Retatrutide Dosage Calculator

Why a unit count from a forum is useless

The most common question about retatrutide dosing is some version of “how many units is 4 mg?” — and it has no answer on its own. Units measure volume, not mass. A unit on a U-100 syringe is one hundredth of a millilitre, always. How many milligrams sit in that volume depends entirely on how much water went into the vial.

So when someone says they draw to 40 units, that number is meaningless without their vial size and their water volume. Two people can hold identical 10 mg vials, inject the same 4 mg, and correctly draw to 40 units and 80 units respectively. Neither is wrong. They reconstituted differently.

This is why the table below lists the setup alongside every figure, and why the calculator asks for your water volume rather than assuming one.

Units per dose at common setups

All figures are units on a U-100 insulin syringe, where 100 units is 1 ml. This is arithmetic for reference — the dose column is a range of arbitrary values to illustrate the maths, not a suggestion of what to use.

Dashes mark combinations that exceed a 100 unit barrel. At that concentration the dose does not fit in one draw. Mix with less water (a stronger mix) so it takes fewer units, or split it into two draws.

The 10 mg + 2 ml row is worth reading closely. It produces the largest, easiest-to-read numbers of any setup here, but it also runs out of barrel soonest. That trade — reading precision against how much fits in one draw — is the whole of what you are choosing when you pick a water volume.

How much bac water for 5, 10, 20 or 30 mg retatrutide

There is no required volume. The water only sets the concentration, and any volume holds the same total milligrams. What most people actually want is a volume that makes the arithmetic easy, so the table shows the water that lands each vial on a round concentration, and what 1 mg and 2 mg then read as on a U-100 syringe.

5 mg vial: 0.5 ml gives 10 mg/ml, but a half-millilitre is fiddly to measure; 1 ml gives 5 mg/ml, where 1 mg is 20 units. 10 mg vial: 1 ml gives 10 mg/ml, the most common choice, because the units are simply the milligrams times ten. 20 mg vial: 2 ml gives the same 10 mg/ml. 30 mg vial: 3 ml gives 10 mg/ml if the vial can hold it; 1.5 ml gives 20 mg/ml and halves every mark.

The 10 mg/ml rows all read identically, which is the point: once you settle on one concentration, a given dose sits on the same mark whatever size vial you started with. Write that concentration on the vial so the next draw does not depend on memory.

About the dose figures circulating online

Searches for retatrutide dosing schedules and escalation charts return a lot of confident numbers. Almost all of them trace back to published clinical trial arms, where participants were titrated gradually under medical supervision across several dose levels, with monitoring and withdrawal criteria that no one reproduces at home.

A trial dose level is a description of what was studied. It is not a protocol, it was not chosen for you, and it carries none of the supervision that made it defensible in the study. This page deliberately does not reproduce those numbers as a chart, because presenting them as a schedule is the step that turns published research into apparent instructions.

What the calculator does is narrower and more honest: if you have already decided on a figure with someone qualified to advise you, it tells you which mark on the syringe corresponds to it.

Label the vial

Write the concentration and the date on the vial as soon as you reconstitute it. Retatrutide vials are frequently reconstituted at different volumes by the same person over time, and a vial with no label tells you nothing about what a unit is worth weeks later. This one habit prevents the largest category of dosing error in practice.

Reconstituted solution is kept refrigerated and is less stable than the dry powder, which is why bacteriostatic rather than sterile water is normally used. Stability varies by preparation, so follow the documentation that came with your vial instead of a general rule. The water itself keeps to a different schedule — how long bac water lasts — and the printable cheat sheet carries the concentration and units tables if you would rather not recalculate each time.

Questions

How much bac water for 10 mg retatrutide?

Any volume delivers the same total milligrams — what changes is how the dose reads on the syringe. Adding 1 ml to a 10 mg vial gives 10 mg/ml, so a 4 mg dose is 0.4 ml, which is 40 units on a U-100 syringe. Adding 2 ml gives 5 mg/ml and that same dose becomes 80 units. Choose the volume that puts the dose you draw most often on a round mark.

How much bac water for 30 mg retatrutide?

Most people pick a volume that lands on a round concentration. 3 ml in a 30 mg vial gives 10 mg/ml, so every milligram is 10 units on a U-100 syringe. 1.5 ml gives 20 mg/ml, which halves every mark (1 mg = 5 units) and keeps the draws small. Check the vial can hold the volume first: many vials top out around 3 ml, which is why 3 ml is the practical ceiling for a 30 mg vial.

How many units is 2 mg of retatrutide?

It depends on the concentration in your vial. At 10 mg/ml (10 mg vial + 1 ml, 20 mg + 2 ml, or 30 mg + 3 ml), 2 mg is 0.2 ml, which is 20 units on a U-100 syringe. At 5 mg/ml (10 mg + 2 ml) it is 40 units. At 20 mg/ml (30 mg + 1.5 ml) it is 10 units. Enter your own vial and water above to check.

How many units is 4 mg of retatrutide?

Only the concentration decides that, so the question cannot be answered from the milligrams alone. At 10 mg/ml, 4 mg is 40 units on a U-100 syringe. At 20 mg/ml it is 20 units. At 5 mg/ml it is 80 units, which will not fit a 50 unit barrel. Enter your own vial and water volume above rather than copying a unit count from someone else, because their vial was almost certainly reconstituted differently.

How do I mix retatrutide with bac water?

Wipe both rubber stoppers with an alcohol swab, draw the bacteriostatic water into a syringe, and let it run slowly down the inside wall of the retatrutide vial rather than straight onto the powder. Swirl or roll the vial gently until it is clear; do not shake it. Then write the concentration and the date on the vial, because that label is what tells you what a unit is worth later.

Why do published retatrutide doses vary so much?

The figures circulating online mostly come from published clinical trial arms, where participants were escalated gradually under supervision across a range of dose levels. Those numbers describe what was studied in a trial setting. They are not a protocol, they were not selected for you, and this page does not reproduce them as a recommendation.

Is retatrutide an approved medicine?

No. At the time of writing retatrutide is investigational — it has not been approved for general human use by the FDA, EMA or comparable regulators, and material sold online is typically labelled for laboratory research. That status is the single most important piece of context on this page.

Does the calculator work for any vial size?

Yes. It is arithmetic on the numbers you enter, so it works for 5, 10, 15, 20, 24 or 30 mg vials, or anything else, as long as you know the milligrams in the vial and the water you added.