Stelara (ustekinumab) has a median half-life of about 19 days, meaning it takes roughly 3 to 4 months after your last dose for the drug to fully clear your system. That timeline can vary depending on your body weight, the condition being treated, and individual metabolism.
What the Half-Life Means in Practice
A drug’s half-life is the time it takes for half of it to leave your bloodstream. For Stelara, the FDA prescribing information reports a half-life ranging from about 15 to 46 days across clinical trials in psoriasis patients, with a median of approximately 19 days for people with Crohn’s disease and ulcerative colitis.
A drug is generally considered cleared after 4 to 5 half-lives. Using the 19-day median, that puts full elimination at roughly 76 to 95 days, or about 2.5 to 3 months. If your personal half-life falls on the longer end of the range, traces could linger for 4 months or more. There’s no simple blood test your doctor would routinely order to confirm it’s gone, but these pharmacokinetic estimates give a reliable window.
Why the Timeline Varies
Body weight is one of the biggest factors. Clinical data show that heavier patients tend to have lower blood concentrations of Stelara at any given dose, which reflects faster clearance relative to body size. This is part of the reason higher-weight patients are prescribed larger doses. Your individual clearance rate also depends on whether you’ve developed antibodies to the drug, which can speed up how quickly your body breaks it down.
The route of your most recent dose matters too. For inflammatory bowel disease, the first dose is typically given intravenously, producing peak blood levels around 125 mcg/mL. Subsequent subcutaneous (under-the-skin) injections produce much lower steady-state trough levels of about 2.5 mcg/mL. So the IV loading dose starts from a much higher concentration, but the half-life itself remains similar regardless of how the drug was delivered.
Timing for Surgery
If you’re planning elective surgery, your care team will likely want you to skip at least one scheduled dose before the procedure. For patients on a 12-week dosing schedule (common for psoriasis and psoriatic arthritis), UK perioperative guidelines recommend scheduling surgery at least 12 weeks and one day after your last injection. That ensures one full dosing interval has passed, lowering infection risk while the drug’s immune-suppressing effects fade.
For surgeries considered especially high infection risk, some guidelines suggest stopping 3 to 5 half-lives before the procedure, which translates to roughly 2 to 3.5 months using the 19-day median. Interestingly, for IBD-related surgeries, the recommendation is often to continue Stelara, since the risks of a disease flare may outweigh the infection risk from the drug.
Timing for Vaccines
Live vaccines (such as MMR, the nasal flu spray, or the yellow fever vaccine) should not be given while Stelara is still active in your system. Prescribing guidance recommends waiting at least 15 weeks after your last dose before receiving any live vaccine, and you can resume Stelara at least 2 weeks after vaccination. That 15-week window accounts for the drug’s long half-life and the time needed for your immune system to recover enough to safely handle a live virus or bacteria.
Inactivated vaccines (like the standard flu shot or COVID vaccines) are generally fine to receive while on Stelara, though your immune response to them may be somewhat blunted.
How Stelara Works in the Body
Stelara is a monoclonal antibody, essentially a lab-made protein designed to block two specific immune signaling molecules called IL-12 and IL-23. These molecules share a common building block (called p40), and Stelara binds to that shared component. By neutralizing both signals, it dials down the overactive immune pathways that drive psoriasis, psoriatic arthritis, Crohn’s disease, and ulcerative colitis.
Because it’s a large protein rather than a small chemical molecule, your body breaks it down slowly, the same way it would process any other antibody. This is why the half-life is measured in weeks rather than hours, and why its effects persist well beyond your last injection.
Clearance During Pregnancy and in Infants
Stelara can cross the placenta, particularly during the third trimester, which means infants born to mothers who used the drug during pregnancy will have detectable levels at birth. Data from the World Gastroenterology Organisation show that 74% of exposed infants had undetectable Stelara levels by six months of age, with a mean clearance time of about 6.7 months. This is considerably longer than the adult clearance timeline because infant metabolism handles these large antibody molecules differently. Live vaccines for the infant are typically delayed until the drug is confirmed cleared.