liver function tests (ALT/AST): at baseline, 4–8 weeks after starting, then every 3 months

Fasting lipid panel: at baseline and 4–8 weeks after starting

Important Safety Precautions While on Kevzara

Do not receive live vaccines while on Kevzara (this includes live flu shots, yellow fever, live shingles vaccine Zostavax, and MMR). The inactivated/recombinant shingles vaccine Shingrix is acceptable.

Tell every healthcare provider you see that you are taking Kevzara. Consider carrying an immunosuppression alert card.

Do not start Kevzara if you have an active infection—even a minor one. Discuss with your rheumatologist before resuming if you develop an infection while on treatment.

For a complete look at drug interactions with Kevzara, see our article on Kevzara drug interactions.