Reconstitution
calculator
Enter what is in the vial and how much solvent you added. It returns the concentration, the volume for one dose, and where that lands on an insulin syringe. No account, no signup, and nothing you type leaves your browser.
This does arithmetic, nothing else. It converts between milligrams, micrograms, millilitres and syringe units using the numbers you type. It does not know what you are reconstituting, it has no opinion on what your dose should be, and it is not medical advice. Decisions about what to take, and how much, belong with a qualified healthcare professional.
How the calculation works
Three steps, each of which you can check by hand. Take a 5 mg vial with 2 mL of solvent added and a 250 mcg dose:
1. Concentration
Divide the peptide in the vial by the volume of solvent you put in. The powder itself adds a negligible amount of volume at these quantities, so the solvent volume is the one that counts.
5 mg ÷ 2 mL = 2.5 mg/mL
2. Volume for one dose
Put the dose in the same unit as the concentration first — 250 mcg is 0.25 mg, since a milligram is a thousand micrograms. Then divide.
0.25 mg ÷ 2.5 mg/mL = 0.1 mL
3. Units on the syringe
A U-100 insulin syringe is graduated so that 100 units is 1 mL. That is what the U-100 means, and it is the only assumption in this step. Multiply millilitres by 100.
0.1 mL × 100 = 10 units
Written as one line, with the dose in micrograms and the peptide in milligrams:
units = (dosemcg ÷ 1000) ÷ (peptidemg ÷ solventmL) × 100
Why the solvent volume is a choice, not a given
Nothing about the vial dictates how much solvent to add. Adding less makes a more concentrated solution and a smaller draw; adding more makes a weaker solution and a bigger draw. The dose is identical either way — only the number of units on the barrel changes.
That matters at the extremes. A draw of under about two units sits in the first couple of graduations, where a small misreading is a large proportion of the dose. A draw past the end of the barrel cannot be measured at all. The calculator flags both, because both are solved the same way: change the solvent volume, not the dose.
Questions
Not to the arithmetic — a millilitre is a millilitre, and the concentration comes out the same. It matters a great deal to whether a vial can be used more than once, because bacteriostatic water contains a preservative and sterile water does not. Follow the labelling on the product you actually have, and your pharmacist rather than a web page.
They are the same measurement on a different scale. An insulin syringe is U-100, meaning 100 units of volume per millilitre, so one unit is 0.01 mL. The calculator shows both because vials are labelled in milligrams and millilitres while syringes are labelled in units, and the conversion is where most mistakes happen.
By an amount too small to read on a syringe at these quantities. A few milligrams of lyophilised powder displaces a fraction of a microlitre. The calculator treats the solvent volume as the final volume, which is the same simplification every reconstitution chart makes.
No. There is nowhere to store it: the page is a static file, the arithmetic runs in your browser, and the site sets no cookies, runs no analytics and makes no third-party requests. The shareable link holds the numbers in the URL itself, which is why it works without an account.
Yes. TideTracker has the same calculator built in, along with a syringe view, inventory and dose logging, and it keeps all of it on your iPhone. The calculator here is free and needs nothing installed.
Related
- Converting between mg, mcg, mL and syringe units — every conversion on this page, written out
- Reading an insulin syringe — what the numbers on the barrel mean, and how the three sizes differ
- TideTracker — the same calculator, plus inventory and dose logging, kept on your iPhone