Mixing, drawing, syringe gauges and storage — walked through in plain language, with an illustration of the actual pose at every step.
Before beginning, gather the following:
For the most accurate and sterile process, use two different sterile syringes — one to mix the vial, and a separate one to measure each dose.
A larger sterile syringe, used only for transferring bacteriostatic water into the vial. Match it to the volume you're adding:
| Volume being added | Recommended syringe |
|---|---|
| 1–3 mL | 3 mL syringe |
| 3–5 mL | 5 mL syringe |
| 5–10 mL | 10 mL syringe |
A larger barrel makes measuring the bacteriostatic water considerably easier and more accurate than trying to do it with an insulin syringe.
Nearly every peptide protocol uses an insulin syringe for the dose itself. They're built specifically for small, precise volumes, and they come fitted with thin-gauge needles suited to subcutaneous injection. They're inexpensive and widely available, and because the needle is permanently fixed to the barrel rather than screwing on, they have very little dead space — the small pocket of liquid that otherwise gets trapped in the hub and wasted on every single draw.
Two separate things are printed on an insulin syringe, and confusing them is where most dosing mistakes begin: its capacity (how much liquid the barrel physically holds) and its unit scale (what each tick mark actually represents).
Gauge (G) describes how thick the needle is, and the numbering runs backwards — a higher number means a thinner needle. Insulin syringes almost always come in 29G, 30G, or 31G, all of which are fine for subcutaneous use. The trade-off is small but real:
| Gauge | Relative thickness | Trade-off |
|---|---|---|
| 29G | Thickest of the three | Fastest to draw and push, slightly more noticeable |
| 30G | Middle ground | The most common all-round choice |
| 31G | Thinnest | Least sensation, slowest to draw |
Needle length matters less than gauge for subcutaneous work — most insulin syringes come with a short needle in the 4–13 mm range (often listed as 5/16" or 1/2"), and any of those reach subcutaneous tissue.
U-100 means the syringe is calibrated so that 100 units equals 1 mL — so one unit is 0.01 mL. That ratio stays the same no matter which barrel size you buy; only the total capacity and the spacing of the marks change:
| Barrel capacity | Total units | One unit equals |
|---|---|---|
| 0.3 mL | 30 units | 0.01 mL |
| 0.5 mL | 50 units | 0.01 mL |
| 1.0 mL | 100 units | 0.01 mL |
A smaller barrel spreads the same units further apart, which makes small doses easier to read accurately — a 30-unit syringe is easier to measure 8 units on than a 100-unit one. Pick the smallest barrel that still holds your dose. The Peptide Calculator lets you choose between 30, 50, and 100-unit syringes and shows your draw marked on that exact scale.
Whichever you use, always start each draw with a fresh, unused syringe — reusing one dulls the needle and risks contaminating the vial.
Bacteriostatic water is the default choice for a reason: it contains a small amount of benzyl alcohol as a preservative, which lets a reconstituted vial be used repeatedly over several weeks instead of needing to be discarded after one draw.
Sterile water (without the preservative) works for a single use only — once opened, it should be treated as a one-time-use vial rather than stored and redrawn from.
Saline is sometimes used as an alternative, though bacteriostatic water remains the more common and widely available option. Whichever you use, it should be a pharmaceutical-grade diluent intended for injectable reconstitution — never tap water, distilled water, or anything not labeled for that purpose.
There's no single "correct" amount — it's a trade-off between concentration and how precisely you can measure small doses. Adding less water gives you a more concentrated solution (useful for very small microgram doses), while adding more water gives you a more dilute solution that's easier to measure accurately on a syringe when doses are larger.
Most people land somewhere between 1 mL and 3 mL for a typical vial, adjusting based on their target dose and syringe size. Rather than guessing, enter your vial size and target dose into the Peptide Calculator — it will show you the exact syringe unit mark to draw to for whatever water amount you choose.
These are illustrative only — your actual vial size, target dose, and syringe will differ. Plug your own numbers into the Peptide Calculator for an exact draw volume, or check the Dosage Chart for typical ranges by peptide.
The powder is taking a long time to dissolve
Some peptides simply dissolve more slowly than others. Let the vial sit longer and gently swirl it every minute or two — avoid shaking. If it still hasn't cleared after 10–15 minutes, it may be worth checking that the diluent used was appropriate.
The solution looks cloudy
Cloudiness right after mixing usually clears as the powder finishes dissolving. Persistent cloudiness afterward can indicate a problem with the peptide itself — when in doubt, don't use it.
The liquid has changed color
Most reconstituted peptides should stay clear or match their expected baseline appearance. A noticeable color shift, especially over time in storage, is a sign the vial may no longer be good.
I think I added the wrong amount of water
If you're not confident in the diluent volume you added, it's safer to discard and start over with a fresh vial than to guess at doses from an uncertain concentration.
There's foam on top after mixing
Foam usually comes from injecting the water too forcefully or swirling too vigorously. It typically settles on its own after a few minutes of the vial sitting still.
The rubber stopper looks worn out
Repeated needle insertions gradually wear down a stopper. If it looks visibly damaged or no longer reseals cleanly, that vial shouldn't be drawn from again.