Peptide dosage calculator
Reconstitution math, draw units, and doses-per-vial for 23 peptides — defaults to Tirzepatide. Click any chip to switch compounds and see the exact U-100 mark in real time.
How to use this Tirzepatide dosage calculator
This Tirzepatide dosage calculator runs reconstitution math live for the research-format Tirzepatide vial sizes — 5mg, 10mg, 15mg, and 20mg lyophilized vials — and returns the exact mark to draw to on a 1mL U-100 insulin syringe. The defaults above (15mg vial, 3mL bacteriostatic water, 2.5mg target dose) match the standard Phase-3 starting titration and pull to the 50-unit mark on a U-100 syringe — the same 2.5mg dose that a Week-1 Mounjaro or Zepbound pen delivers, just drawn from a research vial instead.
Pick your Tirzepatide vial size
Research-format compounded Tirzepatide ships in 5mg, 10mg, 15mg, and 20mg lyophilized vials — the supplier presets above cover all four. The 15mg vial is the most common format at mid-titration (5–7.5mg weekly) because it yields a clean 30-day supply. The 20mg vial is the practical choice for users already titrated to 10mg+ weekly maintenance doses.
Pick your BAC water volume
Tirzepatide reconstitutes cleanly at 3mL of bacteriostatic water for a 15mg vial — a 5 mg/mL concentration where every titration step pulls to a clean U-100 mark (2.5mg = 50U, 5mg = 100U full syringe). The 10mg vial at 2mL BAC yields the same 5 mg/mL. The 20mg vial at 2mL BAC yields 10 mg/mL (halves every draw — useful for users already at 10mg+ maintenance to keep draws readable).
Set your Tirzepatide target dose
Tirzepatide is dosed in milligrams — switch the unit toggle to mg. The standard titration is 2.5 mg weekly for 4 weeks, then 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg (each step 4 weeks). Zepbound labeling caps at 15 mg; Mounjaro labeling caps at 15 mg for diabetes. Enter your current dose and the calculator returns U-100 units, injection volume, concentration, and doses per vial.
Read the U-100 syringe units
Pull the plunger to the indicated unit mark on a 1mL U-100 insulin syringe. At default settings (15mg/3mL/2.5mg dose), the draw is 50U — exactly half the syringe, the same active dose as a Week-1 Mounjaro or Zepbound pen click. The visual syringe above shows the fill in real time — drag it directly to scrub through titration steps.
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Tirzepatide dosage, reconstitution, and titration guide
Tirzepatide is Eli Lilly's dual GLP-1 / GIP receptor agonist, marketed as Mounjaro® (FDA-approved for type 2 diabetes, 2022) and Zepbound® (FDA-approved for chronic weight management, 2023). Both are pre-filled single-dose pens delivering the same molecule at the same doses (2.5 → 15 mg weekly). Research-format compounded Tirzepatide is the same peptide in lyophilized vial form, available through 503A compounding pharmacies during FDA-designated shortage periods. This guide covers Tirzepatide dose math, the full 2.5 → 15 mg titration schedule, reconstitution at 5mg / 10mg / 15mg / 20mg vial sizes, dosing in units, compounded vs Mounjaro vs Zepbound, the Tirzepatide vs Semaglutide comparison (the highest-volume question in the GLP-1 space), weight-loss results from the SURMOUNT trials (~21% body weight reduction at 15mg/72 weeks), and side effects.
Tirzepatide dosing schedule and titration
Tirzepatide uses a strict stepwise titration to manage gastrointestinal tolerability. The schedule below matches the FDA-approved titration for Mounjaro (diabetes) and Zepbound (weight loss) — they're identical. Doses are the standard clinical schedule, not medical recommendations.
| Titration week | Weekly dose | U-100 units (15mg/3mL vial) | Notes |
|---|---|---|---|
| Weeks 1–4 | 2.5 mg | 50U | Initiation — tolerability assessment, not therapeutic |
| Weeks 5–8 | 5 mg | 100U (full syringe) | First therapeutic dose |
| Weeks 9–12 | 7.5 mg | 150U (1.5 syringes) | First titration step |
| Weeks 13–16 | 10 mg | 200U (2 syringes) | Mid-range maintenance |
| Weeks 17–20 | 12.5 mg | 250U (2.5 syringes) | Higher-range maintenance |
| Weeks 21+ | 15 mg | 300U (3 syringes) | Max dose — SURMOUNT-1 21% weight loss arm |
Tirzepatide reconstitution — 5mg, 10mg, 15mg, 20mg vials
The 15mg lyophilized vial is the most common research Tirzepatide format at mid-titration. Reconstitution at 3mL of bacteriostatic water yields a 5 mg/mL concentration where every titration step pulls to a clean U-100 mark (2.5mg = 50U, 5mg = 100U). The 10mg vial at 2mL BAC yields the same 5 mg/mL. The 20mg vial at 2mL BAC yields 10 mg/mL — useful at high maintenance doses where 5 mg/mL draws would require multiple syringe fills. The 5mg vial with 1mL BAC yields 5 mg/mL and covers a 4-week starting titration.
Tirzepatide vs Semaglutide
Tirzepatide and Semaglutide are the two most widely used GLP-1 peptides but differ mechanistically. Semaglutide (Ozempic/Wegovy) is a GLP-1 receptor monoagonist — activates only the GLP-1 pathway. Tirzepatide is a dual agonist activating both GLP-1 and GIP receptors. The added GIP agonism enhances glucose-dependent insulin secretion and is theorized to improve adipose tissue insulin sensitivity, driving Tirzepatide's stronger weight-loss effect. Head-to-head: Tirzepatide 15mg produced ~21% body weight reduction at 72 weeks (SURMOUNT-1) vs Semaglutide 2.4mg's ~15% at 68 weeks (STEP-1). Both use weekly subQ injection with similar titration logic (2.5→15mg for Tirzepatide; 0.25→2.4mg for Semaglutide). Semaglutide has more cardiovascular outcomes data (SELECT trial: 20% major cardiovascular event reduction); Tirzepatide produces larger weight-loss effect. Both have similar GI side-effect profiles driven by GLP-1 activation — nausea peaking during titration and adapting with maintenance.
Compounded Tirzepatide vs Mounjaro vs Zepbound
All three contain the same active peptide — tirzepatide — but differ in regulatory status, presentation, and FDA-approved indication. Mounjaro® is Eli Lilly's FDA-approved pre-filled pen for type 2 diabetes, available at 2.5, 5, 7.5, 10, 12.5, and 15 mg weekly doses. Zepbound® is the identical molecule in a pre-filled pen FDA-approved for chronic weight management, available at the same six dose steps. Compounded Tirzepatide is the same peptide in lyophilized vial form, prepared by licensed 503A compounding pharmacies. Tirzepatide was removed from the FDA's drug shortage list in late 2024, which significantly restricted 503A compounding pathways — users should verify current regulatory status through their pharmacist since the rules have changed since Lilly resolved the shortage. Compounded versions, when available, are chemically equivalent when sourced from reputable pharmacies but lack the pen delivery system and require manual reconstitution and U-100 syringe draws.
Tirzepatide for weight loss — SURMOUNT trial results
The SURMOUNT-1 trial (published 2022, New England Journal of Medicine) tested Tirzepatide at 5mg, 10mg, and 15mg weekly against placebo in 2,539 adults with obesity or overweight plus weight-related comorbidity (non-diabetic). Mean body weight reduction at 72 weeks: 15mg produced ~21% reduction, 10mg produced ~19%, 5mg produced ~15%, placebo produced ~3%. SURMOUNT-2 (obesity + T2D) showed somewhat smaller but still significant effects. SURMOUNT-3 tested the 15mg dose after 12 weeks of intensive lifestyle intervention and showed additional 18.4% weight reduction. SURMOUNT-4 tested weight maintenance after initial loss — continued Tirzepatide maintained weight loss; placebo after Tirzepatide regained most loss within a year. These trials drove FDA approval of Zepbound for chronic weight management in late 2023.
Tirzepatide for type 2 diabetes — SURPASS trial results
The SURPASS program tested Tirzepatide against standard T2D comparators. SURPASS-2 vs Semaglutide 1mg (T2D dose, not obesity dose) showed Tirzepatide produced significantly greater HbA1c reduction and weight loss at every dose. SURPASS-3 vs insulin degludec, SURPASS-4 vs insulin glargine, and SURPASS-5 vs placebo all demonstrated Tirzepatide's superior glycemic control and weight effects. These trials drove FDA approval of Mounjaro in 2022 for type 2 diabetes. For T2D research protocols, dosing mirrors the obesity titration — the molecule and dose range are identical between Mounjaro and Zepbound; the labeling indication is the only difference.
Tirzepatide side effects
Side effects are overwhelmingly gastrointestinal and are the reason the titration schedule exists. Nausea is the most common adverse event, peaks during titration steps (especially 2.5 → 5mg and 10 → 12.5mg), and partially adapts during maintenance. Vomiting and diarrhea occur in a minority and are more frequent at 10mg+ doses. Constipation is common at all dose levels. Decreased appetite is the intended therapeutic effect and is universal. Mild heart rate elevation (~3–5 bpm) is observed. Rare but serious: pancreatitis risk (most relevant for users with pancreatitis history), medullary thyroid carcinoma (boxed warning — contraindicated with MEN2 or personal/family history of MTC), gallbladder disease during rapid weight loss, theoretical increased insulin requirements in T2D patients during titration. Slow titration (full 4-week steps) significantly reduces GI side effects. Users who can't tolerate a step can remain at the previous dose indefinitely — many responders maintain on 5mg or 7.5mg long-term without titrating to max.
Tirzepatide half-life and dosing timing
Tirzepatide has a serum half-life of approximately 5 days (~120 hours) — engineered via a fatty acid chain that binds albumin and slows clearance. This is why Tirzepatide is dosed once weekly rather than daily. Timing within the week is flexible (any day, any time), with or without food. Most users pick a consistent weekly injection day and stick to it. If you miss a dose within 4 days of the scheduled time, inject it as soon as you remember. If it's been >4 days, skip the missed dose and resume the normal weekly schedule — do not double-dose.
How long can you take Tirzepatide?
Unlike research peptides that are conventionally cycled (BPC-157 on/off, Tesamorelin 12-week cycles), Tirzepatide is designed for continuous long-term use. Phase 3 trials run 72 weeks (SURMOUNT-1) or longer. Discontinuation produces substantial weight regain — SURMOUNT-4 showed users who stopped Tirzepatide after initial loss regained most of the lost weight within 12 months, while those who continued maintained their loss. Current clinical guidance treats Tirzepatide as chronic therapy for chronic disease (obesity and T2D are not cured by the drug — the drug manages them). There is no documented tolerance or receptor desensitization at standard doses.