What You Need to Know About Adalimumab Side Effects

Adalimumab — the active ingredient in Humira and more than 10 biosimilar versions — is a powerful biologic medication used to treat autoimmune conditions like rheumatoid arthritis, Crohn's disease, psoriasis, and more. Like all medications, it comes with potential side effects. Most are mild and manageable, but some are serious and require immediate medical attention.

This guide covers the side effects listed in FDA labeling so you know exactly what to watch for.

What Is Adalimumab?

Adalimumab is a TNF inhibitor — a type of biologic that works by blocking tumor necrosis factor-alpha (TNF-α), a protein that drives inflammation in autoimmune diseases. It's given as a subcutaneous injection, typically every other week. For a full overview, see our guide on what adalimumab is and how it's used.

Common Side Effects

These side effects are reported frequently in clinical trials and are generally mild to moderate:

• Injection site reactions — redness, swelling, itching, or pain at the injection site. This is the most common side effect, affecting up to 20% of patients. It usually improves over time.
• Upper respiratory infections — cold-like symptoms including sore throat, runny nose, and congestion
• Headache
• Rash
• Nausea
• Back pain
• Urinary tract infections
• Abdominal pain
• Flu-like symptoms — fatigue, body aches, low-grade fever
• Sinusitis

Most of these side effects don't require stopping the medication. However, tell your doctor if any of them become bothersome or don't go away.

Serious Side Effects

Adalimumab carries a boxed warning — the FDA's most serious safety alert — for two major risks:

1. Serious Infections

Because adalimumab suppresses part of your immune system, it increases your risk of serious infections, including:

• Tuberculosis (TB) — including reactivation of latent TB. You must be tested for TB before starting treatment.
• Invasive fungal infections — such as histoplasmosis and coccidioidomycosis
• Bacterial sepsis
• Opportunistic infections — infections that take advantage of a weakened immune system

When to call your doctor: Contact your doctor immediately if you develop fever, chills, persistent cough, shortness of breath, weight loss, or any signs of infection.

2. Malignancy Risk

Lymphoma and other cancers have been reported in patients taking TNF blockers, including adalimumab. The risk appears higher in children and adolescents. Rare cases of hepatosplenic T-cell lymphoma — a rare and often fatal type of cancer — have been reported, particularly in young patients also taking azathioprine or 6-mercaptopurine.

Other Serious Side Effects

• Heart failure — adalimumab can cause new or worsening heart failure. Tell your doctor if you have a history of heart problems.
• Liver damage (hepatotoxicity) — symptoms include yellowing of the skin or eyes, dark urine, and severe fatigue
• Lupus-like syndrome — joint pain, rash on the cheeks, and shortness of breath that develops during treatment
• Demyelinating disorders — rare cases of multiple sclerosis and Guillain-Barré syndrome have been reported
• Blood disorders (cytopenias) — including pancytopenia and aplastic anemia. Watch for persistent fever, bruising, bleeding, or extreme paleness.
• Severe allergic reactions (anaphylaxis) — rare but possible. Seek emergency care for difficulty breathing, throat swelling, or severe rash after injection.

Side Effects in Specific Populations

Pregnancy

Adalimumab is classified as Pregnancy Category B — animal studies haven't shown harm, but there are no adequate studies in pregnant women. Use only if clearly needed, and discuss risks with your doctor.

Children

Adalimumab is approved for children as young as 2 for some conditions. However, the boxed warning specifically notes increased cancer risk in children and adolescents taking TNF blockers. Pediatric patients should be monitored closely.

Elderly Patients

Older adults may be at higher risk for infections while taking adalimumab. Your doctor may monitor you more frequently.

Breastfeeding

Adalimumab is excreted in breast milk at low levels. Discuss the risks and benefits with your doctor if you are breastfeeding or plan to.

How to Manage Common Side Effects

Here are practical tips for dealing with the most common issues:

Injection Site Reactions

• Let the pen or syringe reach room temperature (15–30 minutes) before injecting — cold medication stings more
• Apply an ice pack to the injection area for a few minutes before and after
• Rotate injection sites between your thigh and abdomen (at least 2 inches from your navel)
• Avoid injecting into skin that is bruised, red, or tender

Upper Respiratory Infections

• Practice good hand hygiene and avoid close contact with sick people
• Talk to your doctor about getting a flu shot (inactivated vaccines are safe; live vaccines are not)
• Stay hydrated and rest when you feel symptoms coming on

General Tips

• Keep all scheduled appointments so your doctor can monitor for serious side effects
• Get regular lab work as recommended — this helps catch liver problems, blood disorders, and infections early
• Tell every doctor you see that you take adalimumab, especially before any surgery

For more about how adalimumab interacts with other medications, see our guide on adalimumab drug interactions.

Final Thoughts

Adalimumab is an effective treatment for many autoimmune conditions, and most patients tolerate it well. The most common side effects — injection site reactions and mild infections — are manageable. But the serious risks, particularly infections and malignancy, are real and require ongoing monitoring.

The key is staying informed, keeping up with your lab work, and calling your doctor at the first sign of anything unusual. Don't let fear of side effects keep you from a treatment that could significantly improve your quality of life — just make sure you and your doctor are watching for them together.

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