Bacteriostatic water is the standard diluent – sterile water preserved with 0.9% benzyl alcohol, which is what allows a vial to be entered repeatedly without microbial growth. A small number of compounds dissolve poorly at neutral pH and are better started in 0.6% acetic acid before diluting.
Choosing a diluent
| Diluent | When to use it |
|---|---|
| Bacteriostatic water | The default for almost everything in the range. The preservative allows repeated vial entry. |
| 0.6% acetic acid | Sequences that stay cloudy or partially undissolved in neutral water. Use for the initial dissolution step, then dilute with bacteriostatic water to the working concentration. |
| Sterile water / 0.9% saline | Single-use preparations where the preservative is undesirable. |
The technique matters more than most people expect
- Allow the sealed vial to reach room temperature before opening, so condensation does not form inside.
- Wipe both stoppers with an alcohol swab and let them dry.
- Draw your diluent.
- Run it slowly down the inside wall of the vial rather than firing it directly onto the powder cake.
- Swirl gently until the solution is clear. Never shake.
- Label with the compound, concentration and date.
Agitation shears longer peptide chains. The larger compounds – Tesamorelin, IGF-1 LR3, TB-500 – are the most vulnerable, and a vigorously shaken vial can lose material before the first measurement is taken. If foam forms, the technique was too aggressive.
How much diluent to add
This is a convenience decision, not a correctness one. The volume sets the concentration, and therefore how many units you draw for a given amount. More water makes small measurements easier to read on a syringe barrel; less water leaves more headroom in the vial.
The arithmetic is simple: concentration equals peptide mass divided by diluent volume. A 5mg vial reconstituted with 2ml gives 2.5mg/ml, or 2,500mcg/ml. Drawing 250mcg from that solution needs 0.1ml, which is 10 units on a U-100 syringe. Our reconstitution calculator does that arithmetic including the U-100 conversion.
After reconstitution
Store at 2-8°C, protect from light, and avoid repeated freeze-thaw cycles. Where the study design allows, aliquot into single-use volumes so the stock is thawed once rather than repeatedly.
Research Use Only. This guidance covers laboratory dilution planning. It is not dosing guidance and the compounds referred to are not for human or veterinary use.
Frequently asked questions
How much bacteriostatic water should I add?
It is a convenience decision rather than a correctness one. The volume sets the concentration and therefore how many syringe units a given amount works out to. More water makes small measurements easier to read on the barrel; less leaves more headroom in the vial. Our reconstitution calculator does the arithmetic either way.
Why must I never shake the vial?
Agitation shears longer peptide chains, so material is lost before the first measurement is taken. Run the diluent slowly down the inside wall and swirl gently until clear. If foam forms, the technique was too aggressive. Tesamorelin, IGF-1 LR3 and TB-500 are the most vulnerable.
When should I use 0.6% acetic acid instead of bacteriostatic water?
When a sequence stays cloudy or partially undissolved in neutral water. Use the acid for the initial dissolution step only, then dilute with bacteriostatic water to reach the working concentration.
Why bacteriostatic water rather than plain sterile water?
The 0.9% benzyl alcohol preservative is what allows a vial to be entered repeatedly without microbial growth. Plain sterile water is fine for a single-use preparation, but not for a multi-dose vial.
How long does a reconstituted vial last?
Store at 2-8°C, protected from light, and plan the work so the vial is used within the standard research window rather than frozen and thawed repeatedly. Aliquot into single-use volumes where the protocol allows.
Research Use Only. Everything on this page is written for laboratory and analytical contexts. Nothing here is dosing guidance, medical advice, or a suggestion of human or veterinary use.