Before you start
What You'll Need
Put everything on a clean, flat surface before you start. If you're doing this for the first time, that simple setup keeps you focused on one vial and one step at a time.
- Peptide vialThis is the small vial holding the freeze-dried powder. Read the vial amount in mg before you begin; you will use that number again for the calculator.
- Bacteriostatic water (BAC water)BAC water is sterile water with a preservative. Use it only when your vial’s label says BAC water is the liquid to use.
- U-100 insulin syringeThis is the small syringe with unit marks. A 0.3 mL syringe has 30 units, a 0.5 mL syringe has 50 units, and a 1 mL syringe has 100 units.
- Alcohol swabsUse a fresh swab on each rubber stopper before you draw or add liquid. Let the stopper air-dry after wiping it.
- A pen or labelWrite down the mix date, how much water you added, and the concentration. You will be glad you did when you come back to the vial later.
Step by step
How to Reconstitute Peptides
Take your time with the first mix — the same steps will feel quick the next time.
Read your vial first.Find the vial amount, the liquid it names, and how much liquid it says to add. Those are the only mixing numbers you need before you touch a syringe.
Set up and wipe the stoppers.Place the peptide vial, the listed liquid, syringe, and alcohol swabs on your clean surface. Wipe both rubber stoppers with fresh swabs, then let them dry.
Draw the liquid slowly.Pull the syringe plunger back to the amount from Step 1. Move slowly so you can see the unit line clearly and spot bubbles before they get in the way.
Add the liquid down the inside wall.Put the needle through the peptide-vial stopper and point the stream toward the glass wall, rather than straight at the powder. A slow stream lets the liquid spread around the powder without a rush of bubbles.
Swirl gently.Roll the vial in a small circle until the powder has dissolved. Skip the hard shake: it makes foam and bubbles that hide what is happening. If your product gives a different mixing method, use that method.
Look, then write it down.Compare the dissolved liquid with the appearance described for your product. Write the date, the water amount, and the concentration on the vial or a nearby note before you put it away.
Pause if something looks wrong. A damaged seal, unexpected color, particles, or powder that will not dissolve is a reason to stop and ask the supplier or pharmacy about that vial.
The simple math
How to Calculate Your Concentration
Once you know the amount in your vial and how much water you added, you can calculate concentration. Concentration simply means how much peptide is in each mL of liquid. Use mg/mL here: it matches the mg number most vial labels use and the main concentration unit in the calculator.
One extra conversion is useful when you see a smaller amount written in mcg: 1 mg equals 1,000 mcg. So 5 mg/mL is the same concentration as 5,000 mcg/mL. On a U-100 syringe, 100 units equals 1 mL, so 10 units equals 0.1 mL. That’s it.
Example with assumed values — math only
Assume a 4 mg vial is mixed with 2 mL of water
4 mg ÷ 2 mL = 2 mg/mL. If you need mcg, multiply by 1,000: 2 mg/mL = 2,000 mcg/mL. At that assumed concentration, 10 U on a U-100 syringe is 0.1 mL, which contains 0.2 mg, or 200 mcg. These are assumed numbers for learning the math, not a setup for your vial.
Example with assumed values — math only
Assume a 10 mg vial is mixed with 2 mL of water
10 mg ÷ 2 mL = 5 mg/mL, which is also 5,000 mcg/mL. Different vial and water numbers can give you a different concentration — that is why entering your own numbers matters.
Common Mistakes to Avoid
Most mistakes happen before the math. Knowing how to reconstitute peptides means keeping these small details in mind from the start.
- Guessing the water amount. The amount of water changes the concentration. A number from someone else’s vial cannot tell you what your own vial needs.
- Mixing up mg, mcg, mL, and units. They are four different things: mg and mcg are peptide amount; mL and units are liquid volume. Write the unit beside every number.
- Using the wrong liquid. BAC water, sterile water, and saline are different liquids. The name on your vial is more useful than a generic online chart.
- Adding the liquid too fast. A quick push makes extra bubbles. Slow and steady makes the vial easier to read and the powder easier to watch.
- Shaking the vial. Gentle swirling keeps foam down. That makes it easier to see when the dry powder has dissolved.
- Forgetting the mix date. Write it down while the vial is in your hand, along with the water amount and concentration.
Peptide Reconstitution FAQ
How much bacteriostatic water should I add?
Add the amount listed for your vial. That number sets the concentration, which then sets what each U-100 syringe unit represents. The calculator can turn that number into clear mL and unit math.
What does 10 units mean on a U-100 syringe?
On a U-100 syringe, 100 units equals 1 mL, so 10 units equals 0.1 mL. Units measure liquid volume. How much peptide is in that 0.1 mL depends on the concentration you made.
How do I know how many units to draw?
Start with three numbers: the total amount in your vial, how much water you added, and the amount you want to convert. Put those numbers into the Peptide Calculator to see the matching mL and U-100 units.
Can I shake a peptide vial?
Swirl the vial gently instead of shaking it. Gentle swirling helps the liquid reach the dry powder without filling the vial with foam and bubbles.
Related Resources
Turn a dry vial and desired amount into a suggested water volume and U-100 units
Peptide Reconstitution CalculatorTurn a known concentration into mL and units
Peptide Dosage Calculator