Mounjaro steady state: how levels build over the first weeks
A single-dose estimate is the right tool for asking how much of last week's injection is left, but it understates your total levels once you have been on Mounjaro for several weeks. Tirzepatide accumulates before it stabilizes, and understanding that curve explains why the early weeks of treatment feel different from later ones.
Why levels build instead of resetting
With a roughly 5-day half-life against a 7-day dosing interval, each weekly injection arrives before the previous one has fully cleared. So instead of returning to zero each week, tirzepatide stacks: the leftover from week one adds to week two, which adds to week three. The body only stops accumulating when the amount cleared between doses finally equals the amount injected.
Reaching steady state
Tirzepatide reaches steady state after roughly 4 to 5 weeks of consistent weekly dosing. At that point, trough levels (the low point just before your next injection) run about 1.6 times higher than the trough after a single first dose. This is the pharmacological reason dose titration is gradual: prescribers raise the dose in steps so the body adjusts to each new steady-state level before the next increase.
What the calculator shows and does not show
This calculator models one isolated dose decaying on its own. If you have been injecting weekly for over a month, the true amount in your system is higher than a single-dose estimate, because it sits on top of the accumulated baseline. Use the single-dose view to gauge how last week's shot is fading, not to estimate your full steady-state level.
Not medical advice
This content is for informational purposes only. It is not a substitute for advice from a qualified healthcare professional and should not be used to make medication, dosing, or health decisions.