How much bacteriostatic water to reconstitute 10 mg retatrutide?

The water volume only sets the concentration; any volume works mathematically. 10 mg in 2 mL gives 5 mg/mL (2 mg = 40 units); in 1 mL it gives 10 mg/mL (2 mg = 20 units). Larger volumes give larger, easier-to-read unit counts. This is arithmetic, not a preparation instruction.

Are FDA-approved pens and vials reconstituted?

No. Zepbound, Mounjaro, Wegovy and Ozempic are supplied as ready-to-use solutions. Reconstitution math applies to lyophilized (freeze-dried) vials, which for these molecules are compounded or research products that the FDA has not approved.

How do I choose the water volume for a target unit mark?

Rearrange the formula: water mL = vial mg × target units ÷ (dose mg × 100). For a 10 mg vial and a 2.5 mg amount that should read 25 units, water = 10 × 25 ÷ 250 = 1 mL.

Does more water change the amount of drug?

No. The vial mg is fixed; water only spreads it over more volume. Doubling the water halves the concentration and doubles the units needed for the same mg.

Is retatrutide FDA approved?

No. As of Oct 19, 2026 retatrutide is investigational. Lilly reported Phase 3 results in 2026 and said it plans to submit to the FDA in the first quarter of 2027. It is legally available only to participants in Lilly clinical trials.

Retatrutide Reconstitution Calculator & Chart

Short answer

Concentration = vial mg ÷ water mL; units = dose mg ÷ concentration × 100. Example: 10 mg + 2 mL = 5 mg/mL, so 2.5 mg = 50 units. For a target mark, water mL = vial mg × target units ÷ (dose mg × 100). Arithmetic as of Oct 19, 2026; not dosing advice.

Units on U-100: 40 U (raw 40)
Volume: 0.4 mL
Concentration: 5 mg/mL
Draws per vial: 5
Water for target mark: 2.5 mL

Lands exactly on a printed mark: 40 U.

1 unit = 0.05 mg · 10 units = 0.5 mg at 5 mg/mL.

Drag the plunger, or focus the diagram and use the arrow keys, to set the amount by syringe mark.

Water volumes that put 2 mg exactly on a printed mark of this syringe:

U-100 scale: 100 units = 1 mL, so 1 unit = 0.01 mL. Units round to the nearest 0.5 U.

10 mg ÷ 2 mL = 5 mg/mL. 2 mg ÷ 5 mg/mL = 0.4 mL × 100 = 40 U.

Math, parameters and sources: model card.

From vial to syringe: the default example (10 mg vial, 2 mL water, 2 mg) in three steps

Vial and water
10 mg + 2 mL
The mg in the vial never changes; water only sets how spread out it is.
Concentration
10 ÷ 2 = 5 mg/mL
Milligrams in every milliliter of solution.
Units on a U-100 syringe
2 mg ÷ 5 = 0.4 mL = 40 U
100 units = 1 mL, so units = mL × 100 (rounded to 0.5 U).

Vial × water chart

Pre-calculated U-100 readings for common vial sizes and water volumes. Every cell uses the same formula as the calculator. Retatrutide is investigational; these are arithmetic tables, not preparation or administration instructions.

5 mg vial: U-100 units to draw for each dose (1 mL = 5 mg/mL; 2 mL = 2.5 mg/mL; 3 mL = 1.667 mg/mL)
Dose	1 mL water5 mg/mL	2 mL water2.5 mg/mL	3 mL water1.667 mg/mL
0.25 mg	5 U	10 U	15 U
0.5 mg	10 U	20 U	30 U
1 mg	20 U	40 U	60 U
2 mg	40 U	80 U	—
2.5 mg	50 U	100 U	—
4 mg	80 U	—	—
5 mg	100 U	—	—
6 mg	—	—	—
8 mg	—	—	—
9 mg	—	—	—
10 mg	—	—	—
12 mg	—	—	—

10 mg vial: U-100 units to draw for each dose (1 mL = 10 mg/mL; 2 mL = 5 mg/mL; 3 mL = 3.333 mg/mL)
Dose	1 mL water10 mg/mL	2 mL water5 mg/mL	3 mL water3.333 mg/mL
0.25 mg	2.5 U	5 U	7.5 U
0.5 mg	5 U	10 U	15 U
1 mg	10 U	20 U	30 U
2 mg	20 U	40 U	60 U
2.5 mg	25 U	50 U	75 U
4 mg	40 U	80 U	—
5 mg	50 U	100 U	—
6 mg	60 U	—	—
8 mg	80 U	—	—
9 mg	90 U	—	—
10 mg	100 U	—	—
12 mg	—	—	—

15 mg vial: U-100 units to draw for each dose (1 mL = 15 mg/mL; 2 mL = 7.5 mg/mL; 3 mL = 5 mg/mL)
Dose	1 mL water15 mg/mL	2 mL water7.5 mg/mL	3 mL water5 mg/mL
0.25 mg	1.5 U (raw 1.67)	3.5 U (raw 3.33)	5 U
0.5 mg	3.5 U (raw 3.33)	6.5 U (raw 6.67)	10 U
1 mg	6.5 U (raw 6.67)	13.5 U (raw 13.33)	20 U
2 mg	13.5 U (raw 13.33)	26.5 U (raw 26.67)	40 U
2.5 mg	16.5 U (raw 16.67)	33.5 U (raw 33.33)	50 U
4 mg	26.5 U (raw 26.67)	53.5 U (raw 53.33)	80 U
5 mg	33.5 U (raw 33.33)	66.5 U (raw 66.67)	100 U
6 mg	40 U	80 U	—
8 mg	53.5 U (raw 53.33)	—	—
9 mg	60 U	—	—
10 mg	66.5 U (raw 66.67)	—	—
12 mg	80 U	—	—

20 mg vial: U-100 units to draw for each dose (1 mL = 20 mg/mL; 2 mL = 10 mg/mL; 3 mL = 6.667 mg/mL)
Dose	1 mL water20 mg/mL	2 mL water10 mg/mL	3 mL water6.667 mg/mL
0.25 mg	1.5 U (raw 1.25)	2.5 U	4 U (raw 3.75)
0.5 mg	2.5 U	5 U	7.5 U
1 mg	5 U	10 U	15 U
2 mg	10 U	20 U	30 U
2.5 mg	12.5 U	25 U	37.5 U
4 mg	20 U	40 U	60 U
5 mg	25 U	50 U	75 U
6 mg	30 U	60 U	90 U
8 mg	40 U	80 U	—
9 mg	45 U	90 U	—
10 mg	50 U	100 U	—
12 mg	60 U	—	—

30 mg vial: U-100 units to draw for each dose (1 mL = 30 mg/mL; 2 mL = 15 mg/mL; 3 mL = 10 mg/mL)
Dose	1 mL water30 mg/mL	2 mL water15 mg/mL	3 mL water10 mg/mL
0.25 mg	1 U (raw 0.83)	1.5 U (raw 1.67)	2.5 U
0.5 mg	1.5 U (raw 1.67)	3.5 U (raw 3.33)	5 U
1 mg	3.5 U (raw 3.33)	6.5 U (raw 6.67)	10 U
2 mg	6.5 U (raw 6.67)	13.5 U (raw 13.33)	20 U
2.5 mg	8.5 U (raw 8.33)	16.5 U (raw 16.67)	25 U
4 mg	13.5 U (raw 13.33)	26.5 U (raw 26.67)	40 U
5 mg	16.5 U (raw 16.67)	33.5 U (raw 33.33)	50 U
6 mg	20 U	40 U	60 U
8 mg	26.5 U (raw 26.67)	53.5 U (raw 53.33)	80 U
9 mg	30 U	60 U	90 U
10 mg	33.5 U (raw 33.33)	66.5 U (raw 66.67)	100 U
12 mg	40 U	80 U	—

40 mg vial: U-100 units to draw for each dose (1 mL = 40 mg/mL; 2 mL = 20 mg/mL; 3 mL = 13.333 mg/mL)
Dose	1 mL water40 mg/mL	2 mL water20 mg/mL	3 mL water13.333 mg/mL
0.25 mg	0.5 U (raw 0.63)	1.5 U (raw 1.25)	2 U (raw 1.88)
0.5 mg	1.5 U (raw 1.25)	2.5 U	4 U (raw 3.75)
1 mg	2.5 U	5 U	7.5 U
2 mg	5 U	10 U	15 U
2.5 mg	6.5 U (raw 6.25)	12.5 U	19 U (raw 18.75)
4 mg	10 U	20 U	30 U
5 mg	12.5 U	25 U	37.5 U
6 mg	15 U	30 U	45 U
8 mg	20 U	40 U	60 U
9 mg	22.5 U	45 U	67.5 U
10 mg	25 U	50 U	75 U
12 mg	30 U	60 U	90 U

60 mg vial: U-100 units to draw for each dose (1 mL = 60 mg/mL; 2 mL = 30 mg/mL; 3 mL = 20 mg/mL)
Dose	1 mL water60 mg/mL	2 mL water30 mg/mL	3 mL water20 mg/mL
0.25 mg	0.5 U (raw 0.42)	1 U (raw 0.83)	1.5 U (raw 1.25)
0.5 mg	1 U (raw 0.83)	1.5 U (raw 1.67)	2.5 U
1 mg	1.5 U (raw 1.67)	3.5 U (raw 3.33)	5 U
2 mg	3.5 U (raw 3.33)	6.5 U (raw 6.67)	10 U
2.5 mg	4 U (raw 4.17)	8.5 U (raw 8.33)	12.5 U
4 mg	6.5 U (raw 6.67)	13.5 U (raw 13.33)	20 U
5 mg	8.5 U (raw 8.33)	16.5 U (raw 16.67)	25 U
6 mg	10 U	20 U	30 U
8 mg	13.5 U (raw 13.33)	26.5 U (raw 26.67)	40 U
9 mg	15 U	30 U	45 U
10 mg	16.5 U (raw 16.67)	33.5 U (raw 33.33)	50 U
12 mg	20 U	40 U	60 U

Units = dose mg ÷ (vial mg ÷ water mL) × 100, rounded to the nearest 0.5 U; the raw value is shown in brackets when rounding changed it. A dash means the draw would exceed a 100-unit syringe or the vial. Arithmetic only; not dosing advice.

Rounding, syringe size and dead space

Results round to the nearest 0.5 unit because U-100 syringes are marked in 1-unit (30 and 50 U) or 2-unit (100 U) steps; the raw value is always shown next to the rounded one. The calculator warns when a draw exceeds the chosen syringe or falls under 2 units, where a half-unit reading error is 25% or more of the amount. Dead space (liquid held in the hub and needle) does not change the units for one draw, but it lowers how many draws a vial yields.

Frequently asked questions

How much bacteriostatic water to reconstitute 10 mg retatrutide?: The water volume only sets the concentration; any volume works mathematically. 10 mg in 2 mL gives 5 mg/mL (2 mg = 40 units); in 1 mL it gives 10 mg/mL (2 mg = 20 units). Larger volumes give larger, easier-to-read unit counts. This is arithmetic, not a preparation instruction.
Are FDA-approved pens and vials reconstituted?: No. Zepbound, Mounjaro, Wegovy and Ozempic are supplied as ready-to-use solutions. Reconstitution math applies to lyophilized (freeze-dried) vials, which for these molecules are compounded or research products that the FDA has not approved.
How do I choose the water volume for a target unit mark?: Rearrange the formula: water mL = vial mg × target units ÷ (dose mg × 100). For a 10 mg vial and a 2.5 mg amount that should read 25 units, water = 10 × 25 ÷ 250 = 1 mL.
Does more water change the amount of drug?: No. The vial mg is fixed; water only spreads it over more volume. Doubling the water halves the concentration and doubles the units needed for the same mg.
Is retatrutide FDA approved?: No. As of Oct 19, 2026 retatrutide is investigational. Lilly reported Phase 3 results in 2026 and said it plans to submit to the FDA in the first quarter of 2027. It is legally available only to participants in Lilly clinical trials.

Sources

Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial. Eli Lilly and Company (via PR Newswire; also investor.lilly.com), May 21, 2026. Accessed Oct 19, 2026.
Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. N Engl J Med (abstract via PubMed PMID 42814954; doi:10.1056/NEJMoa2604169), Sep 29, 2026. Accessed Oct 19, 2026.
LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial. The Lancet 2022;400(10366):1869-1881 (abstract via PubMed PMID 36354040; doi:10.1016/S0140-6736(22)02033-5), Oct 27, 2022. Accessed Oct 19, 2026.
Study Protocol J1I-MC-GZBF(b) for NCT04881760 (Prot_000.pdf). Eli Lilly and Company, hosted on ClinicalTrials.gov, Aug 29, 2022. Accessed Oct 19, 2026.
Warning Letter: Peak Performance Peptides, MARCS-CMS 735127. U.S. Food and Drug Administration, Aug 24, 2026. Accessed Oct 19, 2026.

Printed from GLP Ladder. To recreate this result, open https://glpladder.com/tools/retatrutide-reconstitution/

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