How the Formula Works

The reconstitution formula is straightforward:

    mL of bacteriostatic water = Vial size (mg) ÷ Target concentration (mg/mL)

    Example: 5mg vial at 2.5 mg/mL → 5 ÷ 2.5 = 2.0 mL of bacteriostatic water

The calculator above applies this formula automatically and also calculates your draw volume based on your prescribed dose — so you know exactly how many units to pull for each injection.

Common Tirzepatide Concentrations

Your compounding pharmacy will specify which concentration your vial is prepared at. These are the most common combinations:

Vial Size	Bacteriostatic Water	Concentration	Common Use
5 mg	2.0 mL	2.5 mg/mL	Starting dose (2.5 mg weekly)
5 mg	1.0 mL	5.0 mg/mL	Escalation (5 mg weekly)
10 mg	2.0 mL	5.0 mg/mL	Mid-protocol doses
10 mg	1.0 mL	10 mg/mL	Higher doses (10–12.5 mg)
15 mg	1.5 mL	10 mg/mL	Maintenance / maximum
20 mg	2.0 mL	10 mg/mL	Multi-week supply

⚠️ Always use the concentration specified on your pharmacy label — not this table. Pharmacies may use different concentrations. Call your pharmacy if the label is unclear.

Common Reconstitution Mistakes

These are the errors GLP-1 patients make most often — each one can result in dramatically wrong doses or a contaminated vial.

Using sterile water instead of bacteriostatic water

Sterile water has no preservative. After the first draw, bacterial contamination is a real risk. Always use bacteriostatic water (0.9% benzyl alcohol).

Guessing the concentration

If you don't know your vial's concentration, you cannot calculate a correct dose. Check your pharmacy label — if unclear, call before mixing anything.

Injecting water directly onto the powder

Angle the needle so water runs down the side of the vial, not onto the powder. Direct injection causes foaming that can degrade the peptide.

Shaking instead of swirling

Shaking creates bubbles and can denature the peptide. Swirl gently between your palms until dissolved — it should be completely clear within 60 seconds.

Freezing the reconstituted vial

Freezing causes permanent protein aggregation. A frozen vial may look normal but is likely ineffective or unsafe. Discard any vial that has been frozen.

Not labeling the reconstitution date

Reconstituted tirzepatide should be used within 28 days when refrigerated. Without a date label, you have no way to know when to discard it.

Step-by-Step Process

Wash hands thoroughly with soap and water — at least 20 seconds
Swab both vial tops with separate alcohol swabs — allow to air dry 10–15 seconds
Draw the calculated volume of bacteriostatic water into your syringe
Inject slowly down the inside wall of the tirzepatide vial — not onto the powder
Swirl gently until completely clear and dissolved — never shake
Label with today's date — discard after 28 days
Refrigerate immediately at 2–8°C — do not freeze

Tirzepatide Reconstitution Calculator