Quick answer
To reconstitute tirzepatide, add a measured volume of bacteriostatic water slowly down the inside wall of the lyophilized vial and swirl gently until clear. Concentration equals milligrams of peptide divided by millilitres of diluent. For a 30 mg vial, 3 mL gives 10 mg/mL and 6 mL gives 5 mg/mL (a 6 mL fill needs a vial large enough to hold it). For a 15 mg vial, 3 mL gives 5 mg/mL; for a 10 mg vial, 2 mL gives 5 mg/mL. Store the solution at 2–8 °C, protected from light, and apply a 28-day in-use limit.
- Diluent: bacteriostatic water (0.9% benzyl alcohol) for multi-use stock; unpreserved sterile water for same-day analytical work
- Technique: no shaking, no vortexing; tirzepatide is lipidated and foams
- Tool: the reconstitution calculator covers any vial size and target
Tirzepatide is supplied to laboratories as a lyophilized powder, most often in larger fills than other research peptides. That makes the reconstitution arithmetic slightly less forgiving: a 30 mg vial dissolved in too little diluent produces a viscous, highly concentrated stock, and too much will not fit in the vial. This guide gives the formula, the volume and concentration tables for every common vial size, syringe-scale conversions, aliquot planning and storage conditions. For laboratory research use only; not for human consumption.
Tirzepatide: research background
Tirzepatide (development code LY3298176) is a 39-amino-acid linear synthetic peptide engineered as a dual agonist of the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. Its sequence is based on native GIP and includes two non-coded aminoisobutyric acid (Aib) residues. A C20 fatty-diacid chain is attached through a hydrophilic linker to the lysine at position 20, which promotes albumin binding in experimental systems.
| Property | Value | Why it matters at the bench |
|---|---|---|
| Length | 39 amino acids | Mid-sized peptide; dissolves readily in aqueous diluent |
| Molecular formula | C225H348N48O68 | Identity confirmation by mass spectrometry |
| Molecular weight | About 4,813.5 g/mol | 1 mg/mL ≈ 208 µM |
| Lipidation | C20 fatty diacid on Lys20 | Amphiphilic; foams and can self-associate if agitated |
| Supplied form | White to off-white lyophilized powder | Requires reconstitution before use |
For the pharmacology literature see the tirzepatide research overview and mechanism of action; for structure, see chemical structure and synthesis.
The reconstitution formula
Everything in this article follows from one relationship and its two rearrangements:
- Concentration (mg/mL) = peptide mass (mg) ÷ diluent volume (mL)
- Diluent volume (mL) = peptide mass (mg) ÷ target concentration (mg/mL)
- Withdrawal volume (mL) = mass required (mg) ÷ concentration (mg/mL)
The lyophilized cake itself adds a negligible volume, so the total solution volume is taken to equal the diluent volume added.
Tirzepatide concentration table: 30 mg vial
| Target concentration | Bacteriostatic water to add | Peptide per 0.1 mL (10 units) | Practical note |
|---|---|---|---|
| 20 mg/mL | 1.5 mL | 2 mg | Concentrated; allow extra time to dissolve |
| 15 mg/mL | 2.0 mL | 1.5 mg | Fits a 3 mL vial |
| 12 mg/mL | 2.5 mL | 1.2 mg | Fits a 3 mL vial |
| 10 mg/mL | 3.0 mL | 1 mg | Simplest math; common default |
| 5 mg/mL | 6.0 mL | 0.5 mg | Needs a 10 mL vial or transfer to a larger sterile container |
| 2 mg/mL | 15.0 mL | 0.2 mg | Prepare as a secondary dilution, not in the original vial |
Tirzepatide concentration table: 15 mg vial
| Target concentration | Bacteriostatic water to add | Peptide per 0.1 mL (10 units) | Practical note |
|---|---|---|---|
| 15 mg/mL | 1.0 mL | 1.5 mg | Concentrated |
| 10 mg/mL | 1.5 mL | 1 mg | Simple math |
| 7.5 mg/mL | 2.0 mL | 0.75 mg | — |
| 5 mg/mL | 3.0 mL | 0.5 mg | Common default |
| 2 mg/mL | 7.5 mL | 0.2 mg | Secondary dilution |
Tirzepatide concentration table: 5 mg and 10 mg vials
| Vial size | Bacteriostatic water to add | Concentration | Peptide per 0.1 mL (10 units) |
|---|---|---|---|
| 5 mg | 1.0 mL | 5 mg/mL | 0.5 mg |
| 5 mg | 2.0 mL | 2.5 mg/mL | 0.25 mg |
| 10 mg | 1.0 mL | 10 mg/mL | 1 mg |
| 10 mg | 2.0 mL | 5 mg/mL | 0.5 mg |
| 10 mg | 2.5 mL | 4 mg/mL | 0.4 mg |
Syringe-scale conversion (U-100, 1 mL = 100 units)
When volumes are measured with a 1 mL laboratory syringe marked in units, each unit is 0.01 mL. This table shows the reading that corresponds to a given peptide mass at the two most common stock concentrations.
| Peptide mass per aliquot | At 10 mg/mL | At 5 mg/mL |
|---|---|---|
| 0.5 mg | 0.05 mL = 5 units | 0.10 mL = 10 units |
| 1 mg | 0.10 mL = 10 units | 0.20 mL = 20 units |
| 2.5 mg | 0.25 mL = 25 units | 0.50 mL = 50 units |
| 5 mg | 0.50 mL = 50 units | 1.00 mL = 100 units |
| 7.5 mg | 0.75 mL = 75 units | 1.50 mL (two withdrawals) |
Worked example. A 30 mg vial is reconstituted with 3 mL: 30 ÷ 3 = 10 mg/mL. A stability study needs 2.5 mg per time point. Volume = 2.5 ÷ 10 = 0.25 mL (25 units). The vial yields 3 ÷ 0.25 = 12 time points. In molar terms the stock is roughly 2.08 mM.
Adjusting for actual COA fill weight
The number on the label is a nominal fill. Two figures on the certificate of analysis refine it:
- Net peptide content per vial, when reported, is the actual mass. A "30 mg" vial may be documented at 30.8 mg or 29.5 mg.
- HPLC purity is the fraction of peptide-related material that is the target compound.
For routine work the nominal value is adequate. For quantitative assays, use: corrected concentration = (measured content in mg × purity as a decimal) ÷ diluent volume. Example: 30.8 mg at 99.1% purity in 3 mL gives (30.8 × 0.991) ÷ 3 = 10.17 mg/mL rather than a nominal 10.00. How those numbers are generated is explained in tirzepatide purity testing and how to read a COA.
Diluent selection
| Diluent | Use it when | Avoid it when |
|---|---|---|
| Bacteriostatic water (0.9% benzyl alcohol) | The vial will be entered repeatedly over days to weeks | Cell culture; assays sensitive to benzyl alcohol |
| Sterile water, unpreserved | Single-session analytical work; HPLC or MS sample preparation | Any multi-use stock |
| Phosphate-buffered saline, sterile | Cell-based or receptor assays needing physiological pH and tonicity | Long storage; highly concentrated stocks |
The commercially formulated liquid product is a phosphate-buffered solution with sodium chloride, which shows that tirzepatide tolerates near-neutral buffered conditions. Lyophilized research material is a different presentation, however, and may contain different counter-ions or bulking agents, so do not assume identical behavior. More on the diluent itself is in bacteriostatic water for peptides.
Step-by-step handling protocol
- Equilibrate the tirzepatide vial and the diluent at room temperature for 15–20 minutes.
- Prepare a clean surface or laminar-flow hood; put on gloves.
- Swab both stoppers with 70% isopropyl alcohol and allow them to dry.
- Calculate the diluent volume from the tables above and write the target concentration down.
- Draw the diluent with a sterile syringe, clearing bubbles.
- Add the diluent slowly with the needle tip against the glass so liquid runs down the wall. With a 30 mg fill, consider adding it in two portions, swirling between them.
- Swirl gently. Larger fills at 10 mg/mL or above can take three to five minutes. Never shake or vortex.
- Inspect against light and dark backgrounds: clear, colorless, particle-free.
- Label with compound, lot, mg/mL, diluent, date and initials, then refrigerate.
The general technique is described in more depth in how to reconstitute a lyophilized peptide.
Aliquot volume reference
Dividing a stock into single-use aliquots limits repeated vial entry and removes freeze–thaw cycling from the equation. The counts below ignore dead volume; in practice expect to lose 5–10% to pipette tips and tube walls.
| Vial size | Concentration | Total volume | 50 µL aliquots | 100 µL aliquots | 250 µL aliquots | 500 µL aliquots |
|---|---|---|---|---|---|---|
| 10 mg | 5 mg/mL | 2.0 mL | 40 | 20 | 8 | 4 |
| 15 mg | 5 mg/mL | 3.0 mL | 60 | 30 | 12 | 6 |
| 15 mg | 10 mg/mL | 1.5 mL | 30 | 15 | 6 | 3 |
| 30 mg | 10 mg/mL | 3.0 mL | 60 | 30 | 12 | 6 |
| 30 mg | 5 mg/mL | 6.0 mL | 120 | 60 | 24 | 12 |
Use low-protein-binding polypropylene tubes. Lipidated peptides adsorb to glass and standard plastics at low concentrations, and the loss is proportionally greatest in small, dilute aliquots.
Storage conditions
| Form | Recommended storage | Working time frame | Notes |
|---|---|---|---|
| Lyophilized, sealed | −20 °C, dry, dark | Long term; follow COA retest date | Equilibrate before opening to avoid condensation |
| Lyophilized, sealed | 2–8 °C | Short term (weeks) | Suitable between delivery and use |
| Reconstituted in bacteriostatic water | 2–8 °C, protected from light | Up to 28 days | Multi-use container convention; shorter for quantitative work |
| Reconstituted in unpreserved diluent | 2–8 °C | Same day | Single use |
| Single-use frozen aliquots | −20 °C or below | Per lab SOP | Thaw once; never refreeze |
| On the bench during handling | 20–25 °C | Keep as brief as practical | Return to cold storage promptly |
See tirzepatide storage and stability for degradation pathways and how research peptides are shipped for transit conditions.
Troubleshooting
| Observation | Probable cause | Response |
|---|---|---|
| Persistent foam | Diluent added too fast or vial agitated | Stand upright 10–15 minutes; foam collapses |
| Gel-like clumps | Stream aimed at cake; local over-concentration | Allow more time; swirl gently; do not heat |
| Haze that does not clear | Concentration too high, aggregation or contamination | Do not use; document lot and contact supplier |
| Diluent will not fit | Target concentration too dilute for the vial | Reconstitute concentrated, then dilute in a larger sterile container |
| Results drift low over weeks | Adsorption or slow degradation in solution | Use low-bind tubes; prepare fresh stock more often |
Handling checklist
- One vial, one record. Log the peptide lot, diluent lot, volume added, resulting mg/mL and date in the lab notebook at the time of reconstitution, not afterwards.
- Fresh needle for every entry. Swab the stopper each time and vary the puncture point to limit coring.
- Minimize headspace exchange. Withdraw only what the session requires; do not pump air in and out of the vial.
- Keep it cold and dark. Store upright on a middle shelf at 2–8 °C, not in the door and not against the back wall where freezing can occur.
- Do not pool vials. Combining the remnants of two lots creates a stock with no single COA behind it.
- Discard on schedule. At 28 days, or sooner if the solution turns hazy, the vial is finished.
Sourcing tirzepatide for research
Reconstitution math is only as good as the material in the vial. Look for batch-specific HPLC purity, mass-spectrometry identity confirmation and a lot number that matches the documentation. V8 Peptides supplies tirzepatide in 30 mg vials with a published certificate of analysis for each lot. Comparative reading: retatrutide vs tirzepatide and semaglutide vs tirzepatide.
References
- Coskun T, Sloop KW, Loghin C, et al. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: from discovery to clinical proof of concept. Mol Metab. 2018;18:3–14.
- Eli Lilly and Company. Mounjaro (tirzepatide) prescribing information: description and storage sections. DailyMed, U.S. National Library of Medicine.
- United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding—Sterile Preparations. USP–NF.
- United States Pharmacopeia. General Chapter <51> Antimicrobial Effectiveness Testing. USP–NF.
- Hospira, Inc. (Pfizer). Bacteriostatic Water for Injection, USP — package insert. DailyMed, U.S. National Library of Medicine.
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575.
- Carpenter JF, Pikal MJ, Chang BS, Randolph TW. Rational design of stable lyophilized protein formulations: some practical advice. Pharm Res. 1997;14(8):969–975.
Frequently asked questions
How much bacteriostatic water do I add to a 30 mg tirzepatide vial?
3 mL gives 10 mg/mL, the most convenient concentration for a 30 mg fill. 2 mL gives 15 mg/mL and 6 mL gives 5 mg/mL, though 6 mL requires a vial with enough capacity.
How much bacteriostatic water for a 15 mg tirzepatide vial at 5 mg/mL?
3 mL. The calculation is 15 mg ÷ 5 mg/mL = 3 mL.
How much bacteriostatic water for a 10 mg tirzepatide vial?
2 mL gives 5 mg/mL and 1 mL gives 10 mg/mL. At 5 mg/mL, each 0.1 mL (10 units on a U-100 laboratory syringe) contains 0.5 mg.
Does tirzepatide dissolve easily in bacteriostatic water?
Yes. It normally dissolves to a clear solution within a few minutes of gentle swirling. Large fills at high concentration take longer, and foaming is common if the diluent is added quickly.
Can I shake the vial to speed things up?
No. Tirzepatide is a lipidated peptide and agitation generates foam and promotes aggregation at the air–liquid interface. Slow swirling and patience give a better result.
How long is reconstituted tirzepatide stable?
In bacteriostatic water at 2–8 °C and protected from light, laboratories typically apply a 28-day in-use limit based on the multi-use container convention. For quantitative work, prepare fresh stock more frequently or use frozen single-use aliquots.
Can I freeze reconstituted tirzepatide?
Only as single-use aliquots that are thawed once. Repeated freeze–thaw cycles encourage aggregation and concentration drift.
How do I convert mg/mL to units on a lab syringe?
On a U-100 scale, 100 units equal 1 mL. Divide the mass you need by the concentration to get millilitres, then multiply by 100. At 10 mg/mL, 2.5 mg is 0.25 mL, or 25 units.
What is the molar concentration of a 10 mg/mL tirzepatide stock?
Using a molecular weight of about 4,813.5 g/mol, 10 mg/mL is approximately 2.08 mM, and 1 mg/mL is approximately 208 µM.
How does vial size affect how much bacteriostatic water I need to keep on hand?
A 30 mg vial at 10 mg/mL uses 3 mL, so one 10 mL bottle of bacteriostatic water reconstitutes three such vials inside its 28-day in-use window. Smaller peptide fills use proportionally less.
How does tirzepatide differ from retatrutide in handling?
Very little. Both are 39-residue lipidated peptides that dissolve in bacteriostatic water and foam if agitated. Retatrutide additionally targets the glucagon receptor; the bench protocol is the same. See how to reconstitute retatrutide.