If you have a peptide vial in front of you and have never mixed one before, this walkthrough is for you. Each step is short, and the math is worked out for you. It covers mixing only: how or whether to use any compound is a question for the product labeling and a qualified professional. If you run into an unfamiliar word along the way, look it up in our peptide glossary.
Step 1: Know what is in your vial
A peptide usually arrives as a small puck of white powder at the bottom of a sealed glass vial. The powder is freeze-dried (lyophilized), which keeps it stable until you add liquid.
- Read the label first. Note the compound name and the total amount in the vial, usually in mg. That number drives all of the math later.
- Check the lot number and expiration date. A vial without them gives you no way to judge its age.
- Leave the cap and stopper in place. The water goes in through the rubber stopper with a needle. The vial is never opened.
Tip: The powder can look like a thin film or be almost invisible. That is normal for small amounts.
Step 2: Gather your supplies
Lay everything out before you start so you are not hunting for something halfway through. For a first mix you need:
- Bacteriostatic water. Sterile water with 0.9% benzyl alcohol, which lets the vial be entered more than once.
- A mixing syringe. A 1 mL to 3 mL syringe for drawing the water and adding it to the vial.
- U-100 insulin syringes. These measure in units once the peptide is mixed.
- Alcohol prep pads. For wiping both rubber stoppers.
- A label or marker. For writing on the vial when you are done.
- A sharps container. For used needles and syringes.
Our checklist of peptide reconstitution supplies shows each item in one place.
Never use tap or bottled drinking water. Neither one is sterile, and both can introduce bacteria and minerals into the vial.
Step 3: Decide how much BAC water to add
This is the step beginners worry about most, but the math is simple. The amount of water you add sets the concentration, meaning how much peptide is in each unit on the syringe.
- Concentration = total mg in the vial ÷ mL of water added.
- Per unit = concentration ÷ 100, because a U-100 syringe holds 100 units per mL.
Worked example: a 5 mg vial mixed with 2 mL of BAC water gives 2.5 mg/mL, which is 2,500 mcg per mL. Divide by 100 and each unit on the syringe holds 25 mcg. An example amount of 250 mcg would then read as 10 units.
Adding more water makes each unit weaker; adding less makes it stronger. There is no single correct volume. Pick one that gives numbers you can read easily on your syringe. The BAC water for peptides calculator does this math for any vial size.
Write your numbers down before you mix: vial mg, water mL, and what one unit equals. You will need them for the label in step 7.
Step 4: Set up a clean workspace
- Wash your hands with soap and water.
- Work on a clean, dry, flat surface with good light.
- If a vial has been in the fridge, let it reach room temperature unless its label says otherwise.
- Remove the plastic caps and wipe the rubber stopper on the peptide vial and on the BAC water vial with an alcohol prep pad. Let both air-dry.
After wiping, do not touch the stoppers or the needle. If you do, wipe the stopper again with a fresh pad.
Step 5: Add the water slowly
- Draw the amount of BAC water you chose in step 3 into the mixing syringe.
- Push the needle through the center of the peptide vial’s stopper.
- Angle the needle so the water runs down the inside wall of the glass instead of spraying straight onto the powder.
- Press the plunger slowly. Some vials are sealed under a slight vacuum and will pull the water in on their own. Let it go at its own pace.
- Withdraw the needle and place the syringe in the sharps container.
Slow is better than fast. A hard stream onto the powder can cause foaming.
Step 6: Swirl gently until it dissolves
Gently swirl the vial, or roll it between your palms, until the powder is completely dissolved. This can take anywhere from a few seconds to several minutes. If powder is still visible, set the vial down for a few minutes and swirl again.
- Do not shake it hard. Vigorous shaking creates foam and bubbles.
- Never heat the vial to speed things up.
- Look at the result. A properly dissolved solution is usually clear. If it stays cloudy or has particles floating in it, check the product labeling before going any further.
Step 7: Label the vial and store it
Label the vial right away, before it goes anywhere. Write it by hand or print a neat sticker with our free vial label maker. Include:
- the compound name
- how much BAC water you added
- what one unit equals (from step 3)
- the date you mixed it
Store the mixed vial upright in the refrigerator (about 36–46°F, or 2–8°C) and away from light, unless its label says otherwise. How long a mixed peptide lasts depends on the compound, so check the product labeling. The opened BAC water vial follows the common 28-day rule, which our BAC water storage and shelf life guide explains.
Tip: The free Peptide Shot Tracker on this site can keep a private record of the date you mixed each vial.
Common beginner mistakes to avoid
- Using the wrong liquid. Tap water, bottled water, and anything not sterile are never substitutes for BAC water.
- Shaking the vial hard. Swirl or roll it gently instead.
- Heating the vial. Give the powder time to dissolve at room temperature.
- Mixing up mg and mcg. 1 mg is 1,000 mcg. Getting this wrong throws every number off by 1,000. See our mg to mcg conversion chart.
- Using a syringe that is not U-100. The units math above only works on U-100 insulin syringes.
- Skipping the label. A week later, you will not remember how much water went into which vial.
Where to go next
Once your first mix goes smoothly, our full guide on how to reconstitute peptides goes deeper on each step, including worked examples for different vial sizes.
Frequently Asked Questions
What does it mean to reconstitute a peptide?
It means adding a sterile liquid, usually bacteriostatic water, to the freeze-dried powder in a peptide vial so it dissolves into a solution that can be measured with a syringe.
How much BAC water should a beginner add to a peptide vial?
There is no single required amount. Many people add 1 to 3 mL and choose the volume that gives easy numbers on a U-100 syringe. For example, 2 mL in a 5 mg vial gives 25 mcg per unit.
Should you shake a peptide vial after adding water?
No. Swirl the vial gently or roll it between your palms until the powder dissolves. Hard shaking creates foam, and heat should never be used to speed things up.
Can you use tap or bottled water to reconstitute peptides?
No. Tap and bottled water are not sterile. Bacteriostatic water is the usual choice because its 0.9% benzyl alcohol allows a vial to be entered more than once.
Why is my reconstituted peptide cloudy?
Some powders take a few minutes to fully dissolve, so let the vial sit and swirl it again. If the solution stays cloudy or has particles in it, check the product labeling before going any further.
How should a mixed peptide vial be stored?
Upright in the refrigerator, away from light, and labeled with the date it was mixed, unless the product label says otherwise. How long it lasts depends on the compound.