Short answer: Wipe the rubber top with alcohol, pull air into a new syringe equal to your dose, push that air into the vial, turn the vial upside down and draw the dose, then tap out bubbles. CDC says to enter a vial only with a new needle and syringe, never to leave a needle in the stopper, and to date a multi-dose vial when it is opened and throw it away within 28 days unless the maker gives another date.
Before you start
MedlinePlus says to wash your hands and check the vial: the right medicine, the expiry date, and the liquid itself. Look for a change in color, cloudiness or bits floating in it. If you will use the vial more than once, write the date you open it on the label.
A multi-dose vial holds more than one dose and is made to be entered more than once. Testosterone cypionate in 10 mL vials and compounded GLP-1 vials are common examples. A single-dose vial is different: CDC says it is for one patient and one injection, and the leftover should not be saved or pooled.
Step by step
- Clean the top. The first time, take off the plastic cap. Wipe the rubber stopper with an alcohol pad before each puncture. CDC's injection safety checklist lists disinfecting the stopper with alcohol before piercing it.
- Use a new needle and syringe. CDC says vials should be entered with a new needle and a new syringe, even for another dose for the same person.
- Fill the syringe with air. With the cap still on, pull the plunger back to the line for your dose.
- Push the air in. Put the needle through the stopper and push the air into the vial. MedlinePlus says this keeps a vacuum from forming; too little air makes the liquid hard to draw, and too much can force medicine back out of the syringe.
- Turn the vial upside down. Keep the needle tip in the liquid and pull the plunger to your dose line.
- Remove bubbles. With the tip still in the liquid, tap the syringe so bubbles rise and push them back into the vial. If there are many, push everything back and draw again slowly. Then check the dose again.
- Take the needle out. Do not leave a needle in the stopper for later doses; CDC lists this as an unsafe practice.
Reading the dose on the syringe
Syringes are marked in mL (the same as cc) or, on insulin syringes, in units. On a U-100 insulin syringe, 100 units equals 1 mL, so 10 units is 0.1 mL. To turn a dose in milligrams into a volume you need the vial's strength: a 200 mg/mL testosterone vial holds 100 mg in 0.5 mL. The reconstitution calculator and the U-40 vs U-100 guide show the math for mixed vials.
How long an opened vial lasts
CDC says an opened multi-dose vial should be dated and thrown away within 28 days unless the manufacturer states another date, and that this date should never go past the printed expiration date. FDA gives the same 28-day guidance for compounded GLP-1 vials and adds that the vial should be thrown away after that even if medicine is left. The rule is about contamination risk, which rises each time the stopper is punctured, not about the medicine running out.
CDC also says multi-dose vials should be assigned to one person whenever possible, and a used needle or syringe should never go back into a vial.
Logging the open date next to each dose drawn from the vial makes the 28-day mark easy to see. Dose Track stores each vial with its open or mix date and counts down what is left.
Read more on Dose Track: Multi-dose vial (glossary) · Beyond-use date · Coring · Sterile technique guide · How to reconstitute a peptide · How long mixed peptides last
General education drawn from labels, public health agencies and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your medicine are the final word. Questions for other users? Ask in the
Dose Track community.
Why do you push air into the vial first?+
MedlinePlus says it keeps a vacuum from forming. With too little air the medicine is hard to draw out; with too much, the medicine can be forced back out of the syringe.
Can I reuse a needle to draw a second dose from the same vial?+
No. CDC says to enter a vial with a new needle and a new syringe every time, even for another dose for the same person.
How long can I use a multi-dose vial after opening it?+
CDC says to date it when opened and throw it away within 28 days unless the manufacturer states a different date. FDA gives the same 28-day guidance for compounded GLP-1 vials.
What if I see bits or cloudiness in the vial?+
MedlinePlus says to check for color changes, floating pieces or cloudiness before drawing. Ask your pharmacist before using a vial that looks different. One exception is in the Depo-Testosterone label: crystals from cold storage should redissolve when the vial is warmed and shaken.