Tirzepatide is a dual GLP-1/GIP receptor agonist FDA-approved as Mounjaro (diabetes) and Zepbound (obesity). It produced up to 22.5% body weight loss in the SURMOUNT trials, exceeding semaglutide. The dual agonist mechanism combines appetite suppression (GLP-1) with enhanced insulin sensitivity and lipid metabolism (GIP). Tirzepatide represents the bridge between single-agonist semaglutide and triple-agonist retatrutide.
Quick Start
Route
SubQ injection (weekly)
Start low
2.5 mg SubQ
Frequency
Once weekly
Timing
No fasting required
Starting dose. 2.5 mg — Weekly, titrating up
Any time of day, with or without food. Once weekly on the same day each week.
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Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
Tiered Protocols · lowest first
Conservative start
2.5 mg weekly, titrating up · SubQ injection (weekly) · Once weekly
human clinical trial · FDA Zepbound label titration
Strong delayed gastric emptying - reduce meal size during titration.
2.5 -> 5 -> 7.5 -> 10 -> 12.5 -> 15 mg
Weekly
Standard
Weight Management (Max Dose)
15 mg · SubQ · Weekly
human clinical trial · SURMOUNT-1 (Jastreboff et al. 2022, NEJM)
Maximum dose after months of titration; 10 mg is also a common maintenance target.
15 mg
Weekly
Reconstitution CalculatorU-100
050100u
Draw to
— units
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01
How it works
Tirzepatide activates both GLP-1 and GIP receptors. GLP-1 activation provides appetite suppression, slowed gastric emptying, and enhanced insulin secretion. GIP activation improves insulin sensitivity, enhances lipid metabolism in adipose tissue, and may improve beta-cell function. The dual mechanism produces superior weight loss and glycemic control compared to GLP-1-only agents.
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What to expect
Early
Days 1–7
Weeks 1-4: Appetite suppression during titration.
Mid
Weeks 2–4
Weeks 4-12: Consistent weight loss.
Later
Weeks 4–12
Months 3-12: Significant cumulative results.
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Evidence
HumanStrong
AnimalPresent
In-vitroPresent
Each reference below was re-fetched from its PubMed record, and the quoted sentence was
confirmed to appear in that abstract and to support the claim it sits under. Follow any of
them to read the source.
Exact-molecule evidence boundary: the live abstract reports the quoted finding for Tirzepatide; no broader inference is made.
The efficacy and safety of tirzepatide, a novel glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, in people with obesity are not known.
Evidence scope. Exact molecule wording appears in the quoted live sentence. Only the population/model, formulation, route, and outcome expressly stated there are supported.
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the
same as saying they are false — it marks where the evidence is missing.
Dose/route: 2.5 mg weekly, titrating up; SubQ injection (weekly); Once weekly. No selected live abstract sentence verified this complete regimen.
Mechanism as written in source JSON. No selected live abstract sentence verified the complete mechanism at the card formulation/route and relevant population/model.
Primary safety claim as written in source JSON. No selected live abstract sentence verified the complete safety claim for this exact formulation and route.
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The honest take
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Superior to semaglutide
SURPASS-2 showed tirzepatide superior to semaglutide 1mg for weight loss and HbA1c reduction. Confirmed.
22.5% weight loss
Supported
Confirmed in SURMOUNT-1 at 15 mg dose.
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Interactions & stacking
Two different questions: what is documented about running these together, and what is documented about drawing them into the same syringe. A good pharmacological partner can still have to be pinned separately.
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Pin alone. Tirzepatide must not share a syringe with anything else, whatever the pharmacology says.
PIN ALONE. GLP-1 class.
Documented together
BPC-157BPC GI healing may reduce GLP-1 nausea.
AOD-9604Dual appetite suppression + direct fat metabolism.
Keep separate
SemaglutideDo not stack GLP-1 agonists.
RetatrutideDo not stack GLP-1 agonists.
MetforminMonitor glucose.
Check any specific pair in the Stack & Interaction Checker, which answers both questions separately. Absence of a documented conflict is not evidence of safety.
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Side effects & safety
Commonly reported
Nausea
Diarrhea
Constipation
Decreased appetite
Less common & notes
Same GLP-1 class warnings: pancreatitis, gallbladder, gastroparesis, thyroid C-cell signal in rodents.
Oral contraceptives may be less reliable during dose initiation and escalation: delayed gastric emptying (GLP-1 / amylin) can reduce oral drug absorption - Tirzepatide carries an FDA label warning to use a backup or non-oral method for 4 weeks after starting and after each dose increase.
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Pharmacokinetics
Illustrative plasma concentration · 21 d
Half-life
120h
Peak · Tmax
24h
Elimination
600h
Bioavailability
~80%
SubQ
Duration of action
7 days
Supports weekly dosing; appetite suppression and glycemic control sustained between doses
Clearance
Enzymatic degradation and renal elimination (albumin-bound, slow turnover)
Storage. Pens: 21 days room temp. Compounded: 28 days 2-8C.
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Regulatory status
FDA-approved as Mounjaro and Zepbound. WADA prohibited under S4.
Put it to work
Calculate, log & track
Open Tirzepatide straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.