Tirzepatide Dosage, half-life & reference guide
Also known as Mounjaro · Zepbound · LY3298176
The first dual GIP/GLP-1 receptor agonist: it activates two gut-hormone pathways at once, and in a head-to-head trial it produced more weight loss than semaglutide (20.2% vs 13.7% at 72 weeks).
- FDA label
- 2.5–15 mgstarting dose 2.5 mg
- How often
- Weekly
- Half-life
- ~5 days
- Evidence
- ●●●
Established - Route
- SubQ injection
How it works.
Dual GIP/GLP-1 receptor agonist. Significantly reduces body weight through appetite suppression, slowed gastric emptying, and improved insulin sensitivity. Approved for T2DM and obesity management.
Commonly reported: Very strong appetite suppression and meals ending early, with nausea or tiredness for a day or two after the injection, mostly after dose increases. FDA-approved for diabetes (Mounjaro) and for weight management and sleep apnea (Zepbound).
Half-life & active level
The half-life of Tirzepatide is ~5 days (FDA label).
Here's how a typical Tirzepatide schedule accumulates over four weeks (one-compartment estimate).
An estimate from the half-life above, not a measurement. See your own curve build live in the half-life calculator.
Where Tirzepatide works.
Appetite & metabolism
In people. In a head-to-head trial it produced more weight loss than semaglutide (20.2% vs 13.7% at 72 weeks).
An area lights for what a peptide is used for and what people report, with the evidence beside it. It isn’t a promise that it works there.
Week by week.
What to expect in the first 8 weeks
- Onset
- Days–2 weeks
- Peak effect
- 72+ weeks
- Duration
- Ongoing
Day 1–28 · 2.5 mgRCT
Getting your gut acclimated
The 2.5mg run-in lets your gut adapt to GIP/GLP-1 signaling. Expect appetite to drop within days and some mild nausea in week 1–2. Don't expect weight loss yet — you're building tolerance for the real dose.
The science
The 2.5mg run-in is per FDA Zepbound labeling, there to limit GI side effects at higher doses. The GIP component eases nausea in animal studies; in the SURMOUNT-5 head-to-head, nausea rates matched semaglutide (44% each), but fewer people stopped for GI side effects over 72 weeks (2.7% vs 5.6%).
Sources- FDA Zepbound label (2024)
- Aronne et al. (2025)
Updated Sep 2026
Day 29–56 · 5 mgRCT
First therapeutic dose — weight drops
You're at 5mg — the first real therapeutic dose. Appetite suppression is fully online and you should start seeing clear scale movement. SURMOUNT-1's 5mg arm reached 15% at 72 weeks.
The science
Jastreboff 2022 (NEJM SURMOUNT-1) documented the 5mg arm reaching −15% body weight at week 72. "Food noise" reduction is commonly reported in this window — users describe not thinking about food between meals for the first time in years.
Sources- Jastreboff et al. (2022)
Updated Apr 2026
Any dayRCT
What Tirzepatide is built on
One of the most thoroughly trialed weight-loss drugs in history: SURMOUNT 1 through 5, a head-to-head win over semaglutide, and an FDA approval for obstructive sleep apnea added Dec 2024.
The science
Eli Lilly (Mounjaro for diabetes 2022; Zepbound for obesity 2023). SURMOUNT-OSA (Malhotra 2024 NEJM) expanded the FDA label for moderate-to-severe obstructive sleep apnea with obesity. SUMMIT 2024 showed tirzepatide reduces HFpEF worsening events — opening cardiovascular-outcome use cases beyond weight management.
Sources- Jastreboff et al. (2022)
- Aronne et al. (2025)
Updated Apr 2026
With BPC-157Community
Why people add BPC-157 to Tirz
GI side effects during Tirz titration can be rough, and BPC-157, first studied as a stomach-protecting peptide, is added to ease them. Commonly reported: smoother step-ups, especially the later ones.
The science
Mechanism fit: BPC-157 is a fragment of a "body protection compound" first isolated from human gastric juice and characterized as gastroprotective in animal studies (gut mucosal integrity, reduced NSAID damage, gut-brain axis modulation). Tirz nausea isn't caused by gastric damage, and no trial has tested the combination; the pattern comes from community reports.
Sources- Sikiric et al. (2018)
Updated Sep 2026
Any dayClinical
Protein + lifting decide what the loss is made of
Tirz may spare a bit more lean mass than GLP-1-only drugs, though that hasn't been tested head to head, and a meaningful share of any rapid loss is muscle. Keep protein around 1.6–2.2g/kg and keep training resistance through the cut. The appetite suppression handles intake; your protein and lifting decide whether the scale drop is fat or muscle.
The science
Across incretin body-composition data, roughly 25–40% of weight lost is lean mass; in SURMOUNT-1 about three-quarters of the loss was fat, the same share as placebo, and no trial has compared lean-mass sparing against pure GLP-1s head to head. Muscle-sparing add-on trials (apitegromab + tirzepatide, EMBRAZE: ~1.9kg less lean loss; bimagrumab + sema: ~92% of loss from fat) show the field moving, but none is standard care — protein and resistance training remain the available levers.
Sources- EMBRAZE (2025)
Updated Sep 2026
After week 8
Day 57–112 · 7.5 mgRCT
Dual agonism in full effect
Dual agonism is in full effect. Commonly reported: weight loss picking up pace and body composition shifting in a way people notice.
The science
SURMOUNT-1 participants in the 10mg arm reached approximately −19% at 72wk (Jastreboff 2022). Whether the GIP arm spares lean mass hasn't been tested head to head; SURMOUNT-5 compared weight and waist with semaglutide, not body composition.
Sources- Jastreboff et al. (2022)
- Aronne et al. (2025)
Updated Sep 2026
Day 113–168 · 12.5 mgRCT
Max titration reached
Max titration (12.5 → 15mg). Appetite suppression is strongest here, and 'food noise silence' is the most common subjective change. If nausea's rough, holding at 12.5 is a reasonable call.
The science
Zepbound prescribing info 2024 documents the GI discontinuation rate rising from 3.3% at 10mg to 4.3% at 15mg. SURMOUNT-1 15mg arm reached −22.5% at 72wk. Some users plateau at 10mg and never need to escalate — staying at the lowest effective dose is the community norm.
Sources- FDA Zepbound label (2024)
- Jastreboff et al. (2022)
Updated Apr 2026
Day 169–504RCT
Weeks 24 to 72: where most people plateau
Most people reach a weight plateau between about 6 and 9 months, and nearly 9 in 10 have plateaued by week 72; that is expected, not a sign it stopped working. In the SURMOUNT-5 head-to-head, tirzepatide reached 20.2% loss at 72 weeks against 13.7% for semaglutide, with nearly twice as many people crossing 25% loss.
The science
Aronne 2025 (NEJM SURMOUNT-5, 751 patients, 72wk): the first direct Tirz-vs-Sema comparison. Tirz arm hit 20.2% vs 13.7% for sema — ~47% greater relative loss — and ≥25% loss was reached by 31.6% on tirz vs 16.1% on sema. Stopping because of GI side effects: 2.7% vs 5.6%. A post-hoc analysis of SURMOUNT-1 found a median time to plateau of 24–36 weeks, with about 88–90% plateaued by week 72 (Horn 2025). SURMOUNT-OSA also showed ~25 AHI event reduction — which led to the Dec 2024 FDA approval for obstructive sleep apnea with obesity.
Sources- Aronne et al. (2025)
- Horn et al. (2025)
- Malhotra et al. (2024)
Updated Sep 2026
Day 365+RCT
A maintenance medication, not a course
Before deciding to stop, know the pattern: stopping tirzepatide usually means regaining most of the loss. A 2026 BMJ meta-analysis puts it around 10kg back in the first year and back to baseline in about 18 months, and in SURMOUNT-4 people switched to placebo regained 14% of their body weight within a year. Hold, slow-taper, or stop is a call for you and your clinician — go in expecting a long-term relationship, not a fixed course.
The science
SURMOUNT-4 (withdrawal design) and a BMJ meta-analysis (West 2026) document substantial regain after discontinuation (~9.9kg in year 1, back to baseline by ~1.5 years), reflecting that incretin therapy maintains a metabolic set point rather than resetting it. The continue/taper/stop decision is yours, made with your clinician.
Sources- SURMOUNT-4 (2024)
- West et al. (2026)
Updated Sep 2026
Day 1 is the day you start it.
SURMOUNT Phase III trials. FDA-approved. Head-to-head with semaglutide showing superior weight loss.
Clinical trial data
Mixing and a typical run.
Example numbers
Reconstitution example
Reconstitute a 10 mg vial of Tirzepatide with 2 mL of bacteriostatic water and a 2.5 mg dose is 50 units on a U-100 syringe, about 4 doses per vial.
- Vial
- 10 mg
- Water
- 2 mL
- Amount
- 2.5 mg
Draw to50 units
0.5 mL insulin syringe · 50 units
Run notes
- Cycle
- FDA-approved for ongoing use. Titrate slowly upward. Community maintains on minimum effective dose.Community practice — opinions vary. Not a clinical recommendation.
- Timing
- Once weekly SubQ. Consistent day and time preferred. Can take with or without food.
- Route
- SubQ injection
- Stacks
- BPC-157 (GI support), MOTS-c
Safety.
Common side effects
- Nausea
- Diarrhea
- Vomiting
- Constipation
- Abdominal pain
- Decreased appetite
- Fatigue
Interactions
Tirzepatide delays gastric emptying and can reduce the absorption of concomitant oral medications — the label specifically flags reduced oral-contraceptive efficacy, a documented interaction to discuss with a clinician. Co-use with insulin or insulin secretagogues (sulfonylureas) increases hypoglycemia risk per the label, warranting clinician-guided dose review and glucose monitoring. No specific documented interaction with SSRIs, anticoagulants, or thyroid replacement beyond general caution; raise all medications with your clinician.
Safety notes
Across the SURMOUNT program and the FDA Zepbound label, the dominant adverse events are gastrointestinal (nausea, diarrhea, vomiting, constipation), mostly mild-moderate and escalation-related. The label carries a boxed warning for thyroid C-cell tumors based on rodent studies (human relevance undetermined; contraindicated with personal/family history of medullary thyroid carcinoma or MEN 2). Trial-adjudicated acute pancreatitis was ~0.2% (similar to placebo); gallstones were ~1.1% vs 1.0% on placebo and gallbladder inflammation 0.7% vs 0.2%, partly attributable to rapid weight loss. These are trial/label findings to review with your clinician.
Goes with.
Questions people ask.
What is Tirzepatide?
The first dual GIP/GLP-1 receptor agonist: it activates two gut-hormone pathways at once, and in a head-to-head trial it produced more weight loss than semaglutide (20.2% vs 13.7% at 72 weeks).
How is Tirzepatide dosed in research?
The FDA label range for Tirzepatide is 2.5–15 mg, weekly, with a 2.5 mg starting dose.
How long does Tirzepatide last?
The half-life of Tirzepatide is ~5 days (FDA label).
What do people report on Tirzepatide?
Commonly reported on Tirzepatide: very strong appetite suppression and meals ending early, with nausea or tiredness for a day or two after the injection, mostly after dose increases. FDA-approved for diabetes (Mounjaro) and for weight management and sleep apnea (Zepbound).
Is Tirzepatide safe?
The research basis for Tirzepatide is established: clinical trials or FDA-approved use exists. Common side effects in the library: nausea, diarrhea, vomiting, constipation, abdominal pain, decreased appetite and fatigue.
What does Tirzepatide stack with?
Common stacks for Tirzepatide: BPC-157 (GI support) and MOTS-c. Curated stacks with Tirzepatide: Shred Stack.
Research.
Reference.
- Cadence
Weekly
- Half-life
~5 days
~5 days (FDA label)
- Research basis
●●●
EstablishedClinical trials or FDA-approved use exists
Track your progress
Watch it work.
Weight, waist and photos in one arc.
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