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Retatrutide reconstitution calculator

Pre-filled with an illustrative 10 mg vial and 2 mL of bacteriostatic water. Tweak any input — the math updates instantly.

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Concentration

5.00 mg/mL

Draw (units)

40.0

Draw (mL)

0.400

Doses / vial

5

Retatrutide is an experimental once-a-week injection people are tracking for weight loss and blood-sugar effects. It's the first triple agonist — it hits GLP-1, GIP, and glucagon receptors together, which appears to amplify both appetite suppression and energy expenditure. In a Phase 2 trial, adults with obesity lost about 24.2% of body weight at 48 weeks on the highest dose. It is still investigational and not approved. This page covers the reconstitution math and weekly logging cadence. The calculator above is pre-filled so you can see how the math plays out for a typical Retatrutide vial.

How the Retatrutide reconstitution calculator works

A 10 mg retatrutide vial mixed with 2 mL water gives 5 mg/mL — the same concentration as a 10 mg tirzepatide vial. The 2 mg illustrative dose drawn from that vial is exactly 40 units on a U-100 syringe. Repeatable across weeks, and easy to verify before each draw.

In the worked example below, a 10 mg vial of Retatrutide reconstituted with 2 mL of BAC water produces a concentration of 5 mg/mL. To draw the example dose of 2 mg from that vial you pull 0.40 mL — about 40 units on a standard insulin syringe. Change any input and the rest updates instantly so you can pre-plan a vial before you ever touch a needle.

Vial size, diluent volume, and dose are the three inputs that genuinely change the answer. Doses-per-vial is a derived output — it's the vial mg divided by the dose mg, rounded down. The most common edge case is a tiny dose: at very high concentration, a 0.1 mL draw is only a few units on the syringe, which is hard to read accurately. If your unit count drops below five, consider reconstituting the next vial with more BAC water so each dose covers a larger volume.

The illustrative example on this page assumes a 10 mg vial reconstituted with 2 mL of bacteriostatic water. That produces a concentration of 5 mg per mL, which makes a 2 mg illustrative dose exactly 0.4 mL — 40 units on a U-100 syringe.

Larger vials of retatrutide benefit from larger diluent volumes for the same reason any peptide does: per-dose draws land on cleaner, easier-to-read unit counts on the syringe. A 20 mg vial reconstituted with 4 mL of bacteriostatic water gives the same per-dose unit count as a 10 mg vial with 2 mL, just over twice as many total doses.

The larger dose magnitudes studied in retatrutide trials introduce practical considerations for reconstitution and administration volume. Higher doses, such as the 8 mg or 12 mg levels observed in trial publications, require careful planning to manage the volume drawn for injection. For instance, using a standard reconstitution of a 10 mg vial with 2 mL of bacteriostatic water results in a concentration of 5 mg/mL. At this concentration, drawing a 12 mg dose would require a volume of 2.4 mL. This volume exceeds the capacity of a standard 1 mL U-100 insulin syringe and would necessitate either multiple separate injections or the use of a larger syringe, such as a 3 mL syringe, for a single administration. Planning reconstitution concentration with the final target dose in mind is critical for managing injection logistics.

Worked example

A worked Retatrutide reconstitution, step by step

  1. Start with the vial: 10 mg of Retatrutide sitting in dry powder.
  2. Inject 2 mL of bacteriostatic water down the inside wall — don't shoot it straight at the powder.
  3. Concentration locks in at 10 ÷ 2 = 5.00 mg/mL for the entire life of the vial.
  4. A 2 mg dose becomes 0.400 mL of liquid, which reads as 40 units on a U-100 syringe.
  5. That vial has 5 clean draws in it before a partial dose at the bottom forces a new vial.

Retatrutide BAC water choices for this vial

The same 10 mg Retatrutide vial mixed with three different bacteriostatic water volumes. Doses-per-vial stays constant; the syringe unit count changes.

BAC water (mL)Concentration (mg/mL)Units for 2 mg dose
110.0020
25.0040
33.3360

Lower BAC water volume concentrates the Retatrutide solution and shrinks the unit count per dose. Higher volume spreads the dose into a more readable unit range.

Scenarios people actually run into

Three things that come up logging Retatrutide

  • Fresh 10 mg vial, no time to look things up. 2 mL of bacteriostatic water down the inside wall, swirl for a minute, write the date on the cap, done — concentration is now 5.00 mg/mL for the next 5-ish weeks.
  • Your previous vial was reconstituted differently. Don't trust muscle memory on the unit count — the new vial's concentration is the only number that drives this draw.
  • Powder didn't fully dissolve after the swirl. Wait the full five minutes before assuming anything is wrong; Retatrutide is slower to dissolve than the cleanest GLP-1s, and shaking the vial is the most common way to wreck a fresh reconstitution.

Same-category neighbor

Retatrutide next to Semaglutide

Both sit in the GLP-1 bucket — here's the reconstitution math side by side on each one's example vial.

RetatrutideSemaglutide
Vial10 mg5 mg
BAC water2 mL2 mL
Concentration5.00 mg/mL2.50 mg/mL

Want the full breakdown? Semaglutide reference →

Reconstitution notes for Retatrutide

The illustrative example on this page assumes a 10 mg vial reconstituted with 2 mL of bacteriostatic water. That produces a concentration of 5 mg per mL, which makes a 2 mg illustrative dose exactly 0.4 mL — 40 units on a U-100 syringe.

Larger vials of retatrutide benefit from larger diluent volumes for the same reason any peptide does: per-dose draws land on cleaner, easier-to-read unit counts on the syringe. A 20 mg vial reconstituted with 4 mL of bacteriostatic water gives the same per-dose unit count as a 10 mg vial with 2 mL, just over twice as many total doses.

The larger dose magnitudes studied in retatrutide trials introduce practical considerations for reconstitution and administration volume. Higher doses, such as the 8 mg or 12 mg levels observed in trial publications, require careful planning to manage the volume drawn for injection. For instance, using a standard reconstitution of a 10 mg vial with 2 mL of bacteriostatic water results in a concentration of 5 mg/mL. At this concentration, drawing a 12 mg dose would require a volume of 2.4 mL. This volume exceeds the capacity of a standard 1 mL U-100 insulin syringe and would necessitate either multiple separate injections or the use of a larger syringe, such as a 3 mL syringe, for a single administration. Planning reconstitution concentration with the final target dose in mind is critical for managing injection logistics.

Common Retatrutide reconstitution mistakes

  • Reusing a unit count from a previous vial without re-checking the new vial's diluent volume.
  • Not writing the reconstitution date on the vial itself — the in-use window is long enough that an unmarked vial becomes ambiguous.
  • Letting reconstituted retatrutide warm to room temperature for extended periods on travel days.

Frequently asked questions about Retatrutide reconstitution

How much bacteriostatic water should I use for a Retatrutide vial?
There's no single right answer — the diluent volume is the variable you control. With this 10 mg Retatrutide vial, 2 mL is a common starting point because it produces 5.00 mg/mL, which usually puts a typical dose in a comfortable 10–30 unit range on a U-100 syringe. More water = cleaner unit counts but slightly fewer doses per vial. Less water = more doses per vial but harder-to-read syringe markings. At 4 mg+ doses, mixing with 3 mL keeps unit counts under 100 — easier to read on a 1 mL syringe.
What's the difference between bacteriostatic water and sterile water?
Bacteriostatic (BAC) water contains 0.9 % benzyl alcohol as a preservative, which keeps the reconstituted vial usable for several weeks. Sterile water has no preservative — it's intended for single use, after which the vial should be discarded. For Retatrutide vials that get drawn from multiple times, BAC water is the standard choice. At 4 mg+ doses, mixing with 3 mL keeps unit counts under 100 — easier to read on a 1 mL syringe.
Can I shake the Retatrutide vial after adding water?
Don't shake it — peptides are protein-like molecules and aggressive agitation can break them. After injecting BAC water down the inner wall of the vial, swirl gently or invert the vial a few times. It should clear within a minute or two. Cloudy solution after 5 minutes of gentle swirling is a sign the powder is degraded. At 4 mg+ doses, mixing with 3 mL keeps unit counts under 100 — easier to read on a 1 mL syringe.
How long does a reconstituted Retatrutide vial stay usable?
Most lyophilized peptides reconstituted with BAC water are typically used within 4–6 weeks of refrigerated storage. The peptide itself starts to lose potency over time, and the BAC water's preservative window has limits. Writing the reconstitution date on the vial is the easiest guard against using one past that window. At 4 mg+ doses, mixing with 3 mL keeps unit counts under 100 — easier to read on a 1 mL syringe.

Related on Peptide Pilot

Save Retatrutide vials in the app

Peptide Pilot stores every vial once and derives every subsequent dose, draw, and refill reminder from those numbers automatically.

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