Last updated: June 2026 · Reviewed June 2026 · Built by the InjectBuddy team
How many units is 2 mg retatrutide? U-100 draw guide by vial and water fill
A 2 mg retatrutide dose is 20 units on a U-100 syringe at 10 mg/mL, and 40 units at half that strength (5 mg/mL). There is no fixed unit count for "2 mg" until you fix two numbers — total mg in the vial and mL of bacteriostatic (BAC) water added — because those set the concentration, and concentration sets the draw. This guide explains the three-step formula, works through seven examples across 10 mg, 15 mg, and 20 mg vials, and answers the questions people ask most.
- Units = (dose mg ÷ concentration mg/mL) × 100. For 2 mg at 10 mg/mL that is (2 ÷ 10) × 100 = 20 units.
- Same dose, different vial/water = different units. A 10 mg vial in 1 mL and a 20 mg vial in 2 mL are both 10 mg/mL, so both read 20 units for 2 mg.
- Retatrutide is investigational — no licensed human dose exists. The 2 mg figure is a trial escalation step, used only to anchor the arithmetic.
Where the 2 mg figure comes from
2 mg is not a recommended dose — it is an early escalation step in the phase 2 obesity trial, where participants on higher targets started at 2 mg or 4 mg and titrated up; the 2 mg start had fewer gastrointestinal events than a 4 mg start (Jastreboff et al., NEJM 2023). Retatrutide is a triple agonist at the GIP, GLP-1 and glucagon receptors, still in trials across obesity, type 2 diabetes (Rosenstock et al., Lancet 2023) and steatotic liver disease (Sanyal et al., Nat Med 2024). It is not FDA-approved, and no human dose is established outside those supervised settings (Kaur & Misra, Eur J Clin Pharmacol 2024). This page is a measurement reference, not medical advice.
The unit marks on a U-100 insulin syringe count hundredths of a milliliter: 100 units = 1 mL, so 1 unit = 0.01 mL. To turn any milligram dose into units you first find how many milliliters of solution hold that dose, then multiply by 100.
How this is calculated
Three steps take you from a dry vial to a unit count, and they hold for any reconstituted peptide:
- Concentration (mg/mL) = total mg in vial ÷ mL of BAC water added.
- Volume for the dose (mL) = dose mg ÷ concentration mg/mL.
- Units (U-100) = volume mL × 100.
If the milligram-to-milliliter relationship is unfamiliar, how mg/mL works and U-100 syringe units explained cover the underlying conversions.
10 mg vial, 1 mL BAC water. Concentration = 10 ÷ 1 = 10 mg/mL. Volume for 2 mg = 2 ÷ 10 = 0.20 mL. Units = 0.20 × 100 = 20 units.
10 mg vial, 2 mL BAC water. Concentration = 10 ÷ 2 = 5 mg/mL. Volume for 2 mg = 2 ÷ 5 = 0.40 mL. Units = 0.40 × 100 = 40 units — double, because the solution is half as strong.
2 mg dose chart by vial size and BAC water fill
Retatrutide vials are commonly 10 mg, 15 mg or 20 mg of lyophilised powder. The table gives the units for a 2 mg dose at three common BAC water fills on a U-100 syringe, rounded to one decimal place.
| Vial size | BAC water | Concentration | Volume for 2 mg | Units (U-100) |
|---|---|---|---|---|
| 10 mg | 1 mL | 10 mg/mL | 0.20 mL | 20 |
| 10 mg | 2 mL | 5 mg/mL | 0.40 mL | 40 |
| 10 mg | 3 mL | 3.33 mg/mL | 0.60 mL | 60 |
| 15 mg | 1 mL | 15 mg/mL | 0.13 mL | 13.3 |
| 15 mg | 2 mL | 7.5 mg/mL | 0.27 mL | 26.7 |
| 15 mg | 3 mL | 5 mg/mL | 0.40 mL | 40 |
| 20 mg | 1 mL | 20 mg/mL | 0.10 mL | 10 |
| 20 mg | 2 mL | 10 mg/mL | 0.20 mL | 20 |
| 20 mg | 3 mL | 6.67 mg/mL | 0.30 mL | 30 |
2 mg lands on the same 20-unit mark from a 10 mg vial in 1 mL and a 20 mg vial in 2 mL: both are 10 mg/mL. Concentration is what matters, not the vial label — the principle covered in why water amount changes syringe units.
20 mg vial, 1 mL BAC water. Concentration = 20 ÷ 1 = 20 mg/mL. Volume for 2 mg = 2 ÷ 20 = 0.10 mL. Units = 0.10 × 100 = 10 units — the smallest reliable draw of the set, easy to under-measure if the syringe prints in 2-unit steps.
15 mg vial, 1 mL BAC water. Concentration = 15 ÷ 1 = 15 mg/mL. Volume for 2 mg = 2 ÷ 15 = 0.133 mL. Units = 0.133 × 100 = 13.3 units — an awkward landing point between marks, which is exactly the kind of fill to avoid.
Choosing a fill that keeps the draw readable
A fill that puts 2 mg at an awkward fraction of a unit is harder to measure. Whole or half-unit landing points are easier to hit on a U-100 syringe, and keep later titration steps tidy too.
15 mg vial, choose 3 mL so 2 mg reads round. Concentration = 15 ÷ 3 = 5 mg/mL. Volume for 2 mg = 2 ÷ 5 = 0.40 mL = 40 units. The same 3 mL fill keeps a later 4 mg step at a clean 80 units.
10 mg vial at 2 mL (5 mg/mL) as a titration ladder: 2 mg = 40 units, 4 mg = 0.80 mL = 80 units, and 6 mg = 1.20 mL = 120 units, which exceeds a single 100-unit barrel and would need a larger syringe or two draws.
The how much BAC water should I add guide covers the concentration-versus-volume trade-off in depth.
Reading the result on your syringe
Confirm three things before trusting the number: the syringe is U-100 (not U-40 or U-50, which use different scales), the marks are single units not 2-unit increments, and the total volume fits the barrel. If your syringe prints in 2-unit steps, an odd result such as 13.3 cannot be set precisely — another reason to pick a fill that lands on a clean mark.
Sanity-check by reversing the maths: you drew 30 units from a 20 mg vial in 3 mL. Concentration = 20 ÷ 3 = 6.67 mg/mL. Volume = 30 ÷ 100 = 0.30 mL. Dose = 0.30 × 6.67 = 2.0 mg. The reverse calculation matching your target is the fastest error catch.
Honest caveat: this is arithmetic, not a protocol
Because retatrutide is investigational, there is no approved label, no established human dose, and no quality-assured supply behind non-trial vials — their potency and sterility are unverified. The maths above tells you how many units correspond to a stated milligram amount at a stated concentration; it does not tell you any amount is safe for you. Treat this page as a units converter and take dosing decisions to a qualified clinician.
So, how many units is 2mg retatrutide?
It depends entirely on the concentration you create when you reconstitute the vial. At 10 mg/mL (for example, a 10 mg vial in 1 mL of BAC water), 2 mg is 20 units; at 5 mg/mL (10 mg in 2 mL) the same dose is 40 units. The formula is always: units = (dose mg divided by concentration mg/mL) multiplied by 100. Use the retatrutide calculator to enter your own vial size and water volume and get the exact unit mark in one step.
FAQs
2 mg retatrutide is how many units?
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Sources
- Jastreboff AM, Kaplan LM, Frias JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. pubmed.ncbi.nlm.nih.gov/37366315.
- Rosenstock J, Frias J, Jastreboff AM, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised phase 2 trial. Lancet. 2023;402(10401):529-544. pubmed.ncbi.nlm.nih.gov/37385280.
- Sanyal AJ, Kaplan LM, Frias JP, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med. 2024;30(7):2037-2048. pmc.ncbi.nlm.nih.gov/articles/PMC11271400.
- Kaur M, Misra S. A review of an investigational drug retatrutide, a novel triple agonist agent for the treatment of obesity. Eur J Clin Pharmacol. 2024;80(5):669-676. pubmed.ncbi.nlm.nih.gov/38367045.
- Johnson JL, Downes JM, Obi CK, Asante NB. Novel Concentrated Insulin Delivery Devices: Developments for Safe and Simple Dose Conversions. J Diabetes Sci Technol. 2017;11(3):618-622. pmc.ncbi.nlm.nih.gov/articles/PMC5505430.
InjectBuddy is a maths tool, not a medical service. Retatrutide is an investigational compound with no established human dose; this guide is for general educational purposes only and does not constitute medical advice. Always follow a qualified prescriber's instructions.