Guide

Zepbound & Mounjaro: Vial vs KwikPen vs Pen

Zepbound® and Mounjaro® (tirzepatide) come in four presentations: single-dose pens, single-dose vials, multi-dose vials and KwikPens. They hold different numbers of doses and are measured differently, so the same 10 mg dose is 0.5 mL in one and 0.6 mL in another. Here is how to tell them apart, read the label, and know when a calculator helps.

Checked against both FDA labels and their Instructions for Use on October 19, 2026.

The Instructions for Use that come with your presentation always take priority. Your healthcare provider should tell you which one you will receive and train you on it, and if your presentation changes, read its new instructions before your next dose.

At a glance

The four presentations

Zepbound and Mounjaro come in the same four presentations and strengths; only the single-dose vial carton sizes differ.

Single-dose pen

1 dose in 0.5 mL

Strengths: 2.5 to 15 mg per 0.5 mL
Comes as: Carton of 4 pens
How the dose is given: Place the clear base on your skin, unlock it, then press and hold the purple button for up to 10 seconds. The second click means the injection is complete.
After use: Used once. Put the whole pen in a sharps container.
Storage: Refrigerate at 2–8 °C (36–46 °F). If needed, it can be kept unrefrigerated, not above 30 °C (86 °F), for up to 21 days in total.

No calculator

Nothing to measure: the pen gives its whole dose.

Single-dose vial

1 dose in 0.5 mL

Strengths: 2.5 to 15 mg per 0.5 mL
Comes as: Carton of 1 vial (Zepbound also comes in cartons of 4)
How the dose is given: Draw to the 0.5 mL line with a new syringe and needle (not included).
After use: Throw the vial away after use, even if medicine is left in it.
Storage: Refrigerate at 2–8 °C (36–46 °F). If needed, it can be kept unrefrigerated, not above 30 °C (86 °F), for up to 21 days in total.

Nothing to calculate

Nothing to calculate: the dose is the whole 0.5 mL.

Multi-dose vial

4 weekly doses in 2.4 mL

Strengths: 10 to 60 mg per 2.4 mL (2.5 to 15 mg per 0.6 mL dose)
Comes as: Carton of 1 vial
How the dose is given: Each week, draw to the 0.6 mL line with a new syringe and needle (not included), for example a 1 mL syringe your healthcare provider recommends.
After use: Throw it away after 4 weekly doses, 30 days after first use, or 30 days in total at room temperature, whichever comes first, even if medicine is left. A missed or late dose doesn’t extend the 30 days.
Storage: Unopened: refrigerate at 2–8 °C until the expiration date, or up to 30 days at room temperature (not above 30 °C). Opened: keep it in its carton, in the fridge or at room temperature up to 30 °C.

Cross-check only

The label already gives the volume, 0.6 mL. A calculator can only double-check it.

KwikPen

4 fixed weekly doses in 2.4 mL

Strengths: 10 to 60 mg per 2.4 mL (2.5 to 15 mg per dose)
Comes as: Carton of 1 single-patient-use pen
How the dose is given: Attach a new KwikPen-compatible pen needle (not included), prime the pen before every injection, then turn the dose knob all the way until it stops.
After use: Throw it away after 4 weekly doses, 30 days after first use, or 30 days in total at room temperature, whichever comes first, even if medicine is left. A missed or late dose doesn’t extend the 30 days. Don’t inject the leftover medicine.
Storage: Unopened: refrigerate at 2–8 °C until the expiration date, or up to 30 days at room temperature (not above 30 °C). Opened: keep it in its carton, in the fridge or at room temperature up to 30 °C.

No calculator

Never draw medicine from a KwikPen into a syringe.

Identify yours

How to tell which one you have

01
Read the name on the label
Look for single-dose pen, single-dose vial, multi-dose vial or KwikPen. Single-dose pens and vials hold one dose; multi-dose vials and KwikPens hold four weekly doses.
02
Check how the strength is written
Single-dose pens and vials print one dose per 0.5 mL, such as “10 mg/0.5 mL”. Multi-dose vials and KwikPens print the whole contents per 2.4 mL plus a strength per mL, such as “40 mg/2.4 mL (16.7 mg/mL)”.
03
Look at the device
A single-dose pen has a gray base cap, a clear base, a lock ring and a purple injection button. A KwikPen has a dose knob and a dose window and needs a separate pen needle. A vial has a rubber stopper and needs a separate syringe and needle.
04
Still unsure? Ask before you inject
Your pharmacist can confirm which presentation you were given. Don’t guess from a previous prescription: a new fill can be a different presentation.

Same dose, different volume

A 10 mg/0.5 mL single-dose vial and a 40 mg/2.4 mL multi-dose vial both give a 10 mg dose, but one is the whole 0.5 mL and the other is 0.6 mL. Never use one presentation’s volume for another.

Read the label

The three numbers on a multi-dose label

Dose per injection: 10 mg/0.6 mL; What one weekly injection contains, and its volume. This is the number that matches your prescription.
Total strength per total volume: 40 mg/2.4 mL; Everything in the vial or KwikPen: four doses. These two numbers are exact.
Strength per mL: 16.7 mg/mL; The concentration, printed rounded. 40 ÷ 2.4 is really 16.666…, so dividing by 16.7 is slightly off.

Syringe units are for multi-dose vials only. Never use them with a KwikPen: don’t draw its medicine into a syringe or try to change its dose. Prime it and turn the dose knob until it stops, as its Instructions for Use say.

Multi-dose vials and KwikPens of Zepbound and Mounjaro share these strengths: 2.4 mL, 4 doses of 0.6 mL. Vial units are on a U-100 syringe (100 units = 1 mL), calculated by DoseMarks.

Multi-dose vial and KwikPen strengths. Syringe units apply to vials only, never to a KwikPen.
Dose per injection	Vial only: syringe draw	Total strength	Printed mg/mL	Calculated mg/mL (approx.)
2.5 mg/0.6 mL	0.6 mL = 60 units	10 mg/2.4 mL	4.17 mg/mL	≈ 4.167 mg/mL
5 mg/0.6 mL	0.6 mL = 60 units	20 mg/2.4 mL	8.33 mg/mL	≈ 8.333 mg/mL
7.5 mg/0.6 mL	0.6 mL = 60 units	30 mg/2.4 mL	12.5 mg/mL	12.5 mg/mL
10 mg/0.6 mL	0.6 mL = 60 units	40 mg/2.4 mL	16.7 mg/mL	≈ 16.667 mg/mL
12.5 mg/0.6 mL	0.6 mL = 60 units	50 mg/2.4 mL	20.8 mg/mL	≈ 20.833 mg/mL
15 mg/0.6 mL	0.6 mL = 60 units	60 mg/2.4 mL	25 mg/mL	25 mg/mL

Using a calculator

Which numbers belong in a calculator

Multi-dose vial: cross-check the 0.6 mL

Example: a 10 mg dose from a 40 mg/2.4 mL (16.7 mg/mL) vial. Either way of entering it should give the label’s answer.

Label concentration: 16.7 mg/mL, 2.4 mL in the vial, dose 10 mg → 0.6 mL (60 units), 4 doses per vial. DoseMarks recognizes 16.7 as a rounded number.
Amount + volume: 40 mg in 2.4 mL, dose 10 mg → exactly 0.6 mL (60 units), 4 doses.

If a calculator gives anything other than 0.6 mL, stop and check what you entered — the label is right.

Open the tirzepatide calculator

Single-dose vial: nothing to calculate

The dose is the whole 0.5 mL. Draw to the 0.5 mL line, and throw the vial away afterwards even if medicine is left.

Single-dose pen and KwikPen: never

Pens set their own dose. Don’t transfer medicine from a pen into a syringe. Throw a KwikPen away after 4 weekly doses, 30 days after first use, or 30 days in total at room temperature, whichever comes first, and don’t inject what is left in it.

What a calculator can’t tell you

Your dose. Each multi-dose vial is labeled for four doses of one strength; the label doesn’t describe taking a different dose from it. If your dose changes, ask your prescriber which presentation to use.
Which syringe and needle to use. They aren’t included with vials; your healthcare provider recommends them.
Whether a compounded product matches a branded one. It doesn’t: use the strength and volume on the pharmacy label.

Instructions for Use

Always follow your presentation’s instructions for

Injection technique, including how to draw from a vial and remove air bubbles.
Priming a KwikPen before every injection and turning the dose knob all the way.
Using a new syringe and needle, or a new pen needle, for every injection.
Checking the medicine first: clear, colorless to slightly yellow, no particles, never frozen.
Storage, and when to throw a vial or pen away (it differs by presentation, see above).
Injection sites, rotating them, and safe sharps disposal. Never share pens, needles or syringes.

Good to know

Vials, pens and KwikPens: FAQ

Is the Zepbound KwikPen the same as the Zepbound pen?

No. The single-dose pen holds one 0.5 mL dose and is used once. The KwikPen holds four fixed weekly doses in 2.4 mL: you attach a new pen needle, prime it before every injection and turn the dose knob all the way until it stops. Like a multi-dose vial, it is thrown away after 4 weekly doses, 30 days after first use, or 30 days in total at room temperature, whichever comes first.

How many units is 0.6 mL on an insulin syringe?

On a U-100 syringe 100 units = 1 mL, so 0.6 mL is the 60-unit mark and 0.5 mL is the 50-unit mark. The Zepbound and Mounjaro instructions measure vial doses in mL; use the syringe your healthcare provider recommends.

Why doesn’t 10 mg ÷ 16.7 mg/mL come out to exactly 0.6 mL?

Because 16.7 is rounded. A 40 mg / 2.4 mL vial is 16.666… mg/mL, and 10 mg of it is exactly 0.6 mL. Dividing by the rounded number gives 0.599 mL (59.9 units). DoseMarks treats a printed value like 16.7 as rounded, or you can enter 40 mg in 2.4 mL for an exact answer.

Can I draw medicine out of a KwikPen with a syringe?

No. The KwikPen Instructions for Use say not to transfer the medicine from the pen into a syringe, and not to inject leftover medicine, because it may not be a full dose. If the dose knob won’t turn all the way, throw the pen away.

How long can I use an opened multi-dose vial or KwikPen?

The same limits apply to both. Throw it away after 4 weekly doses, 30 days after first use, or 30 days in total at room temperature, whichever comes first, even if medicine is left. A missed or late dose doesn’t extend the 30 days. Keep it in its carton, in the fridge or at room temperature up to 30 °C (86 °F).

Is a branded multi-dose vial the same as a compounded tirzepatide vial?

No. A branded multi-dose vial contains FDA-approved Zepbound or Mounjaro at a labeled strength, with four 0.6 mL doses. Compounded vials are not FDA-approved; their strength and volume are whatever the pharmacy label says, and FDA recommends discarding them within 28 days of first use.

Sources

References

Zepbound®, Mounjaro® and KwikPen® are registered trademarks of Eli Lilly and Company. DoseMarks is independent and is not affiliated with or endorsed by Lilly. This guide is educational and does not replace the prescribing information, the Instructions for Use or your healthcare provider. Last updated October 2026.