Handling & safety guide · chapter 06

Reconstitution: mixing a dry vial

Nine numbered steps of clean technique for turning a freeze-dried powder into a solution, each with a picture.

General information, not medical advice. Approved drugs: follow your prescriber and the product's instructions for use.

Reconstitution means adding a sterile liquid (the diluent) to a freeze-dried powder so it can be drawn into a syringe. Each needle puncture and each exposed surface is a chance to put bacteria into a vial that will then sit in your fridge. The steps below are standard aseptic habits adapted from clinical guidance and approved product instructions [1][2][3][4]. They lower the risk of contamination. They cannot make a kitchen or bathroom into a sterile pharmacy, and they do nothing about what is actually in the vial.

If your product has its own instructions for use, follow those and ignore this page where the two differ. Approved kits specify the exact diluent and volume and say to use only the diluent supplied [3][5].

Before you start

The diluent decides how long the vial can be kept.

  • Bacteriostatic water for injection contains 0.9% benzyl alcohol as a preservative and is packaged for repeated withdrawals [6]. It must never be used for newborns, and its label says to use it in pregnancy only if clearly needed [6].
  • Sterile water for injection has no preservative. Anything mixed with it is single use: inject once, discard the rest [5][7].
  • Tap water, bottled water, boiled water and household distilled water are not sterile and are never acceptable.

Decide the volume first. Work out how much diluent to add, and what concentration that gives, on the mixing math page before you open anything.

What you need (generic descriptions):

  • the sealed vial of powder and a sealed vial of diluent
  • one new sterile syringe with needle, large enough for the diluent (for example 1 mL or 3 mL)
  • individually wrapped 70% isopropyl alcohol swabs
  • a sharps container
  • a pen or label for the date

The steps

Step 1 — Prepare a clean surface and lay everything out

Choose a table or counter away from food preparation, pets, open windows and fans. Wipe it clean and let it dry. Lay out the supplies, still in their wrappers, so you do not have to rummage for anything with a needle in your hand. Clinical guidance calls for medicines to be prepared in a clean, dedicated area [1].

A clean workspaceA tidy, well-lit tabletop seen from above. Laid out in a row with space between them: a small vial of white powder, a larger vial of clear liquid, one wrapped syringe, two wrapped alcohol swabs, a marker pen, and a sharps container at the edge. Nothing else on the table. A faint outline of a wiped area suggests the surface was just cleaned.
Step 1 A clean workspace

Step 2 — Wash your hands

Wash with soap and running water, including between the fingers and under the nails, and dry with a clean towel or paper towel [4][8]. Hand hygiene is a core requirement of injection-safety standards [2]. After washing, touch only your supplies.

Hand washingTwo hands lathered with soap under a running tap, foam between the fingers. A clean paper towel waits beside the sink. Simple and calm, no clock or timer.
Step 2 Hand washing

Step 3 — Check both vials and let them reach room temperature

Read both labels: right substance, right amount, not expired. Look at the powder and the diluent against the warning signs checklist; the diluent must be clear with nothing floating in it [4][6]. If the vials came out of a fridge or freezer, stand them on the clean surface until they no longer feel cold, so that moisture does not condense on the stoppers and the powder dissolves more easily. Do not warm them with hot water, a radiator or a microwave: heat damages peptides [9].

Inspect and waitA hand holds the powder vial up to eye level against a plain light background, label visible as blank lines. The diluent vial stands on the table beside it. A small thermometer icon reading "room temperature" (no numbers needed) and a few drops of condensation fading from the glass show the vials warming up.room temp
Step 3 Inspect and wait

Step 4 — Remove the caps and swab both stoppers

Flip off the plastic caps. Wipe each rubber stopper firmly with a fresh alcohol swab, one swab per vial, and let the alcohol dry on its own. Do not blow on it, fan it or touch the stopper afterwards [2][4]. Do the same before every later puncture: a stopper is not sterile just because it was under a cap.

Swab the stopperClose-up of the top of a vial with its plastic cap flipped off and lying beside it. A fingertip presses a folded alcohol swab onto the grey rubber stopper. A second vial behind it already has small "drying" lines rising from its stopper.
Step 4 Swab the stopper

Step 5 — Draw up the diluent

Unwrap the syringe without touching the needle. Pull the plunger back to the volume you plan to draw, push the needle straight through the centre of the diluent stopper, and inject that air into the vial; this stops a vacuum forming and makes the liquid easier to draw [4]. Turn the vial upside down, keep the needle tip in the liquid, and pull the plunger slowly to your planned volume. Tap out large bubbles and correct the volume before withdrawing the needle [4].

Draw the diluentThe diluent vial held upside down in one hand, syringe below it with the needle through the stopper and its tip inside the liquid. The plunger is partly pulled back and the barrel is filling. A small arrow shows the plunger moving down. Syringe markings are simple tick marks without numbers.
Step 5 Draw the diluent

Step 6 — Add the diluent slowly, down the inside of the glass

Push the needle through the centre of the powder vial's stopper. Tilt the vial slightly and aim the needle at the inner glass wall, not at the powder. Press the plunger slowly so the liquid runs down the glass and pools at the bottom. Some vials are sealed under partial vacuum and will pull the liquid in on their own: hold the plunger back so it still trickles. A hard jet onto the powder makes foam, and foaming and agitation are known to damage peptides at the surface between liquid and air [9][10].

Down the glassSide view of the powder vial tilted about 30 degrees. The needle enters through the stopper and its tip rests near the inner wall. A thin stream of liquid runs down the inside of the glass and collects beneath the white powder, which is only partly wetted. An arrow traces the stream along the wall.
Step 6 Down the glass

Step 7 — Swirl gently. Do not shake

Withdraw the needle and put the syringe straight into the sharps container without recapping it. Then move the vial in slow circles, or roll it between your palms, until the powder has dissolved. Approved products say this in so many words: "swirl" or roll gently, "do not shake" [3][5]. If it has not all dissolved, stand the vial down for a few minutes and swirl again. Patience, not force.

Swirl, don't shakeA hand holds the vial upright by its neck; a circular arrow around the base shows a slow swirling motion, with the liquid forming a gentle whirl. In a small inset, a vial being shaken up and down with foam inside is crossed out.
Step 7 Swirl, don't shake

Step 8 — Inspect the solution

Hold the vial up to the light. It should be clear, with no particles, strands or cloudiness, and the colour the product is supposed to be (most are colourless) [3][6]. A few small bubbles or a little foam that settles within minutes is normal. Anything else: see troubleshooting, and if it does not clear, discard.

Check for clarityA vial of clear liquid held up in front of a bright window or lamp, light passing cleanly through it. Beside it, two small crossed-out examples: one vial with cloudy liquid, one with visible specks.
Step 8 Check for clarity

Step 9 — Label, date, refrigerate and tidy up

Write on the vial: the substance, the concentration (for example "5 mg/mL"), the date mixed and the discard date [1][4]. Put it in the fridge unless the product's label says otherwise (see storage). Check the syringe is in the sharps container, throw away the wrappers and swabs, and wash your hands again.

Label and storeA hand writing on a small label stuck to the vial; the label shows blank lines for name, strength, "mixed" date and "discard" date. Behind it, an open refrigerator shelf with a small box where the vial will go, and the sharps container on the counter with the used syringe dropped inside.namestrengthmixeddiscard
Step 9 Label and store

Things that are never part of the process

  • Reusing a syringe or needle, even "just for the water" [1].
  • Leaving a needle in the stopper as a permanent access port [1].
  • Mixing two different products in one vial or one syringe. Compatibility is unknown, and approved labels forbid it for their own products [8].
  • Topping up an old vial with fresh powder or fresh diluent.
  • Filtering or "rescuing" a cloudy solution.

Sources

Checked 13 November 2026.

  1. U.S. Centers for Disease Control and Prevention. "Preventing Unsafe Injection Practices." https://www.cdc.gov/injection-safety/hcp/clinical-safety/index.html
  2. World Health Organization. "WHO Best Practices for Injections and Related Procedures Toolkit" (2010), chapter 2, "Best practices for injection." https://www.ncbi.nlm.nih.gov/books/NBK138495/
  3. Tesamorelin for injection (Egrifta WR), US prescribing information and instructions for use, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=839334d3-8c1d-4c26-9036-2ab524a6ea75
  4. MedlinePlus Medical Encyclopedia. "Drawing medicine out of a vial." https://medlineplus.gov/ency/patientinstructions/000530.htm
  5. Tesamorelin for injection (Egrifta SV), US prescribing information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3d783378-b02d-4f19-99dd-0fc91a042224
  6. Bacteriostatic Water for Injection, USP (0.9% benzyl alcohol), US product labeling. (link not shown: non-primary host)
  7. American Society of Health-System Pharmacists. "The Pharmacist Guide to Assigning a Beyond-Use Date to a Compounded Sterile or Nonsterile Preparation" (summarising USP <797>). https://www.ashp.org/-/media/assets/pharmacy-practice/resource-centers/compounding/docs/The-Pharmacist-Guide-to-Assigning-a-Beyond-Use-Date.pdf
  8. Tirzepatide (Zepbound) single-dose vial, Instructions for Use (revised April 2026). (link not shown: non-primary host)
  9. Nugrahadi PP, Hinrichs WLJ, Frijlink HW, Schöneich C, Avanti C. "Designing Formulation Strategies for Enhanced Stability of Therapeutic Peptides in Aqueous Solutions: A Review." Pharmaceutics. 2023;15(3):935. https://doi.org/10.3390/pharmaceutics15030935
  10. Zapadka KL, Becher FJ, Gomes dos Santos AL, Jackson SE. "Factors affecting the physical stability (aggregation) of peptide therapeutics." Interface Focus. 2017;7(6):20170030. https://doi.org/10.1098/rsfs.2017.0030