What Is Tirzepatide? Dosage, Half-Life & How to Track It
Also known as: Mounjaro · Zepbound · GIP/GLP-1 dual agonist
Tirzepatide is a dual GIP/GLP-1 receptor agonist — the compound in Mounjaro and Zepbound. Adding the GIP receptor to the GLP-1 mechanism tends to produce more weight loss and, for many, less nausea than a GLP-1 alone. Its ~5-day half-life supports once-weekly dosing, titrated 2.5 → 15 mg in 4-week steps. Prescription medication; educational information only.
What tirzepatide is and how it works
Tirzepatide is a 39-amino-acid peptide that activates two incretin receptors instead of one: GLP-1 (the target semaglutide hits) and GIP. Both are gut hormones involved in insulin release and appetite.
Hitting both is the whole design. Clinically it produces greater average weight loss than selective GLP-1 agonists, and there is a tolerability twist: GIP activation appears to dampen the nausea signal that pure GLP-1 stimulation creates, so many people report an easier ride than on semaglutide at comparable results. It is approved for type 2 diabetes (Mounjaro) and obesity (Zepbound) — same molecule, different label.
The head-to-head with semaglutide is worth reading on its own; link below.
Typical dosing & titration
The FDA titration ladder is 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg, holding each step four weeks. The 2.5 mg start is a tolerability dose, not a therapeutic target — most people don’t feel the full effect until higher rungs. Once weekly, same day each week.
For reconstituted vials, concentration depends on vial size and water:
| Vial | BAC water | Concentration | 1 unit (U-100) ≈ |
|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 25 mcg |
| 10 mg | 2 mL | 5.0 mg/mL | 50 mcg |
| 15 mg | 2 mL | 7.5 mg/mL | 75 mcg |
| 30 mg | 3 mL | 10 mg/mL | 100 mcg |
At 10 mg/mL (a 30 mg vial in 3 mL), every step from 2.5 to 10 mg fits inside a single 1 mL syringe — the reason that setup is popular. The calculator does this arithmetic for whatever vial you have.
Half-life & what it means for frequency
Tirzepatide’s half-life is about 5 days, with peak blood levels 8–72 hours after a shot and roughly 80% bioavailability. Like semaglutide, that long half-life means once-weekly dosing and a multi-week climb to steady state — doses accumulate rather than cycle cleanly, so a Monday dose hasn’t cleared by Wednesday.
Practically, that is why the label warns against dosing more often than every three days, and why restarting after a break of more than a few weeks means re-titrating from lower — the accumulation you’d built up is gone. The simulator makes the weekly rise-and-fall and the steady-state build visible.
What to track & common side effects
Side effects are mostly GI — nausea, constipation, sometimes fatigue — and they reset with each dose increase, peaking around days 2–5 after you step up, then fading. Nausea runs roughly 18% (diabetes dosing) to 29% (weight dosing). Going from 10 to 15 mg adds only about 1.4 points of average weight loss but noticeably more nausea, so “highest dose” isn’t automatically “best dose.”
Same as any GLP-class drug: protect muscle with protein and resistance training, and treat the trend — weight, waist, tolerance at each step — as the real signal. Which dose you are on and how it landed is the decision-driving data.
How to track Tirzepatide in Stackeddd
Log the weekly shot and your current rung on the ladder so each escalation is intentional — and so you can see how the last one landed before the next. Trend weight and waist rather than reading single days, and keep protein visible so lean mass survives the deficit. The blood-level simulator shows the accumulation that makes week 4 of a dose feel different from week 1.
Model it yourself · free, no account
Blood-Level Simulator
Model it yourself: pick tirzepatide, set your weekly dose, and watch levels build to steady state week over week — the same pharmacokinetic engine that runs inside the app.
Related compounds
Related reading: Semaglutide vs Tirzepatide: half-life, cadence, and what to track
Frequently asked questions
What is tirzepatide used for?
It is a dual GIP/GLP-1 receptor agonist prescribed for type 2 diabetes (Mounjaro) and obesity (Zepbound). It lowers appetite and improves glucose control by activating two incretin receptors at once.
What is the half-life of tirzepatide?
About 5 days, with peak levels 8–72 hours after injection. That supports once-weekly dosing and means blood levels accumulate over the first several weeks before reaching steady state.
How is tirzepatide titrated?
The label ladder is 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg, holding each step four weeks to limit GI side effects. The 2.5 mg start is for tolerability rather than full effect.
Is tirzepatide better than semaglutide?
On average tirzepatide produces more weight loss and, for many people, less nausea, because GIP co-agonism dampens the GLP-1 nausea signal. “Better” still depends on the individual, cost, and tolerance — see our full comparison.
This is educational information, not medical advice. Doses and protocols above reflect published references and community practice — protocol decisions belong with your prescribing physician. Generic names used throughout. How this reference is built & how the AI is tested →
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