This is a unit converter, not a dosing recommendation
It does arithmetic on numbers you type in. It has no opinion on what dose you should take, and it can't tell whether your figures are sensible. Retatrutide is not licensed by the MHRA and has no approved UK dosing. Nothing here is medical advice — consult a qualified healthcare professional.
Your full dose chart
Every dose at the concentration you've entered — useful to write down and stick on the fridge.
| Dose | Volume | Units |
|---|
What the numbers mean
Concentration is how much peptide ends up in each millilitre of liquid, and it's set entirely by how much water you add. More water means a weaker solution and a bigger injection for the same dose; less water means the opposite. The peptide quantity never changes — only how far it's spread out.
Units are the marks on an insulin syringe, on the U100 scale: 100 units to a millilitre. So 0.2ml is 20 units, 0.5ml is 50 units. Most reusable peptide pens dial on the same scale, but check yours — they aren't all identical, and some have a minimum increment that won't hit every number exactly.
The full walkthrough — how to actually mix the vial, transfer it and inject — is in the mixing guide. If you're trying to work out what a full year takes, the 12-month protocol article has the vial counts and costs.
Picking your water volume
There's no single right answer, but there are two edges worth staying inside.
Too dilute and your injection volume climbs past a millilitre, which is a lot of liquid to put into subcutaneous tissue in one go — it's uncomfortable and more likely to leak back out. Too concentrated and your dose lands on such a small number of units that ordinary measurement error becomes a big percentage of the dose. Under about 5 units, a slip of a single unit is a 20% error.
The calculator flags both. If it's complaining, changing the water volume rather than the dose is usually the fix.
One that catches people out
A vial that lasts a long time on paper doesn't necessarily last that long in practice. Reconstituted peptide keeps about four to six weeks in the fridge. If the calculator says your vial holds three months of doses, some of it will expire before you get to it — which is an argument for a smaller vial or a stronger mix, not for stretching it.
The arithmetic, if you'd rather do it yourself
It's three steps and no calculator is strictly needed:
- Concentration = vial mg ÷ water ml
- Volume = your dose ÷ concentration
- Units = volume × 100
So a 10mg vial with 2ml of water is 5mg/ml. A 2mg dose is 2 ÷ 5 = 0.4ml. That's 40 units. The tool just saves you doing it at half past six in the morning.
Medical disclaimer
This calculator performs unit conversion on figures you supply. It is not medical advice and does not recommend any dose. Retatrutide is not a licensed medicine in the UK and has no MHRA-approved dosing. Always consult a qualified healthcare professional before starting, stopping or altering any medication. Check your own arithmetic — do not rely solely on this tool.