Tirzepatide (Mounjaro, Zepbound) is a dual GIP and GLP-1 receptor agonist with an elimination half-life of approximately 5 days — meaning half of each dose clears your system every 5 days[1]. This extended biological window, made possible by a C20 fatty diacid modification that binds reversibly to albumin, is why once-weekly subcutaneous injections maintain active compound levels across the full 7-day cycle. After roughly 4 to 5 weeks of consistent dosing, your levels reach steady state: a stable plateau approximately 2.1 times higher than your very first dose, where the compound entering your system each week precisely replaces what was cleared.
Tirzepatide: Halflife Labs records ~120h (5 days) for SC. Evidence classification: FDA-approved product or prescribing-label source. Source summary: FDA NDA 215866.
Limitation: This is a population-level source statement, not a measured concentration or individualized prediction. Scientific review is documented on this page; the limited reviewer scope is defined on the About page.
Stable record ID: hlc:tirzepatide · Page revision: 2026-05-31 · Open the primary source
Mounjaro half-life answer: Mounjaro contains tirzepatide, and tirzepatide has an elimination half-life of approximately 5 days. A simple five-half-life estimate is about 25 days after a final dose, but individual exposure and clinical decisions cannot be determined from that model alone. See the dedicated Mounjaro half-life page for the brand-specific answer.
| Parameter | Value | Source |
|---|---|---|
| Elimination Half-Life | ~5 days (120 h; mean 5.4 days) | [1] |
| Time to Peak (Tmax) | 8–24 h (median ~24 h) SC | [1] |
| Route of Administration | Subcutaneous injection | — |
| Plasma Protein Binding | >99% (albumin) | [1] |
| Time to Steady State | ~4 to 5 weeks (once-weekly dosing) | [2] |
| Accumulation at Steady State | ~2.1× | [1] |
| Full Clearance (5 half-lives) | ~25 days after last dose | Calculated |
| Standard Dosing Frequency | Once weekly | [1] |
| Data Quality | Human RCT — population PK modeling of 19 pooled Phase 3 trials | — |
Tirzepatide remains active in the body for approximately 25 to 30 days after the final dose, determined by its 5-day elimination half-life.
Tirzepatide has an elimination half-life (t½) of approximately 5 days — the time it takes for active plasma concentration to fall by 50%[1]. For everyday users tracking their cycle, this means that 5 days after each injection, roughly half of that dose is still circulating in your system. After 10 days, about one-quarter remains. After 25 days — 5 full half-lives — approximately 97% has cleared, and your body has effectively returned to its pre-protocol baseline.
This timeline has practical consequences for anyone adjusting their protocol, taking a treatment break, or planning surgery. It's not like a supplement you stop and immediately clear — tirzepatide's biological influence continues to shape appetite, energy, and metabolic rate for several weeks after the last injection. Knowing this curve eliminates the guesswork about when your system has actually reset.
| Half-Lives Elapsed | Time After Last Dose | Estimated % Remaining in Plasma |
|---|---|---|
| 1 | ~5 days | 50% |
| 2 | ~10 days | 25% |
| 3 | ~15 days | 12.5% |
| 4 | ~20 days | 6.25% |
| 5 — clinical clearance threshold | ~25 days | ~3% |
Because tirzepatide's plasma half-life describes clearance from the bloodstream while its biological effects are governed by GIP and GLP-1 receptor occupancy, the experienced effects (appetite control, satiety, energy regulation) may persist throughout — and then fade progressively over several days — rather than switching off abruptly. Users consistently notice the trough as a gradual return of hunger rather than a sudden shift.
Tirzepatide reaches steady-state concentration — meaning the amount entering your body perfectly balances the amount leaving it — after roughly 4 to 5 weeks of consistent weekly dosing.
Steady state (Css) is the pharmacokinetic equilibrium where each weekly dose replenishes exactly what was cleared from the previous one. For tirzepatide, because the 5-day half-life is shorter than the 7-day dosing interval, moderate accumulation occurs with each successive injection until this balance is reached — typically after 4 to 5 weeks[2].
At steady state, your trough concentration — the lowest level in your system, measured just before the next injection — is approximately 2.1 times higher than it was after your very first dose. This matters practically: the compound is not simply "wearing off and restoring" each week. It's building toward a stable, elevated baseline that supports more consistent appetite suppression and metabolic effects as the weeks progress.
Because steady-state accumulation causes compound levels to peak and valley predictably every week, using a precise tracking app is essential for visualizing your personal estimated concentration curve and timing injection windows accurately. The Halflife app models your plasma concentration based on the 5-day half-life — including trough levels, steady-state projection, and reorder alerts. On-device, no account required.
Download Halflife — Free on iOSThe days 5–7 energy or hunger shift directly corresponds to the pharmacokinetic trough — the weekly low point in tirzepatide concentration before the next injection.
Tirzepatide's plasma concentration peaks approximately 8 to 24 hours after each injection, then declines steadily with its 5-day half-life[1]. By days 5 through 7, concentrations have reached their lowest point for the week — often called the "pre-injection trough." For many users, this is when hunger begins to return, satiety feels weaker, and energy may dip before the next scheduled dose.
This is not a sign that your protocol isn't working. It is the predictable shape of every weekly cycle, governed entirely by the compound's half-life. At steady state (weeks 4 and beyond), the trough sits higher than in the early weeks — so this variability tends to improve as accumulation builds. The most effective way to understand and respond to this pattern is to see the actual curve: knowing your trough is expected on Saturday, for example, is very different from not knowing why you feel different every Saturday.
Because the trough lands predictably at days 5–7, users who inject on Sunday will typically experience the lowest levels on Friday and Saturday. Shifting the injection to Monday places the trough over the weekend, which may fit better with individual weekly routines. Neither timing is pharmacokinetically superior — the curve shape is identical. But aligning the trough with lower-demand days (lighter social schedules, less demanding workdays) is a practical adaptation many protocol users make once they can visualize their curve.
The ~5-day half-life of tirzepatide is almost entirely a result of its C20 fatty diacid modification — a 20-carbon fatty acid chain attached to the peptide backbone at lysine-20[2]. In plain terms: this chemical feature acts like an anchor, binding tirzepatide tightly to albumin, the most abundant protein in your bloodstream. Albumin is too large to be filtered by the kidneys, so while bound, tirzepatide is essentially "hiding" inside a large carrier molecule. This dramatically slows clearance — from the 2-minute half-life of natural GLP-1 to 5 full days.
A second modification — an aminoisobutyric acid (Aib) substitution at position 2 of the backbone — blocks the enzyme DPP-4 from rapidly breaking down the peptide. Without this, tirzepatide would be inactivated within minutes after injection, just like the GLP-1 your body naturally produces.
In practical terms: these two engineering decisions are what allow a single subcutaneous injection to remain pharmacologically active across an entire week. Without the fatty acid anchor and the DPP-4 block, you would need to inject tirzepatide multiple times per day to maintain any meaningful effect. The 5-day half-life is the engineered result of solving that problem.
Tirzepatide's plasma half-life describes how quickly it clears from your blood. Its biological effects — appetite suppression, gastric emptying delay, blood sugar regulation — are governed by how well GIP and GLP-1 receptors are being activated, which depends on concentration. At steady state, trough concentrations on days 5 through 7 remain high enough for meaningful receptor engagement, so biological effects persist continuously despite fluctuating levels[1]. The feeling of the trough is real, but it represents a relative decline from a higher steady-state baseline — not a drop to zero.
The 5-day half-life makes once-weekly dosing pharmacokinetically optimal: the 7-day dosing interval is long enough that levels don't accumulate to dangerous heights, yet short enough that trough concentrations remain therapeutically active throughout. This balance — governed purely by the half-life — is what allows weekly injections to provide continuous metabolic effects rather than peaks and crashes.
If a weekly tirzepatide dose is missed, plasma concentrations continue declining at the ~5-day half-life rate — roughly 12 to 13% per day after the scheduled injection time. A dose delayed by 2 days results in approximately 25% lower levels than the expected trough. Per FDA prescribing information for Mounjaro, a missed dose can be taken within 4 days; beyond 4 days, skip that dose entirely and resume your regular schedule at the next scheduled time[1]. Missing more than one week creates a meaningful gap in steady-state levels that typically requires several additional weeks to re-establish.
Tirzepatide has a half-life of approximately 5 days. Semaglutide has a half-life of approximately 7 days. Both support once-weekly dosing, but semaglutide's longer half-life produces a shallower weekly trough, meaning concentrations stay more stable across the full 7-day interval.
The practical consequence of this 2-day difference in half-life is visible in the weekly estimated concentration curve. With semaglutide's 7-day half-life — exactly matching the dosing interval — concentrations decline more gently toward the next injection, keeping the peak-to-trough ratio lower throughout the weeksee semaglutide profile. With tirzepatide's 5-day half-life, concentrations drop slightly further before the next weekly dose, which is why the days-5–7 trough experience tends to be more noticeable with tirzepatide than with semaglutide for some users.
Mechanistically, tirzepatide and semaglutide are fundamentally different regardless of their similar half-lives: tirzepatide activates both GIP and GLP-1 receptors simultaneously, while semaglutide is a selective GLP-1 agonist only. This dual-agonism is responsible for the differences in clinical outcomes independent of the pharmacokinetic comparison.
| Compound | Half-Life | Dosing Frequency | Receptor Target | Status |
|---|---|---|---|---|
| Tirzepatide (Mounjaro/Zepbound) | ~5 days | Once weekly | GIP + GLP-1 (dual) | FDA-approved NDA 215866 |
| Semaglutide (Ozempic/Wegovy) | ~7 days | Once weekly | GLP-1 (selective) | FDA-approved NDA 209637 |
| Retatrutide | ~6 days | Once weekly | GIP + GLP-1 + Glucagon | Phase 3 trial |
| Cagrilintide | ~7 days | Once weekly | Amylin receptor agonist | Phase 3 (combo studies) |
| Route | Half-Life | Bioavailability | Tmax | Notes |
|---|---|---|---|---|
| Subcutaneous | ~5 days | ~80% (estimated) | 8–24 h (median ~24 h) | Standard FDA-approved route |
| Intravenous | ~5 days | 100% | Minutes | Reference PK route; not approved for clinical use |
| Intramuscular | No published data | No published data | No published data | Not an approved route |
| Oral | No published data | No published data | No published data | Oral formulation not currently approved |
Tirzepatide is an FDA-approved prescription medication (NDA 215866 / NDA 217806) and is not included in standard WADA anti-doping panels or workplace substance abuse drug test panels. Standard immunoassay urine drug screens will not detect tirzepatide. Specialized liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays can detect tirzepatide in plasma and urine for research purposes, but this testing is not part of any routine panel. If subject to drug testing in any context, disclose all prescription medications including tirzepatide to the testing agency.
The Halflife app models your tirzepatide estimated concentration curve based on the 5-day half-life — showing trough timing, steady-state progression, and reorder alerts alongside 43 other compounds. Free on iOS. No account required.
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