Tirzepatide dosage & BAC water calculator

How the tirzepatide calculation works

Tirzepatide doses are often discussed in milligrams, while many vials and syringes require you to think in mg, mcg, mL, and units at the same time.

The calculator normalizes everything into concentration first, then returns a draw volume and matching syringe-unit result.

• 10 mg equals 10,000 mcg
• 10,000 mcg / 2 mL = 5,000 mcg per mL
• 2,500 mcg / 5,000 mcg per mL = 0.5 mL

Tirzepatide 5 mg vial examples

A 5 mg vial in 2 mL gives 2.5 mg/mL (2,500 mcg/mL). A 2.5 mg dose is a full 1.0 mL — 100 units, the whole length of a 1 mL U-100 syringe.

To shrink that draw, use less water: 5 mg in 1 mL gives 5 mg/mL, so a 2.5 mg dose drops to 0.5 mL (50 units). A starter dose of 1.25 mg at 2.5 mg/mL is 0.5 mL (50 units).

• 5 mg / 2 mL = 2.5 mg/mL → 2.5 mg = 1.0 mL = 100 units
• 5 mg / 1 mL = 5 mg/mL → 2.5 mg = 0.5 mL = 50 units
• A 5 mg vial holds about two 2.5 mg doses

Tirzepatide 10 mg vial with 2 mL example

A 10 mg tirzepatide vial mixed with 2 mL gives 5 mg/mL, or 5,000 mcg/mL.

A 2.5 mg target dose is 2,500 mcg. At 5 mg/mL, that is 0.5 mL, which equals 50 units on a U-100 syringe.

• 10 mg / 2 mL = 5 mg/mL
• 2.5 mg = 2,500 mcg
• 2,500 mcg / 5,000 mcg per mL = 0.5 mL = 50 U-100 units

Tirzepatide 15 mg vial with 3 mL example

A 15 mg tirzepatide vial mixed with 3 mL also gives 5 mg/mL, or 5,000 mcg/mL.

Because the concentration is the same as the 10 mg with 2 mL example, a 2.5 mg dose is still 0.5 mL, or 50 U-100 units.

• 15 mg / 3 mL = 5 mg/mL
• 2.5 mg / 5 mg per mL = 0.5 mL
• 0.5 mL x 100 = 50 U-100 units

How much BAC water for a 20 mg tirzepatide vial

A 20 mg vial in 2 mL gives 10 mg/mL. A 2.5 mg dose is 0.25 mL (25 units), 5 mg is 0.5 mL (50 units), and 10 mg is a full 1.0 mL (100 units), so every step up to 10 mg fits a 1 mL syringe.

In 4 mL the vial is 5 mg/mL — the same concentration as 10 mg in 2 mL — and every draw doubles: 2.5 mg = 50 units, 5 mg = 100 units. A 20 mg vial holds about eight 2.5 mg doses or four 5 mg doses.

• 20 mg / 2 mL = 10 mg/mL → 2.5 mg = 25 units, 5 mg = 50 units, 10 mg = 100 units
• 20 mg / 4 mL = 5 mg/mL → 2.5 mg = 50 units, 5 mg = 100 units
• About eight 2.5 mg doses or four 5 mg doses per vial

How much BAC water for a 30 mg tirzepatide vial

A 30 mg vial in 3 mL gives 10 mg/mL (10,000 mcg/mL). A 2.5 mg dose is 0.25 mL, which is 25 units on a U-100 syringe.

Because the vial is so concentrated, larger maintenance doses stay easy to draw: 5 mg is 0.5 mL (50 units) and 10 mg is a full 1.0 mL (100 units). Above 10 mg you would exceed a standard 1 mL syringe, so add more water if you dose that high.

• 30 mg / 3 mL = 10 mg/mL → 2.5 mg = 0.25 mL = 25 units
• 30 mg / 3 mL = 10 mg/mL → 5 mg = 0.5 mL = 50 units
• 30 mg / 6 mL = 5 mg/mL → 2.5 mg = 0.5 mL = 50 units (easier early-titration draws)

How much BAC water for a 40 mg tirzepatide vial

A 40 mg vial in 4 mL gives 10 mg/mL. A 2.5 mg dose is 0.25 mL (25 units); a 5 mg dose is 0.5 mL (50 units); a 10 mg dose is a full 1.0 mL (100 units).

At 10 mg/mL any dose above 10 mg is more than 1 mL and will not fit a standard insulin syringe, so add more water to lower the concentration and re-run the math if you dose that high.

• 40 mg / 4 mL = 10 mg/mL → 2.5 mg = 0.25 mL = 25 units
• 40 mg / 4 mL = 10 mg/mL → 5 mg = 0.5 mL = 50 units
• A 40 mg vial yields about sixteen 2.5 mg doses

How much BAC water for a 60 mg tirzepatide vial

A 60 mg vial in 3 mL gives 20 mg/mL. The draws get small: 2.5 mg is 0.125 mL (12.5 units), 5 mg is 0.25 mL (25 units), 10 mg is 0.5 mL (50 units) and 15 mg is 0.75 mL (75 units).

In 6 mL the vial is 10 mg/mL and every draw doubles (2.5 mg = 25 units, 5 mg = 50 units), which is easier to read for early titration steps. Check that the vial can physically hold 6 mL before adding it. At 5 mg per dose a 60 mg vial holds about twelve doses, so confirm the reconstituted beyond-use date covers the whole vial.

• 60 mg / 3 mL = 20 mg/mL → 2.5 mg = 12.5 units, 5 mg = 25 units, 15 mg = 75 units
• 60 mg / 6 mL = 10 mg/mL → 2.5 mg = 25 units, 5 mg = 50 units, 10 mg = 100 units
• About twenty-four 2.5 mg doses or twelve 5 mg doses per vial

How much BAC water for a 100 mg tirzepatide vial

A 100 mg vial in 5 mL gives 20 mg/mL — the same concentration as 60 mg in 3 mL — so the units are identical: 2.5 mg = 12.5 units, 5 mg = 25 units, 10 mg = 50 units. In 10 mL it is 10 mg/mL and every draw doubles.

A 100 mg vial holds about twenty 5 mg doses, which at one dose a week is longer than most reconstituted beyond-use windows. Check the date your pharmacy or label gives before mixing the whole vial, and confirm the vial's fill capacity before choosing a large water volume.

• 100 mg / 5 mL = 20 mg/mL → 2.5 mg = 12.5 units, 5 mg = 25 units, 10 mg = 50 units
• 100 mg / 10 mL = 10 mg/mL → 2.5 mg = 25 units, 5 mg = 50 units
• Plan around the beyond-use date, not just the dose count

How much BAC water for tirzepatide?

Bacteriostatic water volume sets your concentration, so it directly changes the syringe units you draw. There is no single correct amount — choose a volume that puts your target dose at an easy-to-read number of units on a U-100 syringe.

For a 10 mg vial: 1 mL gives 10 mg/mL (a 2.5 mg dose = 0.25 mL = 25 units), 2 mL gives 5 mg/mL (2.5 mg = 0.5 mL = 50 units), and 3 mL gives about 3.33 mg/mL (2.5 mg = 0.75 mL = 75 units).

• More BAC water = lower concentration = more units for the same dose
• 10 mg / 1 mL = 10 mg/mL; 10 mg / 2 mL = 5 mg/mL; 10 mg / 3 mL = 3.33 mg/mL
• Aim for a draw that lands on clear unit markings to reduce dosing error

Tirzepatide dose-to-units chart (10 mg vial in 2 mL)

Once a 10 mg vial is reconstituted in 2 mL (5 mg/mL), the standard titration steps map to fixed unit draws, so you can read your weekly dose straight off the syringe. Every 1 mg of dose is 0.2 mL, which is 20 units at this concentration.

This chart assumes the 5 mg/mL setup only. If you use a different vial size or water volume, the units change — enter your own numbers in the calculator above to regenerate them.

• 2.5 mg = 0.5 mL = 50 units
• 5 mg = 1.0 mL = 100 units (a full 1 mL U-100 syringe)
• 7.5 mg = 1.5 mL = 150 units (needs two draws on a 1 mL syringe)
• 10 mg = 2.0 mL = 200 units
• 12.5 mg = 2.5 mL = 250 units

Tirzepatide doses in units by concentration

The number of units for a tirzepatide dose depends only on the concentration in the vial. For a vial you mix yourself, that is the vial's mg divided by the mL of water you add, so 10 mg in 2 mL is 5 mg/mL. Compounded vials often arrive already mixed with the strength printed on the label, and there is no standard: pharmacy products include 8, 17 and 20 mg/mL, so the same 2.5 mg dose can be anywhere from 12.5 to 31 units.

The rows use the dose steps on the Zepbound and Mounjaro labels, which start at 2.5 mg a week and go up in 2.5 mg steps after at least four weeks on each dose, to a maximum of 15 mg. A compounded prescription may use different steps, so use the dose your prescriber wrote and the concentration on your own label.

• 2.5 mg at 5 mg/mL = 0.5 mL = 50 units
• 2.5 mg at 10 mg/mL = 0.25 mL = 25 units
• 2.5 mg at 20 mg/mL = 0.125 mL = 12.5 units

See also: Tirzepatide dosage chart (weekly schedule)

How many mg is 40 units of tirzepatide?

When your instructions are written in units, read the maths the other way round: units ÷ 100 gives mL on a U-100 syringe, and mL × the concentration gives mg. 40 units is 0.4 mL, which is 4 mg at 10 mg/mL, 6.8 mg at 17 mg/mL and 8 mg at 20 mg/mL.

The same mark on the syringe is a different dose at every strength. The FDA has warned about compounded semaglutide dosing errors in which patients drew 5 to 20 times the intended dose after mixing up units and mL, and the same mix-up can happen with any premixed GLP-1 vial, so check the mg/mL on your label every time a new vial arrives.

• mg = units ÷ 100 × mg/mL
• 40 units at 10 mg/mL = 4 mg
• 40 units at 20 mg/mL = 8 mg

When to re-check the math

Recalculate when you change vial size, BAC water volume, dose, syringe type, or syringe capacity. Saving the setup in PepSync helps avoid re-entering the same details each week.