Quick answer: Concentration = vial size (mg) ÷ bacteriostatic water (mL). Units to draw = (dose ÷ concentration) × 100. A 10 mg vial in 2 mL of BAC water is 5 mg/mL, so a 2.5 mg dose = 50 units on a U-100 syringe. Enter your own vial size and water in the calculator above to see your exact numbers.
The reconstitution formula
Reconstitution turns a lyophilized (freeze-dried) GLP-1 peptide vial into an injectable solution by adding bacteriostatic water. The volume of water you add does not change your dose in milligrams — it changes the concentration, which is what decides how many units you draw on the syringe. Two steps get you from a vial to a syringe:
Worked example
Take a 10 mg vial and add 2 mL of bacteriostatic water. That gives 10 ÷ 2 = 5 mg/mL. For a 2.5 mg dose: (2.5 ÷ 5) × 100 = 50 units on a U-100 syringe (0.5 mL). Draw to the 50 mark. Keep the vial size and water the same and the units for every other dose scale from there — the reference table below does exactly that.
mg → units reference (10 mg vial)
| Dose | 10.0 mg/mL (10mg + 1mL) |
5.0 mg/mL (10mg + 2mL) |
3.33 mg/mL (10mg + 3mL) |
|---|---|---|---|
| 0.25 mg | 2.5 units (0.025 mL) | 5.0 units (0.05 mL) | 7.5 units (0.075 mL) |
| 0.5 mg | 5.0 units (0.05 mL) | 10.0 units (0.1 mL) | 15.0 units (0.15 mL) |
| 1 mg | 10.0 units (0.1 mL) | 20.0 units (0.2 mL) | 30.0 units (0.3 mL) |
| 2.5 mg | 25.0 units (0.25 mL) | 50.0 units (0.5 mL) | 75.0 units (0.75 mL) |
| 5 mg | 50.0 units (0.5 mL) | 100.0 units (1.0 mL) | 150.0 units (1.5 mL) |
| 10 mg | 100.0 units (1.0 mL) | 200.0 units (2.0 mL) | 300.0 units (3.0 mL) |
This static table shows a 10mg vial at three common water volumes. For any other vial size, use the interactive calculator above.
Standard titration ladders
Most people ramp their dose up gradually rather than starting at the target. These are the standard week-by-week ladders for each GLP-1 compound (every step is held for the interval shown). Use the dedicated titration calculator to build a schedule with your own start dose, target, and calendar dates.
| Compound | Ladder (mg) | Step interval |
|---|---|---|
| Retatrutide | 2 → 4 → 8 → 12 | every 4 weeks |
| Tirzepatide | 2.5 → 5 → 7.5 → 10 → 12.5 → 15 | every 4 weeks |
| Semaglutide | 0.25 → 0.5 → 1 → 1.7 → 2.4 | every 4 weeks |
Ladders are typical protocols, not medical advice — your provider may titrate faster or slower.
Frequently asked questions
How do you calculate peptide reconstitution?
Divide the total milligrams (mg) of peptide in the vial by the milliliters (mL) of bacteriostatic water you add. That gives the concentration in mg/mL. To find your dose in units, multiply the volume you need by 100. Example: a 10mg vial + 2mL water = 5mg/mL, so 20 units on a U-100 syringe = 1mg.
How much BAC water should I add to my peptide vial?
It depends on your desired concentration. More water means a lower concentration (easier to measure small doses accurately); less water means a higher concentration (fewer injections per vial). Common choices: 1-2mL for 5-10mg vials, 2-3mL for 10-30mg vials. Use the calculator above to see exact units for any combination.
What is the difference between BAC water and sterile water for reconstitution?
Bacteriostatic (BAC) water contains 0.9% benzyl alcohol as a preservative, preventing bacterial growth and allowing multi-dose use from the same vial for 28-60 days. Sterile water has no preservative, so reconstituted peptides must be used within 24 hours. Always use BAC water for multi-dose vials.
How do you convert mg dose to insulin syringe units?
First calculate your concentration: divide vial mg by mL of water added. Then units = (desired dose in mg ÷ concentration in mg/mL) × 100. Example: 10mg vial + 2mL water = 5mg/mL. For a 2.5mg dose: (2.5 ÷ 5) × 100 = 50 units on a U-100 syringe.
How long does reconstituted peptide last in the fridge?
When reconstituted with bacteriostatic water and stored at 36-46°F (2-8°C), most GLP-1 peptides remain stable for 28-60 days. Never freeze reconstituted peptides. Inspect for particles or discoloration before each use, and if the solution appears cloudy, discard it.
Per-compound calculators
This hub covers the generic math. For compound-specific vials, presets, and units charts, use the dedicated calculators:
| Compound | Reconstitution | Dose → units | Titration |
|---|---|---|---|
| Retatrutide | Reconstitution | Units | Titration |
| Tirzepatide | Reconstitution | Units | Titration |
| Semaglutide | Reconstitution | Units | Titration |
Safety: This tool is educational only. Always double-check your own math and follow a licensed provider's instructions before injecting. Last reviewed 2026-06-10.