Your medicine level across the week
Tirzepatide has a half-life of about five days, so each weekly dose overlaps the last. After about four weeks the level settles: it rises for a day or two after each injection, then falls. The peak is roughly twice the low point.
For people already prescribed tirzepatide. This tool doesn’t recommend a dose.
The hatched band is when side effects are most likely, from about twelve hours after an injection to a few days later.
This is the average shape, not your exact levels. Body weight and how fast you clear the medicine change the height, not the shape.
How to read it
The scale stays fixed when you change the dose, so you can compare doses directly.
The shape is the same at every dose. Dose moves the line up or down, not which day is highest. That’s why dose doesn’t change the best injection day.
The chart shows a settled pattern. For about four weeks after starting or increasing a dose, the level is still building.
This is about drug levels, not about effectiveness
No one has published the level at which appetite suppression fades, and it will be different for different people — which is why low doses work for some and not others. This tool is designed to let you understand how the drug levels typically behave, from the research we have.
Sources and limits
Where these numbers come from
The curve uses Eli Lilly’s measurements, as published in the FDA’s clinical pharmacology review.
Tirzepatide has a half-life of about five days, peaks one to two days after injection, and settles after about four weeks. A 15mg dose peaks at about 1,990 ng/mL; other doses scale in proportion.
FDA Center for Drug Evaluation and Research, Clinical Pharmacology Review, application 215866, 2022. The peak and trough figures are from Table 6.
What we have assumed, and what this cannot tell you
Absorption is published as a range, so we use a value that matches the measured peak and low point. Treat the shape as reliable and the exact figures as approximate.
The measurements come from one study of 11 to 12 people per group.
Body weight changes the height of the curve: about 23% higher at 70kg and 21% lower at 120kg, compared with 90kg.
The shape is similar for most people, because it depends on the half-life.
Drug levels aren’t the same as how you feel. This chart can’t show when appetite effects fade.
For people already prescribed tirzepatide. It doesn’t recommend a dose or replace your prescriber’s advice. If you feel unwell, contact your doctor or NHS 111.