This tool only converts the numbers you enter. It does not recommend a dose, a concentration, or a protocol. Your dose, your reconstitution volume, and your injection schedule come from the clinician who prescribed your peptide. If a result here does not match what your provider told you, stop and ask them before drawing up an injection.
Enter the vial size, water volume, and your prescribed dose to see the draw volume.
What peptide reconstitution actually does
Peptides like sermorelin ship as a freeze-dried (lyophilized) powder in a sealed vial. Reconstitution means adding a liquid, almost always bacteriostatic water, to dissolve that powder back into a solution you can draw into a syringe. The amount of water you add sets the concentration: the same 5 mg vial reconstituted with 1 mL of water is twice as concentrated as the same vial reconstituted with 2 mL, so the injection volume for an identical dose is different in each case. This is the calculation a peptide dosing calculator or peptide reconstitution calculator is doing under the hood.
Bacteriostatic water vs. sterile water
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which slows bacterial growth across the multiple punctures a multi-dose vial goes through over its use window. Sterile water for injection carries no preservative and is intended for a single immediate draw. Most compounding pharmacies dispense peptides for reconstitution with bacteriostatic water specifically because a vial is entered repeatedly; check the label your pharmacy sent, since it states which one to use for your specific prescription.
How to read a U-100 insulin syringe
Insulin syringes are marked in units, not milliliters. A U-100 syringe is calibrated so 100 units equal 1 mL of fluid, which is the standard syringe most US pharmacies dispense with peptide prescriptions. A U-50 syringe holds the same volume across 50 unit markings, and a U-40 syringe across 40, so the same 0.1 mL draw reads as 10 units on a U-100, 5 units on a U-50, or 4 units on a U-40. Using the wrong syringe scale against the wrong calculation is one of the most common peptide dosing mistakes, which is why this calculator lets you pick the syringe type you were actually given.
Storage after reconstitution
Once a peptide is reconstituted, it should go directly into a refrigerator between roughly 36 and 46 degrees Fahrenheit and stay out of direct light. Reconstituted peptides are not shelf-stable at room temperature and should never be frozen, since freezing degrades the peptide structure. Discard windows vary by peptide and by pharmacy; your compounding pharmacy\'s label or paperwork states the specific discard date for your vial.
Common reconstitution mistakes
- Reading milliliter markings on a syringe that is actually calibrated in units, or the reverse.
- Adding a different water volume than planned and forgetting to recalculate the concentration before drawing a dose.
- Reusing a syringe across multiple peptides, which risks cross-contamination between vials.
- Storing a reconstituted vial at room temperature or in a freezer instead of a refrigerator.
- Estimating a draw volume by eye instead of recalculating after changing vial size, water volume, or dose.
Frequently Asked Questions
What is bacteriostatic water and why is it used for reconstitution?
Bacteriostatic water is sterile water with 0.9% benzyl alcohol added. The benzyl alcohol inhibits bacterial growth, which is why bacteriostatic water is labeled for multi-dose vials that get punctured repeatedly over days or weeks. Plain sterile water has no preservative and is meant for a single draw, since it offers no protection against contamination once the vial is opened.
How do I read a U-100 insulin syringe?
A U-100 syringe is calibrated so that 100 units equal 1 mL. Each small line on the barrel is typically 1 unit on a 0.3 mL or 0.5 mL syringe, or 2 units on a 1 mL syringe. Draw the plunger to the line that matches the unit figure this calculator returns, not to a milliliter marking, since most insulin syringes are marked in units rather than mL.
How long does reconstituted peptide stay stable?
Most compounded peptides reconstituted with bacteriostatic water remain stable under refrigeration (36 to 46 degrees Fahrenheit) for roughly 20 to 28 days, though this varies by peptide and by your pharmacy's specific stability data. Your prescribing pharmacy or clinician gives you the storage window and discard date for your specific prescription. Do not freeze reconstituted peptide, and keep the vial out of direct light.
Is sermorelin FDA-approved?
No. Sermorelin sold today is compounded, prepared by a licensed 503A or 503B pharmacy under a prescription rather than manufactured as an FDA-approved drug product. Ask any provider you use about their pharmacy's sourcing and USP 797 compliance for sterile compounding.
What is the most common reconstitution mistake?
Confusing milliliters and units on the syringe, or using a different syringe size than the one the calculation assumed. A U-40 and a U-100 syringe hold the same volume differently: the same 0.1 mL draw is 10 units on a U-100 syringe but only 4 units on a U-40 syringe. Always confirm which syringe you were given before drawing a dose.
This calculator performs arithmetic only. It does not diagnose, treat, or recommend a dose, and nothing on this page is medical advice. Reconstitution volumes, dosing, and injection schedules must come from a licensed prescribing clinician. Sermorelin is a compounded peptide, not an FDA-approved drug product.