Beginner friendly · No math needed yet

How to reconstitute peptides

A simple visual guide to understanding BAC water, concentration and syringe measurements.

We'll use one easy example: a 10 mg vial + 1 mL BAC water.

Start here

Build your reconstitution example

Choose a compound and reference amount to personalize the guide below.

Step 1

Choose your compound

Step 2

What's in your vial?

Step 3

How much BAC water / diluent are you adding?

Suggested for this vial amount. You can choose a different volume.

Your example

No compound selected yet

10 mg

1 mL

10 mg/mL

Selected reference amount: none selected

Show My Guide

Section 1

First, let's understand what you have.

Three simple objects. That's all this page is about.

10 mg Research Vial

This vial contains 10 mg of material.

BAC Water

This is the liquid used in our example — 1 mL of it.

Liquid

1 mL Syringe

A full 1 mL syringe = 100 units.

1 mL = 100 units

The whole idea, in one picture

10 mg vial

1 mL BAC water

Prepared vial

10 mg in 1 mL

That's it.

The amount of material did not change. You simply added 1 mL of liquid to it, giving 10 mg/mL.

Step 1

Remove the vial caps

Flip off the plastic cap from both vials.

BAC Water vial

1.Cap on

2.Flip cap off

3.Rubber stopper exposed

Research vial

1.Cap on

2.Flip cap off

3.Rubber stopper exposed

The rubber stopper underneath stays in place. Do not remove it.

Step 2

Clean the rubber stoppers

Wipe the rubber stopper on both vials with an alcohol wipe.

WIPE HERE

BAC Water vial — rubber stopper

WIPE HERE

Research vial — rubber stopper

Let the tops dry before continuing.

Step 3

Draw 1 mL of BAC Water

Start with the BAC Water vial

Push the needle through the center of the rubber stopper

Turn the vial upside down, needle still inside

Pull the plunger back slowly

The syringe fills with BAC Water

Stop at the mark for your amount

Markings: 0 · 25 · 50 · 75 · 100 units

100 units = 1 mL

A 1 mL U-100 syringe cannot hold more than 1 mL.

Step 4

Add the 1 mL of BAC Water to the research vial

Push the needle through the center of the rubber stopper

Press the plunger and let the liquid run in

Let the liquid run down the inside of the glass.

GENTLY

Let the water run slowly down the glass.

NOT LIKE THIS

Don't blast the material with the water.

Step 5

Let it dissolve

Gently swirl. Don't shake.

1.Material at the bottom

2.Partly dissolved

3.Clear prepared solution

Gentle swirl

Move the vial in slow circles.

Hard shaking

Avoid shaking the vial.

Now your vial contains:

10 mg

1 mL

The 10 mg was already in the vial.
You added 1 mL of liquid.

Therefore: 10 mg ÷ 1 mL = 10 mg/mL

Section 8

How much material is this?

Tap a syringe marking to see what amount of material it represents.

This amount

= 1 mg

Draw to 10 units on your syringe

10 units = 0.10 mL

With your selected setup: 10 mg vial + 1 mL BAC Water

Want a different amount? Tap a syringe marking above to see how much material it represents.

These are mathematical conversions based only on the example you built above. They are not recommended amounts.

Three things to remember

mL = liquid volume

How much liquid there is.

Units = syringe markings

On a U-100 syringe, 100 units = 1 mL.

mg = amount of material

How much material is in the vial.

They are different measurements.

Still confused? These are different things.

10 mg Amount of material in the vial
1 mL Amount of liquid added
100 units A syringe measurement equal to 1 mL on a U-100 syringe
10 mg/mL The final concentration in this example

Section 11

What if you add more water?

Every example below uses the same 10 mg vial.

10 mg + 1 mL

Final concentration

10 mg/mL

10 mg + 2 mL

Final concentration

5 mg/mL

10 mg + 5 mL

Final concentration

2 mg/mL

The amount of material in the vial does not change when you add liquid.

Adding more liquid changes the concentration.

10 mg + 1 mL 10 mg/mL

10 mg + 2 mL 5 mg/mL

10 mg + 5 mL 2 mg/mL

Think you've got it?

You have a 10 mg vial and add 1 mL BAC Water. What's the concentration?

Got the idea?

Now use the CompoundWiki calculator to work out your own concentration.

Open Reconstitution Calculator

The calculator performs concentration and unit-conversion math. It does not recommend an amount or dosing schedule.

Frequently asked questions

What is reconstitution?

Adding a liquid — usually bacteriostatic water — to a freeze-dried powder so it becomes a solution that can be measured and drawn into a syringe.

What is BAC Water?

Bacteriostatic water: sterile water containing 0.9% benzyl alcohol as a preservative, so a vial can be entered more than once.

What does "lyophilized" mean?

Freeze-dried. The liquid was removed under vacuum at low temperature, leaving a stable powder.

Is 1 mL always the correct amount?

No — 1 mL is just the example used throughout this page. The right amount depends on your vial and the concentration you want.

Is 1 mL the same as 100 units?

On a standard U-100 insulin syringe, yes. That scale is specific to U-100 syringes.

Why does the vial pull the water in?

Many lyophilized vials are sealed under slight vacuum, so the vial draws some liquid in on its own.

Should I shake the vial?

No — swirl gently. Shaking can damage the peptide structure.

What if the material doesn't dissolve immediately?

Give it a few minutes at room temperature and swirl gently again.

Why isn't my peptide dissolving after reconstitution?

Cold liquid, too little diluent or a degraded vial are the usual causes. If it stays cloudy or gritty, do not use it.

How long does a peptide take to dissolve after reconstitution?

Usually seconds to a few minutes with gentle swirling.

Why are there particles or flakes in my reconstituted peptide?

It may not have fully dissolved, or the solution has degraded. Particles that persist after swirling mean the vial should not be used.

Why is my peptide gelling up after reconstitution?

Some peptides gel at high concentration. More diluent, added gently, usually prevents it.

Why is my peptide cloudy after reconstitution?

Cloudiness usually means incomplete dissolution or degradation. A correctly prepared solution is clear.

Why is my peptide foamy or bubbly after reconstitution?

Usually from injecting the water too fast, or shaking. Let it settle undisturbed for a few minutes.

What should a reconstituted peptide look like?

Clear and colorless, with no visible particles, cloudiness or foam.

Why is there powder stuck to the side of my peptide vial?

Static can hold powder to the glass. Swirl gently so the liquid reaches it.

What does concentration mean?

How much material sits in each mL of liquid — expressed as mg/mL.