A biologic infusion is a treatment where a medication derived from living cells is delivered directly into your bloodstream through an IV line. These medications, called biologics, are large, complex proteins that can’t be absorbed through the digestive system as a pill, so they need to be either injected or infused. Most infusion sessions last one to two hours, though some can range from 30 minutes to six hours depending on the specific drug and how your body responds.
How Biologics Differ From Standard Medications
Most medications you pick up at a pharmacy are small-molecule drugs, meaning they’re built from simple chemical reactions in a lab. Biologics work differently. They’re extracted from living organisms, typically engineered from human or animal cells grown in controlled environments. This makes them far larger and more structurally complex than a typical pill.
Because of their size, biologics can’t pass through the lining of your gut intact. That’s why they’re given as IV infusions or, in some cases, as injections under the skin. The IV route allows the full dose to enter your bloodstream immediately, which is why many of the most powerful biologics are administered this way in a clinical setting rather than at home.
Conditions Treated With Biologic Infusions
Biologic infusions are most commonly used for autoimmune conditions, where the immune system mistakenly attacks the body’s own tissues. The major conditions include rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis (a type of inflammatory spinal arthritis), Crohn’s disease, ulcerative colitis, plaque psoriasis, and lupus. They’re also used for certain types of vasculitis, where blood vessels become inflamed, and for systemic sclerosis, a condition that causes hardening of the skin and connective tissues.
These drugs work by targeting specific parts of the immune system. Some block a protein called TNF-alpha that drives inflammation. Others deplete certain immune cells or interrupt the signaling pathways that trigger flare-ups. This precision is what makes biologics effective for people who haven’t responded to conventional treatments.
Screening Before Your First Infusion
Because biologics suppress parts of your immune system, your doctor will run several tests before clearing you for treatment. The most important screen is for tuberculosis. Even a latent TB infection, one that causes no symptoms, can reactivate when the immune system is dialed down. You’ll typically get a blood test along with a chest X-ray to rule this out.
Hepatitis B screening is also standard. Biologic therapy can trigger a dormant hepatitis B infection to flare, sometimes causing serious liver damage. The blood work checks for active infection, past exposure, and whether you have protective antibodies. If you lack immunity, vaccination before starting treatment is strongly recommended, and if active hepatitis B is found, antiviral therapy needs to begin weeks to months before the biologic can safely start. Screening for hepatitis C and HIV is also common practice.
What Happens During an Infusion Session
You’ll check in at an infusion center, which may be in a hospital, a standalone clinic, or your doctor’s office. A nurse will place a peripheral IV, usually in your arm. About 13% of patients report that finding a good vein takes more than one attempt, so drinking plenty of water the day before your appointment helps. Aim for at least 64 ounces. Hydration increases blood volume and makes veins easier to access.
Once the IV is placed, the medication is infused slowly. For your first session, the rate is often started low and gradually increased to watch for any reaction. A nurse monitors you throughout the process, checking your vital signs at regular intervals. This professional monitoring is something patients consistently value. In one study of people receiving biologic infusions for conditions like Crohn’s disease, rheumatoid arthritis, and psoriasis, 98% cited having trained staff present as the top advantage of infusion therapy.
After the infusion finishes, you’ll stay for an observation period so the care team can confirm you’re tolerating the drug well before you head home. Plan to bring something to pass the time: a book, headphones, or a laptop. About 41% of patients in research surveys said the infusion takes longer than they’d like, so being prepared makes a real difference in how the experience feels.
How Often You’ll Need Infusions
The schedule depends entirely on which biologic you’re receiving. Most follow a loading phase where infusions are closer together at the start, often at weeks zero, two, and six. After that, maintenance infusions typically fall every four to eight weeks, though some drugs are dosed every 12 weeks or longer. Your doctor will set a schedule based on the specific medication and how well your condition responds.
Possible Side Effects and Reactions
The most immediate concern during an infusion is an infusion reaction. Mild reactions are the most common and include skin flushing, itching, and hives, which occur in up to 90% of people who have any reaction at all. Respiratory symptoms like wheezing or shortness of breath happen in roughly 40% of reaction cases, and drops in blood pressure occur in about 30% to 35%.
Some people also experience fever, headache, nausea, or abdominal cramps. These symptoms typically appear during the infusion or within the first few hours afterward. Severe allergic reactions, including difficulty breathing, dizziness, and loss of consciousness, are rare but possible, which is exactly why infusions are given in a monitored setting with trained staff ready to intervene.
The longer-term risk to be aware of is increased susceptibility to infections. Because biologics suppress immune activity, your body becomes less effective at fighting off bacteria, viruses, and fungi. This is why the pre-treatment screening for TB and hepatitis is so important, and why your care team will monitor you for signs of infection throughout your treatment.
Cost of Biologic Infusions
Biologics are among the most expensive medications available. For plaque psoriasis alone, the average annual treatment cost reached $47,125 in 2021, up from about $21,000 in 2007. Individual drugs vary widely: annual costs in 2021 ranged from roughly $12,400 on the low end to over $70,000 for newer options. Research suggests that if patients started on the lowest-cost biologic in each drug class, the average annual cost could drop by about 44%.
Most people don’t pay these full amounts out of pocket. Insurance typically covers biologic infusions for approved conditions, though copays and coinsurance can still be significant. Most manufacturers offer patient assistance programs that reduce or eliminate copays for eligible patients. Your prescribing doctor’s office or the infusion center can usually help you navigate these programs before your first appointment.