How the Zepbound single-dose and multi-dose vials are drawn per the label: 0.5 or 0.6 mL, the syringe it names, the air step, and what a misread line costs.
Zepbound vials put the reader back in charge of a measurement the pens make for them. The label describes the drawing step in detail, names the syringe only by example, and states every dose as a volume. This page reads those instructions for both vials, converts the volumes into the syringe units this site uses for research vials, and works out what a misread line means in milligrams at each strength.
The ladder the vial strengths belong to is on the label's weekly escalation chart. Medibact's Tirzepatide guide covers the molecule. How the dialled pen does the same job is on the Zepbound KwikPen page.
The two vials
From the label's dosage forms and How Supplied tables (openFDA version 40, effective 2026-08-28):
| Strength |
Single-dose vial |
Concentration |
Multi-dose vial (4 doses) |
Concentration |
| 2.5 mg |
2.5 mg / 0.5 mL |
5 mg/mL |
10 mg / 2.4 mL, 0.6 mL a dose |
4.17 mg/mL |
| 5 mg |
5 mg / 0.5 mL |
10 mg/mL |
20 mg / 2.4 mL |
8.33 mg/mL |
| 7.5 mg |
7.5 mg / 0.5 mL |
15 mg/mL |
30 mg / 2.4 mL |
12.5 mg/mL |
| 10 mg |
10 mg / 0.5 mL |
20 mg/mL |
40 mg / 2.4 mL |
16.7 mg/mL |
| 12.5 mg |
12.5 mg / 0.5 mL |
25 mg/mL |
50 mg / 2.4 mL |
20.8 mg/mL |
| 15 mg |
15 mg / 0.5 mL |
30 mg/mL |
60 mg / 2.4 mL |
25 mg/mL |
The same strength is a different concentration in the two vials. A unit count taken from one cannot be read against the other: 50 units from the 5 mg single-dose vial is 5 mg, while 50 units from the 5 mg multi-dose vial is 4.17 mg. The label avoids the problem by never using units — every dose is the whole 0.5 mL or 0.6 mL.
The syringe the label names
Section 2.4 of the label describes "a syringe appropriate for dose administration (e.g., a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose)" and "a new syringe and needle for each injection". The instructions repeat that the syringe and needle are "supplied separately", recommended by the healthcare provider, and "may look different" from the drawing. The cartons say "Needles and Syringes are not included". The label names no brand, gauge or needle length, and this page does not either; supplies are the store's subject.
Read on a U-100 insulin syringe, 0.5 mL is the 50-unit mark and 0.6 mL the 60-unit mark. How those scales are marked, and why a 1 mL barrel is usually marked in 2-unit steps, is on the insulin syringe units page.
The drawing steps, as the instructions give them
The single-dose and multi-dose instructions follow the same order; only the volume differs.
- Air first. With the needle pointing up, the plunger is pulled down "until the plunger tip reaches the line on the syringe indicating that 0.5 mL of air has been drawn" (0.6 mL for the multi-dose vial). The air goes into the vial, which the instructions say "makes it easier to pull the solution from the vial".
- Upside down, past the line. With vial and syringe inverted and the needle tip in the liquid, the plunger is pulled "until the plunger tip is past the 0.5 mL line" (0.6 mL).
- Bubbles, then back to the line. The syringe is tapped so bubbles rise, and the plunger is pushed up "until the plunger tip reaches the 0.5 mL line". Overdrawing and pushing back is how the instructions make the line the last thing read.
- The injection. After the needle goes in and the plunger is pushed down, "the needle should stay in your skin for at least 5 seconds to make sure you have injected all of your dose."
- Afterwards. A single-dose vial is discarded even if medicine is left in it. A multi-dose vial is discarded after four weekly doses, 30 days after first use or 30 days at room temperature, "even if there is medicine left in it".
The label's injection sites and the timing rules shared with the pens are on where to inject tirzepatide, and why four doses from a vial rarely means a clean remainder is on doses per vial.
What a misread line costs, strength by strength
Because every Zepbound strength sits in the same volume, the same reading error is a different amount of drug on each vial. The table takes an error of 0.05 mL, five units on a U-100 scale or two and a half of the 2-unit marks on a 1 mL barrel:
| Strength |
Single-dose vial: mg in 0.05 mL |
Share of the dose |
Multi-dose vial: mg in 0.05 mL |
Share of the dose |
| 2.5 mg |
0.25 mg |
10% |
0.21 mg |
8.3% |
| 5 mg |
0.5 mg |
10% |
0.42 mg |
8.3% |
| 7.5 mg |
0.75 mg |
10% |
0.63 mg |
8.3% |
| 10 mg |
1.0 mg |
10% |
0.83 mg |
8.3% |
| 12.5 mg |
1.25 mg |
10% |
1.04 mg |
8.3% |
| 15 mg |
1.5 mg |
10% |
1.25 mg |
8.3% |
All figures are arithmetic by this site from the label's concentrations. The share of the dose is constant within a vial type — 0.05 of 0.5 mL is 10%, of 0.6 mL 8.3% — but the milligrams rise sixfold from the lowest strength to the highest. The label does not discuss reading error; the overdraw-and-return step is its only guard against it.
Vial versus pen, in one line each
The single-dose pen delivers a fixed 0.5 mL with no reading at all. The KwikPen delivers 0.6 mL dialled to a stop. The vials are the only Zepbound presentations where the dose depends on a line read by eye, which is why the label asks for training specific to the presentation and retraining when it changes. The unit counts used with compounded and research vials, and why they differ from these, are on tirzepatide in units.
What this page does not establish
It reports the Zepbound label and its vial instructions as read on 2026-10-14 and adds arithmetic. It does not say which vial, strength or syringe anyone should use, and it does not cover needles, storage or cost, which belong to a prescriber, the label and the store's pages.
Sources and dates
Opened 2026-10-14: the ZEPBOUND (tirzepatide) prescribing information, carton text and Instructions for Use for the single-dose and multi-dose vials via the openFDA drug label API (Eli Lilly, set 487cd7e7-434c-4925-99fa-aa80b1cc776b, version 40, effective 2026-08-28) — sections 2.4, 3, 16.1 and 16.2. Unit and milligram figures are arithmetic by this site. Corrections go to the contact page.
