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Injectable Dosage Calculator

This calculator was made with injectable estradiol in mind, so units used here may be inconvenient for other medicines with different concentrations or for use-cases that involve more complicated unit conversions. Please leave a comment on the neocities page (top link in the sidebar) if you have suggestions on how to improve this page.

vial concentration:mg/mL
       vial volume:mL
     syringe units:units/mL

              dose:mg
    dose frequency:days
       dose volume: ? units (? mL)

maximum injections: ?
    maximum supply: ? days (? years)

Vial

vial concentration is whatever you have in your vial in terms of milligrams per milliliter of liquid. If your vial shows a number such as 1000 mg/ 20 mL, divide the top number by the bottom number. In this case, the concentration would be 50 mg/mL.

vial volume is the total amount of liquid contained in your vial in milliliters. If your vial uses an unreduced fraction to represent concentration, like the one above, this is the number on the bottom. If you already know the concentration, then this number isn't necessary to dose correctly, but it will be harder to know how long your supply will last without it.

Syringe Units

The number on the top of the syringe units fraction is the largest unit number marked on your syringe. The number on the bottom is the volume your syringe holds when pulled up to the largest unit number. Let's say you have a syringe that goes up to 30 units, and can hold 0.3 milliliters of fluid. You would put 30 units/ 0.3 mL into the calculator.

If you don't know the volume of your syringe, but you do know whether it's a u-100 or u-40 syringe, you should divide the number of units on the syringe by the u-value. So if you have 20 units marked on a u-40 syringe, you will get 20/40, which is 0.5. This is your syringe's volume in mL. In this case, you would put 20 units/ 0.5 mL into the calculator. The u-value can tell you how much volume is in one unit on the syringe: u-100 means 0.01mL per unit, and u-40 means 0.025mL per unit. This is an important distinction, because "ten units" is not a universal measurement, and you may underdose or overdose if you buy syringes with differently sized units and don't realize it. If you don't know the u-value, and you don't know how much volume your syringe holds, do not guess. You can sacrifice one of your needles (don't reuse them, please) and pull from a container with a known volume, such as a pipette or a measuring spoon, to figure out the rough volume, and go from there.

If your syringe is measured with decimal numbers or fractions, such as 0.1, 1/2, etc. your syringe probably uses cubic centimeters (cc), which is the same as your injection volume in milliliters —— in this case, you should set both the top and bottom number of this fraction to the volume of the syringe in mL (e.g: 1.5 units/ 1.5 mL).

Supply

maximum injections and maximum supply are estimates under perfect conditions where you draw exactly your dose, every time, and there is zero loss. These numbers are a lie. Do not trust them.

All needles have dead space where additional fluid stays inside the syringe after injecting. The dead space in a 1mL syringe, for example, can be anywhere from 2 microliters to 75 microliters in the worst syringes (note: in syringes with more volume, this dead space can be larger). So if we assume the extreme case where you had an injection volume of 0.1 milliliters, were using a needle with 75 microliters of dead space, and you pulled your dose based on the needle markings like you should, you would actually pull 0.175 milliliters of fluid in total, and everything over that 0.1mL would stay in the needle head after injection. Over time, this would add up, and you would lose roughly 42% of your vial. Keep in mind that for single-use insulin needles, this number is closer to 5%, and in the majority of cases it will not be such an extreme number without you noticing —— but the loss will never be zero.

The important part here is that the actual number of injections you can get from your vial will very likely be lower than the number this calculator gives you. To give yourself leeway, you should always assume you will lose 10% of your vial when planning on when to restock; so if your vial would theoretically last you 80 injections, pretend you will only get 72, and plan accordingly. If you inject small volumes relative to the size of your syringe (0.1mL from a 2mL syringe, for example), you should assume more loss.