Not medical adviceRetatrutide is investigational and not FDA-approved. Which diluent to use, sterile handling and storage are questions for a pharmacist. This page only explains the arithmetic.
How to reconstitute retatrutide: the math in three steps
- Concentration. Divide the milligrams in the vial by the millilitres of water you add. A 10 mg vial mixed with 2 mL gives 10 ÷ 2 = 5 mg/mL.
- Volume of the dose. Divide the dose by the concentration. For 2 mg: 2 ÷ 5 = 0.4 mL.
- Units on a U-100 syringe. Multiply millilitres by 100, because a U-100 insulin syringe holds 100 units per mL. 0.4 mL × 100 = 40 units.
The same dose always contains the same number of milligrams. Using more water spreads those milligrams through a larger volume, so you draw more units. Using less water concentrates them, so you draw fewer units. To check a measurement the other way round, use the units-to-mg converter.
Choosing a water volume
There is no single correct amount of water. It is a trade-off between two practical limits:
- Too little water makes the solution so concentrated that small doses become a couple of units or less. At that size, the thickness of a line on the syringe is a large share of the dose.
- Too much water makes larger doses exceed the syringe. A 0.3 mL syringe only holds 30 units, and a 1 mL syringe holds 100.
Many people choose a volume that makes the arithmetic round. For example, 1 mL of water per 10 mg gives 10 mg/mL, so 10 units = 1 mg. Half that strength (5 mg/mL) gives 20 units = 1 mg. The doses in the tables below are the steps used in clinical trials, listed in the retatrutide dosage chart.
| Vial | Water for 10 mg/mL (10 units = 1 mg) | Water for 5 mg/mL (20 units = 1 mg) |
|---|---|---|
| 5 mg | 0.5 mL | 1 mL |
| 10 mg | 1 mL | 2 mL |
| 15 mg | 1.5 mL | 3 mL |
| 20 mg | 2 mL | 4 mL |
| 24 mg | 2.4 mL | 4.8 mL |
| 30 mg | 3 mL | 6 mL |
How much bac water for 5mg retatrutide?
A retatrutide 5mg vial holds 5 mg of powder, whatever volume of water is added. Round-number options for a 5 mg vial: 0.5 mL gives 10 mg/mL (10 units = 1 mg); 1 mL gives 5 mg/mL (20 units = 1 mg). With 1 mL the vial holds 5 mg/mL, so 2 mg is 0.4 mL, or 40 units. A 5 mg vial contains 5 doses of 1 mg, 2.5 doses of 2 mg, 1.3 doses of 4 mg, before the small loss in the needle.
| Dose | 0.5 mL | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL |
|---|---|---|---|---|---|---|
| 1 mg | 10 | 20 | 30 | 40 | 50 | 60 |
| 2 mg | 20 | 40 | 60 | 80 | 100 | 120 |
| 4 mg | 40 | 80 | 120 | 160 | 200 | 240 |
How much bac water for 10mg retatrutide?
A retatrutide 10mg vial holds 10 mg of powder, whatever volume of water is added. Round-number options for a 10 mg vial: 1 mL gives 10 mg/mL (10 units = 1 mg); 2 mL gives 5 mg/mL (20 units = 1 mg). With 2 mL the vial holds 5 mg/mL, so 2 mg is 0.4 mL, or 40 units. A 10 mg vial contains 10 doses of 1 mg, 5 doses of 2 mg, 2.5 doses of 4 mg, before the small loss in the needle.
| Dose | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL |
|---|---|---|---|---|---|
| 1 mg | 10 | 15 | 20 | 25 | 30 |
| 2 mg | 20 | 30 | 40 | 50 | 60 |
| 4 mg | 40 | 60 | 80 | 100 | 120 |
| 6 mg | 60 | 90 | 120 | 150 | 180 |
| 8 mg | 80 | 120 | 160 | 200 | 240 |
| 9 mg | 90 | 135 | 180 | 225 | 270 |
How much bac water for 15mg retatrutide?
A retatrutide 15mg vial holds 15 mg of powder, whatever volume of water is added. Round-number options for a 15 mg vial: 1.5 mL gives 10 mg/mL (10 units = 1 mg); 3 mL gives 5 mg/mL (20 units = 1 mg). With 3 mL the vial holds 5 mg/mL, so 2 mg is 0.4 mL, or 40 units. A 15 mg vial contains 15 doses of 1 mg, 7.5 doses of 2 mg, 3.8 doses of 4 mg, before the small loss in the needle.
| Dose | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL |
|---|---|---|---|---|---|
| 1 mg | 6.7 | 10 | 13.3 | 16.7 | 20 |
| 2 mg | 13.3 | 20 | 26.7 | 33.3 | 40 |
| 4 mg | 26.7 | 40 | 53.3 | 66.7 | 80 |
| 6 mg | 40 | 60 | 80 | 100 | 120 |
| 8 mg | 53.3 | 80 | 106.7 | 133.3 | 160 |
| 9 mg | 60 | 90 | 120 | 150 | 180 |
| 12 mg | 80 | 120 | 160 | 200 | 240 |
How much bac water for 20mg retatrutide?
A retatrutide 20mg vial holds 20 mg of powder, whatever volume of water is added. Round-number options for a 20 mg vial: 2 mL gives 10 mg/mL (10 units = 1 mg); 4 mL gives 5 mg/mL (20 units = 1 mg). With 4 mL the vial holds 5 mg/mL, so 2 mg is 0.4 mL, or 40 units. A 20 mg vial contains 20 doses of 1 mg, 10 doses of 2 mg, 5 doses of 4 mg, before the small loss in the needle.
| Dose | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL | 4 mL |
|---|---|---|---|---|---|---|
| 1 mg | 5 | 7.5 | 10 | 12.5 | 15 | 20 |
| 2 mg | 10 | 15 | 20 | 25 | 30 | 40 |
| 4 mg | 20 | 30 | 40 | 50 | 60 | 80 |
| 6 mg | 30 | 45 | 60 | 75 | 90 | 120 |
| 8 mg | 40 | 60 | 80 | 100 | 120 | 160 |
| 9 mg | 45 | 67.5 | 90 | 112.5 | 135 | 180 |
| 12 mg | 60 | 90 | 120 | 150 | 180 | 240 |
How much bac water for 24mg retatrutide?
A retatrutide 24mg vial holds 24 mg of powder, whatever volume of water is added. Round-number options for a 24 mg vial: 2.4 mL gives 10 mg/mL (10 units = 1 mg); 4.8 mL gives 5 mg/mL (20 units = 1 mg). With 4.8 mL the vial holds 5 mg/mL, so 2 mg is 0.4 mL, or 40 units. A 24 mg vial contains 24 doses of 1 mg, 12 doses of 2 mg, 6 doses of 4 mg, before the small loss in the needle.
| Dose | 1 mL | 1.5 mL | 2 mL | 2.4 mL | 2.5 mL | 3 mL | 4.8 mL |
|---|---|---|---|---|---|---|---|
| 1 mg | 4.2 | 6.3 | 8.3 | 10 | 10.4 | 12.5 | 20 |
| 2 mg | 8.3 | 12.5 | 16.7 | 20 | 20.8 | 25 | 40 |
| 4 mg | 16.7 | 25 | 33.3 | 40 | 41.7 | 50 | 80 |
| 6 mg | 25 | 37.5 | 50 | 60 | 62.5 | 75 | 120 |
| 8 mg | 33.3 | 50 | 66.7 | 80 | 83.3 | 100 | 160 |
| 9 mg | 37.5 | 56.3 | 75 | 90 | 93.8 | 112.5 | 180 |
| 12 mg | 50 | 75 | 100 | 120 | 125 | 150 | 240 |
How much bac water for 30mg retatrutide?
A retatrutide 30mg vial holds 30 mg of powder, whatever volume of water is added. Round-number options for a 30 mg vial: 3 mL gives 10 mg/mL (10 units = 1 mg). With 6 mL the vial holds 5 mg/mL, so 2 mg is 0.4 mL, or 40 units. A 30 mg vial contains 30 doses of 1 mg, 15 doses of 2 mg, 7.5 doses of 4 mg, before the small loss in the needle.
| Dose | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL |
|---|---|---|---|---|---|
| 1 mg | 3.3 | 5 | 6.7 | 8.3 | 10 |
| 2 mg | 6.7 | 10 | 13.3 | 16.7 | 20 |
| 4 mg | 13.3 | 20 | 26.7 | 33.3 | 40 |
| 6 mg | 20 | 30 | 40 | 50 | 60 |
| 8 mg | 26.7 | 40 | 53.3 | 66.7 | 80 |
| 9 mg | 30 | 45 | 60 | 75 | 90 |
| 12 mg | 40 | 60 | 80 | 100 | 120 |
How many doses are in each vial size
Doses per vial is the vial's milligrams divided by the dose, and it does not depend on how much water you add. The table uses the phase 3 dose steps and ignores the small amount that stays in the needle and vial.
| Vial | 2 mg dose | 4 mg dose | 6 mg dose | 9 mg dose | 12 mg dose |
|---|---|---|---|---|---|
| 5 mg | 2.5 | 1.3 | 0.8 | 0.6 | 0.4 |
| 10 mg | 5 | 2.5 | 1.7 | 1.1 | 0.8 |
| 15 mg | 7.5 | 3.8 | 2.5 | 1.7 | 1.3 |
| 20 mg | 10 | 5 | 3.3 | 2.2 | 1.7 |
| 24 mg | 12 | 6 | 4 | 2.7 | 2 |
| 30 mg | 15 | 7.5 | 5 | 3.3 | 2.5 |
A value below 1 means a single dose needs more than one vial. The steps themselves come from the retatrutide dosing schedule used in trials.
Water needed for a target number of units
You can also work backwards: pick the number of units you want a dose to land on, and solve for the water volume. The formula is water (mL) = units × vial mg ÷ (dose mg × 100).
| Vial | Water to add | Resulting concentration |
|---|---|---|
| 5 mg | 0.5 mL | 10 mg/mL |
| 10 mg | 1 mL | 10 mg/mL |
| 15 mg | 1.5 mL | 10 mg/mL |
| 20 mg | 2 mL | 10 mg/mL |
| 24 mg | 2.4 mL | 10 mg/mL |
| 30 mg | 3 mL | 10 mg/mL |
Common measuring mistakes
- mg and mcg mixed up. 1 mg = 1,000 mcg. A 250 mcg dose is 0.25 mg, not 250 mg.
- Wrong syringe type. These numbers assume U-100 insulin syringes (100 units per mL). U-40 syringes hold 40 units per mL and give completely different readings.
- Counting from the wrong line. On a 1 mL syringe each small line is usually 2 units. On 0.3 mL and 0.5 mL syringes each line is usually 1 unit.
- Writing down the wrong water volume. If you are not sure how much water went into the vial, the concentration is unknown and no calculator can fix that.
For the safety background on products sold online as "research use only", read what the FDA says.
Related
- Retatrutide dosage calculatormg to units for any vial
- Dose in units and mLConversion charts and a reverse calculator
- Retatrutide dosage chartTrial escalation schedules
Frequently asked questions
Does adding more water make the dose weaker?
No. A 2 mg dose is 2 mg whatever the dilution. More water only means the 2 mg is in a larger volume, so you draw more units to get it.
How much bacteriostatic water for a 10 mg retatrutide vial?
It is a choice, not a fixed rule. 1 mL gives 10 mg/mL (10 units = 1 mg), and 2 mL gives 5 mg/mL (20 units = 1 mg). The full chart is in the 10 mg section.
How many doses are in a retatrutide 20mg vial?
It is simple division: 20 mg holds ten 2 mg doses, five 4 mg doses, or about 2.2 doses of 9 mg, before the small amount lost in the needle. Mixed with 2 mL of water it is 10 mg/mL, so 2 mg is 20 units. See the 20mg section.
How much bac water for 24 mg of retatrutide?
2.4 mL gives 10 mg/mL (10 units = 1 mg), and 4.8 mL gives 5 mg/mL. See the 24 mg section for units per dose.
How many units is 2 mg of retatrutide?
It depends on the concentration. At 5 mg/mL it is 40 units. At 10 mg/mL it is 20 units. Use the calculator above with your own vial and water amounts.
How long does reconstituted retatrutide last?
Retatrutide is not an approved medicine, so there is no official labeling on storage or stability after mixing. Ask a pharmacist. Do not rely on seller claims.