Stelara (ustekinumab) is a biologic medication used to treat four immune-driven conditions: plaque psoriasis, psoriatic arthritis, Crohn’s disease, and ulcerative colitis. It works by blocking two specific immune signaling proteins that drive inflammation in the skin, joints, and gut. Here’s what each of those uses looks like in practice, how the drug works, and what to expect from treatment.
Conditions Stelara Treats
Stelara is FDA-approved for adults with moderate to severe plaque psoriasis, active psoriatic arthritis, moderately to severely active Crohn’s disease, and moderately to severely active ulcerative colitis. For children aged 6 and older, it’s approved for plaque psoriasis and psoriatic arthritis.
All four conditions share a common thread: the immune system attacks the body’s own tissues. In psoriasis, that means skin cells. In psoriatic arthritis, it’s the joints (often alongside skin symptoms). In Crohn’s disease and ulcerative colitis, the target is the lining of the digestive tract. Stelara isn’t a first-line treatment for mild cases. It’s typically prescribed when the condition is moderate to severe and hasn’t responded well to other therapies, or when other treatments aren’t a good fit.
How Stelara Works
Stelara is a monoclonal antibody, meaning it’s a lab-made protein designed to latch onto a very specific target in the body. In this case, it binds to a protein subunit called p40, which is shared by two immune messengers: interleukin-12 (IL-12) and interleukin-23 (IL-23). These two proteins normally activate different branches of the immune system’s inflammatory response. By grabbing onto p40, Stelara prevents both IL-12 and IL-23 from docking with immune cells, which dials down the overactive inflammation driving all four conditions.
This dual-blocking approach is what distinguishes Stelara from biologics that target only one pathway. It binds equally well to IL-12, IL-23, and the p40 protein on its own, so neither signaling molecule can slip through.
How It’s Given and How Often
The dosing schedule depends on which condition you’re being treated for. For psoriasis and psoriatic arthritis, Stelara is given as a subcutaneous injection (a shot under the skin, similar to an insulin injection). You get the first two doses four weeks apart, then one dose every 12 weeks after that. Most adults receive 45 mg per dose, though people weighing over 220 pounds (100 kg) typically receive 90 mg.
Children aged 6 to 17 follow the same 12-week schedule, with dosing based on weight. Kids under 132 pounds receive a weight-calculated dose, while those above that threshold get the same flat doses as adults.
For Crohn’s disease and ulcerative colitis, treatment starts differently. The first dose is given intravenously (through an IV) at a clinic or infusion center, with the amount based on body weight. After that initial infusion, you switch to a subcutaneous injection of 90 mg every 8 weeks. The more frequent dosing for gut conditions reflects the higher level of inflammation Stelara needs to control in the digestive tract.
How Quickly Stelara Works
Most people notice some improvement within the first three to eight weeks, though the timeline varies by condition.
For plaque psoriasis, clinical trials measure results at 12 weeks using a scoring system that tracks skin clearance. At that point, 66% to 76% of participants achieved at least a 75% reduction in their psoriasis severity scores. Roughly 59% to 73% had their skin rated as clear or minimal. So for many people, meaningful skin clearing happens within the first three months, though improvement often begins earlier.
For Crohn’s disease, things can move a bit faster. By week 3, roughly 41% to 51% of patients in trials had a significant reduction in symptoms. By week 8, 21% to 40% had reached full clinical remission. The picture continued improving over time: at week 44, 47% of patients on Stelara were in remission and off corticosteroids, compared to 30% on placebo.
Ulcerative colitis results followed a similar arc. By week 8, 19% of patients achieved clinical remission (compared to 7% on placebo), and 58% experienced a meaningful clinical response. By week 44, those numbers climbed to 45% in remission and 74% with a clinical response.
Psoriatic arthritis tends to show a slower, steadier improvement. At 24 weeks, about 42% to 50% of patients achieved at least a 20% improvement in joint symptoms. Deeper responses (50% or 70% improvement) were less common but still occurred in a meaningful portion of patients.
Common Side Effects
Stelara’s side effect profile is relatively mild compared to many other immune-suppressing treatments. In psoriasis trials, the most frequently reported issues were common respiratory symptoms: nasopharyngitis (a stuffy or runny nose) occurred in about 8% of patients, and upper respiratory infections in about 5%. Headache, fatigue, and diarrhea each showed up in 2% to 5% of patients, rates that were similar to what people on placebo experienced.
For Crohn’s disease, the longer-term maintenance phase showed slightly different patterns. Nasopharyngitis was again the most common side effect at 11%, followed by redness at the injection site (5%), bronchitis (5%), itching (4%), and urinary tract infections (4%). During the initial IV infusion phase, the only side effect more common than placebo was vomiting, at 4%.
Because Stelara partially suppresses the immune system, infections are the main safety concern. The drug should not be given during an active infection or to anyone with active tuberculosis. You also cannot receive live vaccines while on Stelara, since a dampened immune system may not be able to handle even the weakened viruses in those vaccines. People with a known allergy to ustekinumab or any of the drug’s inactive ingredients should not use it.
What Treatment Looks Like Day to Day
One of the practical advantages of Stelara is its dosing frequency. For psoriasis and psoriatic arthritis, an injection every 12 weeks means you’re only thinking about treatment roughly four times a year after the initial loading doses. For Crohn’s disease and ulcerative colitis, the every-8-week maintenance schedule still means fewer than seven injections per year. Many people learn to self-inject at home using a prefilled syringe, which eliminates regular clinic visits for the maintenance phase.
The medication needs to be stored in a refrigerator. If you’re traveling or otherwise away from a fridge, planning ahead for proper storage is important to keep the drug effective.
Because Stelara lowers part of your immune response, you’ll want to stay aware of signs of infection, particularly respiratory illnesses and urinary tract infections. Your prescriber will typically screen for tuberculosis before starting treatment and may check periodically during therapy.