Calculator

Tirzepatide half-life calculator and dose-level plotter

Updated by the GLP Ladder Editorial Team. Editorial policy.

Short answer

Tirzepatide's half-life is about 5 days, so ke = ln2 ÷ 5 = 0.1386 per day and 37.9% of the amount present remains a week later. Weekly doses build by R = 1 ÷ (1 − e^(−7ke)) = 1.6101× and reach about 97% of steady state after 5 half-lives (25 days). Modeled estimate, as of Oct 19, 2026.

Published ladders

Trial or label schedules as published, for modeling only.

Dosing tiers (up to 12)

Tier 1

Tier 2

Tier 3

Tier 4

Tier 5

Tier 6

Mark missed doses

Unchecked doses are modeled as not taken.

Peak amount
21.46 mg-eq
Stable window from
Day 147
Stable average
15.25 mg-eq
Accumulation R
1.61×
Tirzepatide: modeled relative amount for the FDA label ladder to 15 mgStep chart of weekly doses (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg) above a curve of the modeled amount in the body, peaking at 21.46 mg-equivalents in week 28. Weekly values are in the table below.stable window06.2512.518.7525mg-eq048121620242832weeks from start2.5 mg5 mg7.5 mg10 mg12.5 mg15 mg
  • Dose ladder: mg per dose for each tier
  • One tick per dose; an open circle is a missed dose
  • Modeled relative amount in mg-equivalents (F = 1), not plasma concentration
  • Stable window: weekly troughs change by under 5%

How the model works.

Day 190: 21.464 mg-eq modeled. Move the slider or hover the chart for the per-dose breakdown.

Weekly data table
Modeled amount by week, FDA label ladder to 15 mg, start Oct 19, 2026 (mg-equivalents)
WeekStartsDose mgPeakTroughAverage
1Oct 19, 20262.52.17601.506
2Oct 26, 20262.53.0430.9892.171
3Nov 2, 20262.53.3751.3632.422
4Nov 9, 20262.53.5011.5052.518
5Nov 16, 202655.7181.5594.06
6Nov 23, 202656.6092.5684.738
7Nov 30, 202656.9482.9514.995
8Dec 7, 202657.0773.0955.093
9Dec 14, 20267.59.2923.156.636
10Dec 21, 20267.510.1874.167.314
11Dec 28, 20267.510.5254.5427.571
12Jan 4, 20277.510.6544.6877.669
13Jan 11, 20271012.874.7429.212
14Jan 18, 20271013.7645.7529.89
15Jan 25, 20271014.1036.13410.147
16Feb 1, 20271014.2326.27910.245
17Feb 8, 202712.516.4476.33411.788
18Feb 15, 202712.517.3417.34412.466
19Feb 22, 202712.517.687.72612.723
20Mar 1, 202712.517.817.87112.821
21Mar 8, 20271520.0257.92614.364
22Mar 15, 20271520.9198.93615.042
23Mar 22, 20271521.2589.31815.3
24Mar 29, 20271521.3879.46315.397
25Apr 5, 20271521.4369.51815.434
26Apr 12, 20271521.4559.53915.448
27Apr 19, 20271521.4629.54715.453
28Apr 26, 20271521.4649.5515.455
29May 3, 2027—10.0033.8126.42
30May 10, 2027—3.791.4452.433
31May 17, 2027—1.4360.5470.922
32May 24, 2027—0.5440.2070.349

Math, parameters and sources: model card.

How the plotter models levels

Each dose is treated as a one-compartment, first-order absorption curve (the Bateman function), and the curves for every dose are added together. The rate of elimination comes from the half-life (ke = ln2 ÷ t½) and the rate of absorption is solved from the published time to peak. The result is a relative amount in mg-equivalents with bioavailability set to 1, which is why it is useful for comparing schedules and not for reading a blood level.

Model parameters and derived constants (one weekly dose interval, τ = 7 days)
Compoundt½ (days)tmax (h)ke (/day)ka (/day)RLeft after 7 d
Retatrutide6240.1155253.53711.80330.4454
Tirzepatide5240.1386293.31221.61010.3789
Semaglutide7360.0990212.151420.5

Published ladders preloaded

The preset buttons load schedules exactly as published. They are there so you can see what a trial or label schedule looks like on the curve; none of them is a recommendation.

Ladders available in this plotter, with their source
LadderSteps (mg, weekly)Weeks per stepSource
Tirzepatide FDA label ladder to 15 mg2.5 → 5 → 7.5 → 10 → 12.5 → 154DailyMed, Aug 28, 2026
Tirzepatide FDA label ladder to 5 mg2.5 → 54DailyMed, Aug 28, 2026

Reading the stable window

With a fixed weekly dose, each week's lowest point (the trough) rises less than the week before. The plotter shades the "stable window" from the first week in which two consecutive week-over-week trough changes are both under 5%. After any dose increase the climb restarts, so a titration ladder usually reaches its stable window only on the final step. A missed dose shows up as a dip in both the curve and the weekly table.

How to read a dose-level curve (Tirzepatide, 1 mg weekly for 10 weeks, modeled)
Annotated modeled curve for weekly tirzepatide: first peak, trough, accumulation, stable window and washout, keyed to the list below. 1 2 3 4 5
  1. First peak about 24 hours after the first dose (time to peak).
  2. Trough: the lowest point, just before the next weekly dose.
  3. Accumulation: each dose adds to what is left, so peaks and troughs climb toward about 1.61× a single dose.
  4. Stable window: from about day 21, the weekly trough changes by less than 5% from one week to the next.
  5. Washout: after the last dose the amount halves every 5 days.

Relative amount (mg-equivalents), not a blood level. Model and sources: model card.

Frequently asked questions

What is the half-life of tirzepatide?

FDA labels: Zepbound states approximately 5–6 days (pharmacokinetics section) and approximately 5 days (overdosage section); Mounjaro states approximately 5 days. The model uses 5 days. The plotter uses 5 days and a time to peak of 24 hours.

How long does tirzepatide take to reach steady state?

About 5 half-lives, or roughly 25 days at a constant weekly dose, reaches about 97% of steady state (1 − 2^−5 = 96.9%). Each dose increase restarts that climb toward a new plateau. The plotter marks a "stable window" when the weekly trough changes by less than 5% across two consecutive weeks.

How much tirzepatide is left after a week?

By elimination alone, e^(−7 × 0.1386) = 0.3789, so about 37.9% of the amount present at the start of the week remains at its end. That carry-over is why weekly doses accumulate by about 1.61× before levels flatten.

Is the plotter output a blood level?

No. It is a relative amount in mg-equivalents from a one-compartment model with first-order absorption and bioavailability set to 1. Real plasma concentrations depend on body size, absorption site and individual clearance. Use the curve to compare schedules, not to judge your own levels.

Is tirzepatide FDA approved?

Yes. FDA approved as Mounjaro (type 2 diabetes) and Zepbound (weight management, obstructive sleep apnea). Numbers on this page quote the FDA prescribing information; your prescriber sets your dose.

Sources

  1. ZEPBOUND (tirzepatide) injection, for subcutaneous use - Full Prescribing Information, Medication Guide and Instructions for Use (DailyMed SPL set ID 487cd7e7-434c-4925-99fa-aa80b1cc776b, version 40). U.S. National Library of Medicine (DailyMed) / Eli Lilly and Company, Aug 28, 2026. Accessed Oct 19, 2026.
  2. MOUNJARO (tirzepatide) injection, for subcutaneous use - Full Prescribing Information, Medication Guide and Instructions for Use (DailyMed SPL set ID d2d7da5d-ad07-4228-955f-cf7e355c8cc0, version 40). U.S. National Library of Medicine (DailyMed) / Eli Lilly and Company, Aug 27, 2026. Accessed Oct 19, 2026.

The curve and figures are a modeled relative amount in the body (mg-equivalents), not a blood level.

Printed from GLP Ladder. To recreate this result, open https://glpladder.com/tools/tirzepatide-plotter/

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