Tirzepatide half-life and steady state
5 days modelled half-life, peaking 24 h after a dose. What that means for how long it lasts, how much it builds up, and when bloodwork is worth drawing.
- Also known as
- Mounjaro, Zepbound
- Class
- GLP-1 / Metabolic
- Modelled half-life
- 5 days
- Time to peak
- 24 h
- Formulation
- Aqueous (reconstituted powder)
- Cleared per dosing interval
- 62% gone, 38% still present after 7 days
- Time to steady state
- ~25 days (about five half-lives)
- Accumulation at that cadence
- 1.61× a single dose
- Peak-to-trough at steady state
- 2.25×
- Regulatory status
- FDA APPROVED for T2 diabetes (Mounjaro) and obesity (Zepbound). Off-label for general weight loss.
- Monitoring panel
- Same as Semaglutide. HbA1c, fasting glucose, lipids, weight monthly.
- Before mixing
- Sealed powder tolerates room temperature in transit, but keep it refrigerated at 2–8 °C (36–46 °F) for anything beyond a few weeks, or frozen for months. Keep it dark — the carton it shipped in is doing a job.
- After mixing
- Once reconstituted with bacteriostatic water: refrigerate at 2–8 °C and use within about 28 days. The benzyl alcohol in bacteriostatic water is what buys that window — plain sterile water has no preservative, so a vial mixed with it should be treated as one sitting only. Kits are usually ten vials: only the one you mixed is on that 28-day clock — the sealed ones keep their own, much longer shelf life, so store them as powder, not as solution.
- What ruins it
- Do not freeze a reconstituted vial. Repeated freeze–thaw is one of the more reliable ways to degrade a peptide.
- Handling caveat
- General handling practice for this formulation. Your supplier’s own insert or COA overrides anything here.
Tirzepatide's modelled half-life of about five days is shorter than semaglutide's week, and that difference is worth more attention than it usually gets. Weekly dosing against a five-day half-life accumulates less — the plateau arrives sooner, around three to four weeks — and the level swings slightly more between injections. Neither difference is dramatic, but it means the two drugs are not interchangeable on a curve even though both are once-weekly.
Tirzepatide is a single peptide acting at two receptors, GIP and GLP-1, and its persistence comes from the same engineering strategy as semaglutide's: a fatty-acid chain that keeps it bound to albumin and out of the kidney's reach. Because one molecule does both jobs, there is one curve rather than two — the GIP and GLP-1 effects rise and fall together, which is not obvious from a mechanism description that lists them separately.
The practical consequence of a five-day half-life is at the top of the dose range rather than the bottom. At 15 mg a week the volume drawn is large, and the plateau is reached within a month of each titration step — so tolerability at a new step is knowable within weeks rather than being a slow surprise. The approved four-week interval between steps is therefore comfortably longer than the pharmacokinetics require, which tells you the titration is pacing side effects, not accumulation.
One dose
pkCurve function — a
one-compartment absorption-and-elimination model with the absorption rate fitted so the
peak lands at the published time to peak.Dosed once weekly
Charted at once weekly because that is the approved schedule for both of its indications. It is what the numbers below are indexed to, not a recommendation about frequency — that is a prescribing decision.
The arithmetic behind those numbers
fraction left after one interval = 2^(−1.40) = 0.379
accumulation ratio = 1 ÷ (1 − 0.379) = 1.61
time to steady state ≈ 5 × half-life = 25 days
peak-to-trough = simulated, 1.644 ÷ 0.7315 = 2.25
The accumulation ratio is a closed form; the peak-to-trough figure is not. The generator adds up enough repeated curves for the total to stop changing, then reads the highest and lowest points of the last interval — which is what steady state means in practice. The vertical axis is relative, not a concentration: the shape and the ratios carry across people, the absolute levels do not.
Interaction rules that name Tirzepatide
From the app's own interaction data. Not exhaustive, and not a safety clearance — a combination that is not listed is one nobody has documented here, which is not the same as one that is fine. The full combination checker has the rest.
Never Combine GLP-1 Agonists
Combining two GLP-1 or dual GLP-1/GIP agonists dramatically increases risk of severe GI side effects, pancreatitis, and offers no additive benefit. Choose one.
What to watch: Do not combine. If switching agents, wash out first GLP-1 before starting the second.
GLP-1 + Testosterone — Essential Muscle Preservation
Same as semaglutide — tirzepatide's superior fat loss effect also means superior muscle loss risk without testosterone support. TRT-dose testosterone is strongly recommended alongside any GLP-1 agent.
What to watch: Body composition (DEXA preferred), Total T, HbA1c, fasting glucose, lipids.
T3 + GLP-1 — Powerful Fat Loss Combination
T3 and GLP-1 agents both reduce body fat via complementary mechanisms. T3 increases basal metabolic rate; GLP-1 reduces appetite. Combined, they can produce significant fat loss. Add testosterone to prevent muscle loss in this combination.
What to watch: Heart rate, body weight weekly, Free T3 to avoid hyperthyroidism, fasting glucose.
Metformin + Tirzepatide — Additive Metabolic Benefits
Same as metformin + semaglutide — complementary mechanisms with additive glucose-lowering and weight loss benefits. Combination used in clinical practice for T2 diabetes management.
What to watch: HbA1c, fasting glucose, weight, GI tolerance, B12 levels.
Never Combine GLP-1 Class Agents
Retatrutide and tirzepatide both target GLP-1 receptors. Combining any two GLP-1/GIP/glucagon receptor agonists dramatically increases pancreatitis risk, severe GI events, and provides no additive weight loss benefit beyond one agent at maximum dose.
What to watch: Amylase, lipase if any abdominal pain. Do not combine.
The dosing rows this cadence came from
Established clinical use Reproduced from the app's entry so you can see what the chart above is indexed to. Which row applies to a particular person, if any, is a clinical decision this page does not make.
| Label | Amount | Route and frequency |
|---|---|---|
| Starting | 2.5mg/week | Weekly SubQ |
| Maintenance | 5-10mg/week | Weekly SubQ |
| Maximum | 15mg/week | Weekly SubQ |
When to draw bloodwork
The panel the app records for Tirzepatide is: Same as Semaglutide. HbA1c, fasting glucose, lipids, weight monthly.. The pharmacokinetic point is the timing rather than the list: after any change, a level takes about 25 days to settle, so a panel drawn sooner measures something still moving. And because the peak-to-trough swing here is 2.25×, when in the interval you draw changes the result materially — a result without a stated draw time relative to the last dose is hard to compare with anything. Whether a result means anything is a question for the clinician who ordered it, read against the reference range your own lab printed. The lab-marker pages cover what the individual analytes measure.
Related: the interactive half-life calculator to try other cadences, and the Tirzepatide reconstitution calculator.
The app draws this curve from the doses you actually logged — your dates, your cadence — and projects seven days forward from the last one.
Save this dose to your log