Guides / Mixing and syringes

How to draw a dose from a vial with an insulin syringe

The Zepbound and Mounjaro vial instructions, MedlinePlus and the CDC all describe the same short routine. The two habits that matter most are a new needle every time and checking for air.

By PeptideTracker editorial team · Updated November 8, 2026 · 7 sources

[00] Short answer

  1. Wipe the rubber stopper with an alcohol swab and let it dry. Then pull air into the syringe equal to your dose and push it into the vial1,3.
  2. Turn the vial upside down, keep the needle tip in the liquid, and draw slowly past your line. Tap any bubbles to the top and push back up to the line1.
  3. A Zepbound or Mounjaro single-dose vial dose is 0.5 mL (50 units on a U-100 syringe). A multi-dose vial dose is 0.6 mL (60 units)1.
  4. Use a new needle and syringe every time you go into a vial, even for your own second dose1,5.
  5. After injecting, keep the needle in your skin for at least 5 seconds, then put it straight in a sharps container without recapping1,3.

How do you draw from a vial with an insulin syringe?

Clean the stopper, put in air equal to your dose, turn the vial over, draw a little past your line, clear the bubbles and push back to the line. The steps below follow the US Zepbound vial Instructions for Use, which match the Mounjaro vial instructions word for word1–2. Where MedlinePlus, the syringe maker or the CDC add something, it's marked.

  1. Wash your hands and check the vial
    Wash with soap and water. Check the label is the right medicine and strength and that it hasn't expired. Zepbound and Mounjaro should not be frozen or cloudy, should be colorless to slightly yellow, and should have no particles1–2.
  2. Take off the plastic cap, not the stopper
    On a new vial, pull off the plastic protective cap. Leave the rubber stopper in place1.
  3. Wipe the stopper and let it dry
    Wipe the rubber stopper with an alcohol swab1. MedlinePlus adds: let it dry, and don't blow on it3. The CDC says to do this every time, before each puncture5–6.
  4. Use a new syringe and needle
    Unwrap a new syringe (and attach the needle if it isn't built in), then pull the needle shield straight off1. The label says to use a new syringe and needle for each injection, to prevent infections and blocked needles1.
  5. Pull in air equal to your dose
    Hold the syringe needle up and pull the plunger down to your dose line: 0.5 mL for a single-dose Zepbound vial, 0.6 mL for a multi-dose vial1. For a mixed peptide vial, that's the number of units the calculator gives you.
  6. Push the air into the vial
    Push the needle through the rubber stopper and press the plunger all the way in. The air makes it easier to pull the liquid out1. The syringe maker's guide says to go through the center of the stopper, straight in at 90 degrees4.
  7. Turn it over and draw past your line
    Turn the vial and syringe upside down. Make sure the needle tip is in the liquid, then pull the plunger slowly until its tip is past your line1.
  8. Tap out the bubbles and push back to the line
    If you see bubbles, tap the syringe gently a few times so they rise to the top. Then push the plunger slowly up until its tip sits on your line1. That pushes the air and the extra liquid back into the vial3–4.
  9. Take the needle out of the vial
    Pull the syringe straight out of the stopper1. Don't leave a needle sitting in the stopper for later. The CDC says that gives germs a direct route into the vial7.
  10. Inject, then hold for 5 seconds
    Insert the needle, push the plunger down, and keep the needle in your skin for at least 5 seconds so the whole dose goes in1. Don't recap it. Put the needle and syringe in a sharps container right away1.

Where to inject and how to move between spots each week is in our injection sites guide.

How much do you draw from a Zepbound or Mounjaro vial?

Draw 0.5 mL from a Zepbound or Mounjaro single-dose vial and 0.6 mL from a multi-dose vial, whatever the strength1–2. On a U-100 insulin syringe, where 100 units fill 1 mL, that's the 50 and 60 unit lines. The strength printed on the vial (2.5 mg, 5 mg and so on) changes how much medicine is in the liquid, not how much liquid you draw.

Volume to draw per dose, and the matching U-100 syringe line
VialDrawU-100 syringe lineThrow away
Zepbound or Mounjaro single-dose vial0.5 mL50 unitsRight after the one dose, even if liquid is left1–2
Zepbound or Mounjaro multi-dose vial (4 doses)0.6 mL60 unitsAfter 4 doses, 30 days after first use, or 30 days at room temperature, whichever comes first1–2
Mixed peptide vial (example: 5 mg + 2 mL water, 250 mcg)0.1 mL10 unitsNo label. See the 28-day rule

The peptide row is a worked example of the math, not a dose. For your own vial, use the reconstitution calculator.

The Zepbound vial instructions give a 1 mL syringe as an example and say to use the syringe and needle your healthcare provider recommends. Neither comes in the box1. If you're unsure what the lines on yours mean, see how to read an insulin syringe and U-100 vs U-40 syringes.

[Tool]Work out your units to drawVial mg, water mL and dose in, units out

Why draw past the line and push back?

Drawing a little extra gives you room to push out air and still finish exactly on your line. Air takes up space on the scale, so a bubble means less medicine than the number you read. The Zepbound instructions build this in: draw past the line, tap the bubbles up, then push back to the line1.

If bubbles stay put, MedlinePlus says to hold the vial and syringe in one hand, tap with the other, push the bubbles back into the vial, then pull back to your dose3. The syringe maker gives the same fix: push the liquid back into the vial and draw again4.

Can you reuse a syringe or needle on the same vial?

No. Every source here says one needle and one syringe, used once. The CDC's injection safety checklist says vials should be entered with a new needle and a new syringe, even when getting more doses for the same person5. The Zepbound label says not to reuse or share syringes or needles1, and MedlinePlus says never to reuse them3.

  • Single-dose vials are for one dose only. Throw the vial away after use, even if medicine is left1. The CDC says not to save or pool leftovers7.
  • Multi-dose vials are for one person. The Zepbound and Mounjaro multi-dose vial gives 4 weekly doses within 30 days1–2.
  • Pens are not vials. The Zepbound KwikPen instructions say not to move medicine from the pen into a syringe1.

Used needles go straight into a sharps container. Our sharps disposal guide covers what to use and where it goes when full.

Questions

Do I have to put air into the vial before drawing?

The Zepbound and Mounjaro vial instructions include it. You pull in air equal to your dose and push it into the vial, which makes the liquid easier to draw out.

Why do I draw past the line and then push back?

So you can push out any air bubbles and still finish exactly on your line. The Zepbound instructions say to draw past the line, tap the bubbles up, then push slowly back to the line.

How many units is 0.5 mL on an insulin syringe?

50 units on a U-100 syringe, because 100 units fill 1 mL. That's the dose from a Zepbound or Mounjaro single-dose vial. A multi-dose vial dose is 0.6 mL, the 60-unit line.

Can I use the same needle for a second dose from my own vial?

No. The CDC says to enter a vial with a new needle and a new syringe every time, even for the same person, and the Zepbound label says to use a new syringe and needle for each injection.

Is there extra liquid left in a single-dose vial?

There can be. The Zepbound label says to throw away an opened single-dose vial after use even if there's medicine left, and the CDC says not to keep leftovers from single-dose vials.

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

The pen instructions say no. The Zepbound KwikPen instructions say not to transfer medicine from the pen into a syringe, and not to inject the liquid left after the 4th dose.

Sources

Checked against the Zepbound and Mounjaro single-dose and multi-dose vial Instructions for Use (US, 2026), MedlinePlus, the embecta (BD) insulin syringe injection guide, and CDC injection safety guidance. How we check

  1. 1Zepbound (tirzepatide) injection: US prescribing information and Instructions for Use, single-dose vial, multi-dose vial and KwikPen (DailyMed). Eli Lilly, label revised 08/2026; vial IFU revised April 2026 and January 2026
  2. 2Mounjaro (tirzepatide) injection: US prescribing information and Instructions for Use (DailyMed). Eli Lilly, revised 08/2026; vial Instructions for Use
  3. 3MedlinePlus (US National Library of Medicine), Giving an insulin injection. reviewed 21 Jul 2024
  4. 4embecta (formerly part of BD), BD SafetyGlide insulin syringe with 6mm needle: step-by-step injection guide. steps 3 to 6
  5. 5CDC, Injection Safety Checklist (One & Only Campaign). accessed 8 Nov 2026
  6. 6CDC Project Firstline, How do I safely use a multi-dose vaccine vial? (job aid). accessed 8 Nov 2026
  7. 7CDC, Preventing Unsafe Injection Practices. page dated 26 Mar 2024; accessed 8 Nov 2026

This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.

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