Guide · For research
How to mix (reconstitute) a peptide vial
If you search online, you'll find many opinions on how to turn peptide powder into a solution ready for research use. This guide covers the two main methods.
Method 1 (pen) is the recommended method. It takes a little more setup, but once it's done each dose is just a turn of a dial.
Method 2 (syringe) is quicker to set up and suits people who don't want to assemble their own pen.
The pen method is the recommended method because of its accuracy. It takes an extra step or two compared with the syringe method, but in return you get a pen that delivers a finely tuned dose.
Find a clean working surface
A flat table works. Make sure the area is wiped down and clean.
Lay out your materials
Set out the peptide vial, bacteriostatic water, 3 mL cartridge and the two 23-gauge mixing syringes.
Prepare the vials and cartridge, and sanitize
Remove the 3 mL cartridge from its packaging and uncap the bacteriostatic water and the peptide vial. With a single swipe of an alcohol pad, sanitize the top of each.
Draw 2.1 mL of bacteriostatic water
Make sure the 23G needle is tightly fastened to the 23G mixing syringe. Pull back 2.1 mL of air, inject that air into the bacteriostatic water vial, then immediately draw back 2.1 mL of water.
Multi-use bacteriostatic water vials are zero-pressure systems. If you take liquid out, push in the same amount of air so you don't create a vacuum.
Good to knowWhy 2.1 mL? Some liquid is always lost during transfer (left behind in the vial and the 23G mixing syringe). Adding 2.1 mL leaves you with about 2.0 mL of usable solution, a round, practical volume to work with. The loss doesn't change the concentration: all of the peptide is dissolved in the full 2.1 mL, so always calculate doses using 2.1 mL.Add the water to the peptide vial
Slowly push the 23G mixing syringe’s needle through the rubber stopper of the peptide vial. You usually don't need to push the plunger. The vial's negative pressure pulls the water in on its own.
You'll use this 23G mixing syringe again shortly, so recap it safely and set it aside. Don't discard it yet.
Gently mix
Hold the vial between your palms and roll it gently until everything dissolves. Don't shake it, because shaking causes foaming and makes the solution harder to draw out. A little foam is fine and settles within a couple of minutes.
Draw out the solution
Insert the same 23G mixing syringe into the reconstituted peptide vial and turn the vial upside down. Keep the needle tip below the liquid line so you can draw out the full contents. Pull back firmly, since you're working against the vial's negative pressure. When you've drawn out as much as you can, recap the 23G syringe and set it aside.
Good to knowA little solution will stay in the vial. That's expected, because the 2.1 mL step allows for this loss.Fill the 3 mL cartridge
The cartridge is sealed. As you push liquid in, the air inside needs somewhere to go, so you use a second, separate needle as an air vent. Without it, pressure builds up, the solution is hard to push in, and it can spray back out.
- Make the vent needle. Take your second (unused) 23G syringe and remove its needle. You only need the needle; set the empty syringe aside.
- Insert the vent. Uncap that needle and push it straight through the cartridge's rubber stopper on its own, with no syringe attached. Leave it there the whole time you fill.
- Hold the cartridge upright, stopper on top, so the vent needle's tip stays above the liquid and only air escapes.
- Insert the filled 23G syringe in a different spot. Push the needle of the 23G syringe holding your solution through the stopper a few millimeters away from the vent: two needles, two separate holes. Don't attach the 23G syringe to the vent needle.
- Push slowly. As the solution goes in, air escapes through the vent. Going fast creates foam.
- Remove both needles once the 23G syringe is empty, and put them straight into a sharps container.
Good to knowCommon mistakes: using only one needle (pressure builds and the solution sprays back), or pushing the 23G syringe through the vent needle instead of its own hole. You need two needles in two separate holes.Load the cartridge into the pen
A pen has three parts: the injector end, the cartridge compartment and a cap. Remove the cap, unscrew the pen and place the filled cartridge in the compartment so the top of the cartridge sits at the very tip of the pen. Screw the pen back together.
Purge the air
The new cartridge will have an air pocket that must be removed before use. Attach a new needle tip and hold the pen upright with the needle pointing up.
Turn the dial to a small setting and push the button all the way in to force out the air. Repeat until no air is visible and a small drop of liquid appears at the tip. That means the pen is fully primed.
Good to knowTake your time here. Air left in the cartridge makes doses inaccurate.Work out your dose
Use the dosage calculator and choose Pen. It tells you how many units to dial. Enter 2.1 as the bacteriostatic water amount (what you added), not 2.0.
Store it in the refrigerator
Keep assembled pens in the refrigerator. Research use more than 3 months after reconstitution is not recommended.
The syringe method mixes the peptide with bacteriostatic water in its vial. You then draw each dose straight from the vial, either one at a time or all up front.
Find a clean working surface
A flat table works. Make sure the area is wiped down and clean.
Lay out your materials
Set out the peptide vial, bacteriostatic water, one 23-gauge mixing syringe and your U-100 syringes.
Prepare the vials and sanitize
Uncap the bacteriostatic water and the peptide vial. With a single swipe of an alcohol pad, sanitize the top of each.
Draw 2.1 mL of bacteriostatic water
Make sure the 23G needle is tightly fastened to the 23G mixing syringe. Pull back 2.1 mL of air, inject that air into the bacteriostatic water vial, then immediately draw back 2.1 mL of water.
Multi-use bacteriostatic water vials are zero-pressure systems. If you take liquid out, push in the same amount of air so you don't create a vacuum.
Good to knowWhy 2.1 mL? Some liquid is always lost during transfer (left behind in the vial and the 23G mixing syringe). Adding 2.1 mL leaves you with about 2.0 mL of usable solution, a round, practical volume to work with. The loss doesn't change the concentration: all of the peptide is dissolved in the full 2.1 mL, so always calculate doses using 2.1 mL.Add the water to the peptide vial
Slowly push the 23G mixing syringe’s needle through the rubber stopper of the peptide vial. You usually don't need to push the plunger. The vial's negative pressure pulls the water in on its own.
Gently mix
Hold the vial between your palms and roll it gently until everything dissolves. Don't shake it, because shaking causes foaming and makes the solution harder to draw out. A little foam is fine and settles within a couple of minutes.
Fill your U-100 syringes
You can fill every dose now by pre-filling U-100 syringes, or fill one U-100 syringe each time you need a dose. The 23G mixing syringe is only for preparing the vial; don't use it for doses.
To fill a U-100 syringe, remove its orange cap and push the needle through the rubber stopper of the reconstituted peptide vial. Turn the vial upside down and pull back gently until the black seal lines up with the number of units you need.
Good to knowWipe the top of the vial with alcohol before each new needle goes in.Work out your dose
Use the dosage calculator and choose Syringe. It tells you how many units to draw into your U-100 syringe. Enter 2.1 as the bacteriostatic water amount (what you added), not 2.0.
Store it in the refrigerator
Keep reconstituted peptides in the refrigerator, whether in the vial or in pre-filled U-100 syringes. Research use more than 3 months after reconstitution is not recommended.
Next: work out your dose
Enter your vial strength, the water you added and your dose. The calculator gives you the exact units to dial or draw.
Common questions about mixing peptides
How do you mix (reconstitute) peptides?
Wipe both vial tops with alcohol, draw 2.1 mL of bacteriostatic water with a 23G mixing syringe, and push it slowly into the peptide vial so it runs down the glass. Roll the vial gently until the powder dissolves; don’t shake it. Then fill a pen cartridge (Method 1) or draw doses with U-100 syringes (Method 2). The steps above walk through both methods with diagrams.
How much bacteriostatic water should I add to a 5 mg or 10 mg peptide vial?
There is no single correct amount. We recommend 2.1 mL: about 0.1 mL is lost during transfer, leaving roughly 2.0 mL of usable solution. You can add more or less (most peptide vials hold up to 3 mL); just enter the amount in the dose calculator.
Why 2.1 mL and not 2 mL?
Some liquid is always lost during transfer (left behind in the vial and the 23G mixing syringe). Adding 2.1 mL leaves about 2.0 mL of usable solution. All of the peptide is dissolved in the full 2.1 mL, so always calculate doses using 2.1 mL.
Can I use sterile water instead of bacteriostatic water?
Bacteriostatic water contains 0.9% benzyl alcohol, a preservative that limits bacterial growth when a vial is punctured more than once. Sterile water has no preservative and is meant for single use, so it isn’t suited to a vial you will draw from many times.
Should you shake a peptide vial?
No. Roll the vial gently between your palms until it dissolves. Shaking causes foaming and makes the solution harder to draw out. A little foam is fine and settles within a couple of minutes.
How long does a reconstituted peptide last?
Keep it in the refrigerator. Research use more than 3 months after reconstitution is not recommended. Throw away any solution that looks cloudy or discolored.
What does U-100 mean on a syringe?
U-100 means 100 units per mL, so 1 unit is 0.01 mL and a 1 mL syringe holds 100 units. Pens use the same units. The calculator converts a dose in mg or mcg into units.
What needles do I need to mix peptides?
A 23G syringe is used only for mixing (moving the water into the vial and, for the pen method, filling the cartridge). Doses are measured with U-100 syringes or a pen with new pen needle tips. Use a new sterile needle every time.