Water volume, concentration and U-100 syringe units for 5, 10, 15, 20, 30 and 60 mg tirzepatide vials, with the label and trial figures as the sources.
Tirzepatide is a dual GIP and GLP-1 receptor agonist. It is approved in the United States as Mounjaro and Zepbound, both supplied as ready solutions, so the approved products are never reconstituted. The lyophilized tirzepatide vial that this page is about is a research-market presentation, sold in sizes that the searches for this page name as 5, 10, 15, 20, 30 and 60 mg, and it has no label. What it has is arithmetic, and the arithmetic is fixed: the milligrams on the vial divided by the millilitres of bacteriostatic water added give the concentration, and the concentration decides how many syringe units any amount occupies.
This page reports that arithmetic for every common vial size, sets the label and trial figures beside it as the only sourced amounts, and points to Medibact's articles for the mixing procedure and for storage. It does not recommend a dose, a water volume or a schedule. The tirzepatide calculator runs the same sums for any vial and any volume; the tirzepatide dosage page reports the figures in more depth; the reconstitution hub indexes every compound.
The arithmetic in one line
Concentration in mg/mL equals vial milligrams divided by water millilitres. Units on a U-100 syringe equal the amount in milligrams divided by the concentration, multiplied by 100, because a U-100 syringe holds 100 units in 1 mL and each small notch on a standard 1 mL insulin syringe is 1 unit (MedlinePlus, "Giving an insulin injection", reviewed 2024-07-21). Nothing about tirzepatide changes those two sentences. Everything below is those two sentences applied.
Water volume per vial size
The three volumes are the ones the calculator pages use throughout this site. Any other volume works the same way.
| Vial |
1 mL of water |
2 mL of water |
3 mL of water |
| 5 mg |
5 mg/mL |
2.5 mg/mL |
1.67 mg/mL |
| 10 mg |
10 mg/mL |
5 mg/mL |
3.33 mg/mL |
| 15 mg |
15 mg/mL |
7.5 mg/mL |
5 mg/mL |
| 20 mg |
20 mg/mL |
10 mg/mL |
6.67 mg/mL |
| 30 mg |
30 mg/mL |
15 mg/mL |
10 mg/mL |
| 60 mg |
60 mg/mL |
30 mg/mL |
20 mg/mL |
Two vials can land on the same concentration: a 10 mg vial in 1 mL and a 30 mg vial in 3 mL are both 10 mg/mL, and every unit figure is then identical. The vial size decides how many amounts the vial holds; the water decides the reading.
Units for the label amounts
The amounts in the table are the ones the Zepbound label names: a starting dosage of 2.5 mg once weekly for four weeks, increases in 2.5 mg increments after at least four weeks, maintenance dosages of 5, 10 or 15 mg, and a maximum of 15 mg once weekly (DailyMed, label ZEP-0016-USPI-20260828, read 2026-09-18). They are listed here as the amounts a reader will meet in the sources, not as a plan.
| Concentration |
2.5 mg |
5 mg |
7.5 mg |
10 mg |
12.5 mg |
15 mg |
| 2.5 mg/mL |
100 units |
200 |
300 |
400 |
500 |
600 |
| 3.33 mg/mL |
75 |
150 |
225 |
300 |
375 |
450 |
| 5 mg/mL |
50 |
100 |
150 |
200 |
250 |
300 |
| 6.67 mg/mL |
37.5 |
75 |
112.5 |
150 |
187.5 |
225 |
| 7.5 mg/mL |
33.3 |
66.7 |
100 |
133.3 |
166.7 |
200 |
| 10 mg/mL |
25 |
50 |
75 |
100 |
125 |
150 |
| 15 mg/mL |
16.7 |
33.3 |
50 |
66.7 |
83.3 |
100 |
| 20 mg/mL |
12.5 |
25 |
37.5 |
50 |
62.5 |
75 |
| 30 mg/mL |
8.3 |
16.7 |
25 |
33.3 |
41.7 |
50 |
A figure above 100 does not fit in one U-100 syringe. A figure with a fraction of a unit falls between the marks of a 1-unit syringe. Both are properties of the concentration, and both move when the water volume moves: a dilute mix gives readable numbers for small amounts and impossible numbers for large ones; a concentrated mix does the reverse.
The 10 mg vial
The most searched version of the question is what volume goes into a 10 mg vial. The answer is that the volume is a choice about readability, not about correctness. At 1 mL the vial is 10 mg/mL: 2.5 mg is 25 units and 10 mg is 100 units, exactly one syringe. At 2 mL it is 5 mg/mL: 2.5 mg is 50 units and 10 mg is 200 units, two full syringes. At 3 mL it is 3.33 mg/mL and 2.5 mg is 75 units. A 10 mg vial holds four 2.5 mg amounts, two 5 mg amounts or one 10 mg amount whatever the volume; the water changes only the volume each one occupies.
The 30 mg vial and the 60 mg vial
Large vials push the arithmetic the other way. A 30 mg vial in 1 mL is 30 mg/mL, and 2.5 mg is 8.3 units, a reading between marks; the same vial in 3 mL is 10 mg/mL and 2.5 mg is a plain 25 units. A 60 mg vial in 3 mL is 20 mg/mL, where 2.5 mg is 12.5 units and 15 mg is 75 units. The largest vials are the ones where the water volume decides whether the small label steps can be read at all.
What the approved product's own numbers show
The approved solution is a useful check on any calculation, because its concentrations are printed on the label. Zepbound single-dose vials contain 2.5, 5, 7.5, 10, 12.5 or 15 mg in 0.5 mL, which is 5, 10, 15, 20, 25 and 30 mg/mL; the multi-dose vials contain 10 to 60 mg in 2.4 mL, which the label states as 4.17 to 25 mg/mL (DailyMed, read 2026-09-18). A 5 mg amount drawn from a research vial mixed to 10 mg/mL is 0.5 mL, the same volume as the approved 5 mg vial. The approved product covers the same concentration band that the tables above cover, which is a useful sanity check on any figure a calculator returns.
Mixing steps, as labels describe them
No tirzepatide label describes mixing, because the approved products arrive dissolved. The steps that approved lyophilized peptide labels describe are consistent from product to product: the diluent is added to the vial, the vial is rolled gently rather than shaken, and the solution is inspected and used only if clear and free of particles (Egrifta SV label, DailyMed, revised 03/2024, read 2026-09-18). The general procedure for any peptide vial, with the supplies and the order of operations, is Medibact's how to reconstitute peptides article; this page does not repeat it.
Storage after mixing
The only labelled statement is for the approved solution: the Zepbound label keeps a single-dose pen or vial at 2 to 8 °C and allows up to 21 days unrefrigerated at up to 30 °C (DailyMed, read 2026-09-18); a mixed research vial has no label, and storage is covered by Medibact's how to store peptides.
The label figures carry a route (subcutaneous), a frequency (once weekly), a titration interval (at least four weeks) and a population (adults meeting the label's indications). SURMOUNT-1, the trial behind the weight-reduction indication, randomised 2,539 adults to 5, 10 or 15 mg weekly or placebo for 72 weeks including a 20-week escalation, and reported mean weight changes of -15.0%, -19.5% and -20.9% against -3.1% (New England Journal of Medicine, 2022-07-21, PMID 35658024). None of that transfers to a research vial by arithmetic: the tables convert milligrams to units and nothing else. Two other facts sit around the vial market. FDA's enforcement discretion for compounded tirzepatide ended for 503A pharmacies in February 2025 and for 503B facilities on 2025-03-19 (National Community Pharmacists Association, 2025-03-13, read 2026-09-18), and the store's tirzepatide vs retatrutide comparison sets the two compounds side by side. The evidence, mechanism and sourcing belong to Medibact's tirzepatide guide.
Sources and dates
Opened 2026-09-18: DailyMed, tirzepatide search (eight records, all Mounjaro or Zepbound solutions) and the Zepbound label (ZEP-0016-USPI-20260828); MedlinePlus, "Giving an insulin injection" (reviewed 2024-07-21); PubMed record 35658024 (SURMOUNT-1); the Egrifta SV label on DailyMed for the mixing description; the National Community Pharmacists Association report of 2025-03-13 on the end of compounding discretion. Vial sizes are the ones the calculator preset and the searches for this page use.
This page does not recommend a dose, a water volume, a syringe or a schedule, and it does not say what any figure means for a particular person. It reports what the sources state and converts milligrams into millilitres and units, which is all that a reconstitution page can honestly do.
