If you have Crohn’s disease that is not responding well to other medications, a doctor may prescribe biologic drugs. Common side effects of biologics include headache, fever, and pain around the injection site.

Crohn’s disease is a condition that can cause inflammation, swelling, and irritation in the lining of the digestive tract.

Biologics are prescription drugs that can reduce these symptoms. They work by targeting specific molecules in the body that cause inflammation.

Doctors often prescribe biologics to those with refractory Crohn’s disease or moderate to severe symptoms. Refractory Crohn’s refers to an active disease that does not respond or has stopped responding to standard treatment.

Biologic drugs can work to bring on remission quickly. During remission, those with Crohn’s usually find that inflammation and intestinal symptoms stop. Biologics may also be used long-term to help maintain periods of remission.

Woman sat on the floor with her eyes closed and hand on her head to depict a headache.Share on Pinterest
FG Trade/Getty Images

Biologics tend to have fewer serious side effects than other Crohn’s disease medications, such as corticosteroids, which suppress the entire immune system.

Still, there are certain side effects you should know about before taking a biologic medication.

Some common side effects of biologics include:

  • redness, itching, bruising, pain, or swelling around the injection site
  • headache
  • fever or chills
  • difficulty breathing
  • low blood pressure
  • hives or rash
  • stomach pain
  • back pain
  • nausea
  • cough or sore throat

The type of biologic a doctor suggests will depend on the severity of your symptoms and the location of the disease. Everyone is different. A certain biologic drug may work better for some than others. You may have to try a few medications before finding what works for you.

The FDA has approved several biologic drugs to treat Crohn’s disease.

Biologic therapies for Crohn’s disease fall into three categories: anti-tumor necrosis factor (anti-TNF) therapies, interleukin inhibitors, and anti-integrin antibodies.

Anti-TNF therapies

Anti-TNF therapies work by targeting a protein that causes inflammation. For Crohn’s disease, they block inflammation caused by this protein in the intestines.

Examples of anti-TNF medications used in the treatment of Crohn’s include:

  • adalimumab (Humira, Exemptia)
  • certolizumab pegol (Cimzia)
  • infliximab (Remicade, Remsima, Inflectra)

Interleukin inhibitors

Interleukin inhibitors work similarly by blocking naturally occurring proteins that cause inflammation in the intestines.

A common example of an interleukin inhibitor used as a treatment for Crohn’s is ustekinumab (Stelara).

Anti-integrin antibodies

Anti-integrins work by blocking the immune system cells that cause inflammation.

Examples of anti-integrins used in the treatment of Crohn’s include:

  • natalizumab (Tysabri)
  • vedolizumab (Entyvio)

Biologics are typically given either subcutaneously (with a needle through the skin) or intravenously (through an IV tube). Depending on the medication, they may be given every 2–8 weeks. In most cases, you will need to go to a hospital or clinic to receive these treatments.

Step-up vs. top-down treatment

Biologic therapies can be a powerful tool in treating and managing Crohn’s disease. There are two different approaches to biologic therapy:

  • Step-up therapy: This involves trying several other treatments before starting a biologic.
  • Top-down therapy: This involves starting the biologic medications much earlier in the treatment process. This is now the preferred approach in many cases of moderate to severe Crohn’s disease.

However, different approaches may work better for different people depending on the severity and location of the disease.

Was this helpful?

Biologics may not be safe for everyone. Consider speaking with a doctor if you have tuberculosis (TB), are prone to infections, or have a heart condition.


Biologic drugs used for Crohn’s disease can increase the risk of reactivating a TB infection in people who have been exposed. TB is a serious, infectious lung disease.

A doctor should test you for TB before starting therapy with a biologic. A TB infection can be dormant in the body. Some people who’ve been exposed to the disease might not be aware of it.

If you’ve had prior exposure to TB, a doctor may recommend TB treatment before taking a biologic.


Biologics can lower the body’s ability to fight other infections by reducing your immune response. If you’re prone to infections, a doctor may suggest a different type of therapy.

If you are taking biologics, there is a high risk that the drug can reactivate hepatitis B. If you have previously had a hepatitis B infection and need to take biologics, a doctor can place you on antiviral medications to ensure the infection does not return.

Heart conditions

For people with certain heart conditions, such as heart failure, anti-TNF medications may increase the risk of the condition worsening. Heart failure is when the heart can’t pump enough blood to meet the body’s needs.

You should speak with a doctor as soon as possible if you experience shortness of breath or swelling of the feet while taking a biologic for Crohn’s disease. These may be signs of heart failure.

Other issues

Biologic therapies have occasionally been linked with serious health problems. In people taking biologic drugs, the following health problems are rarely reported:

  • certain blood disorders (bruising, bleeding)
  • neurological problems (including numbness, weakness, tingling, or visual disturbances, such as blurred vision, double vision, or partial blindness)
  • lymphoma
  • liver damage
  • severe allergic reactions

If you have Crohn’s disease, a doctor can help determine the best therapy for your individual needs.

Are biologics safe?

Biologics may not be safe for everyone. They can worsen certain existing health conditions, such as tuberculosis (TB) or infections. A healthcare professional can help determine the most suitable treatment options for you.

Can biologics make you tired?

Biologics may cause you to feel tired or low in energy. Studies have found that this is common both during the administration of the drug and directly after.

Can biologics cause weight gain?

Biologics can cause weight gain in some people. This may occur as the drug helps your bowels heal, allowing you to absorb more nutrition. Research suggests that these side effects occur more frequently in men.

Crohn’s disease is a chronic health condition that can cause inflammation and irritation in the lining of the digestive tract.

If your symptoms are not responding well to other medications or are severe or worsening, a doctor may consider prescribing biologic drugs.

Biologics work by targeting specific molecules in the body that cause inflammation. Like with all medications, biologics can cause some side effects. These include pain around the injection site, nausea, headache, and stomach pain.

If you have Crohn’s disease, a doctor can help determine the best treatment option for your individual needs.