Your instructions say 20 units. The vial says 100 mg/mL. Somewhere else the page said 1,000 mg. None of those three numbers is the same kind of thing, and the one you probably want — how many milligrams am I injecting — is not printed anywhere.
Here is the conversion, and then why it matters more than it should. If you want the amounts sellers actually prescribe rather than the arithmetic, the dosage chart collects them.
The arithmetic
A standard U-100 insulin syringe is graduated so that 100 units is 1 mL. That is what U-100 means. So a unit is one hundredth of a milliliter, and the syringe is measuring volume, not drug.
Two steps:
- Units ÷ 100 = milliliters. 20 units is 0.2 mL. 50 units is 0.5 mL.
- Milliliters × strength = milligrams. At 100 mg/mL, 0.2 mL is 20 mg.
That is the whole thing. The trap is step two: the same 20 units is 20 mg at 100 mg/mL and 40 mg at 200 mg/mL. The syringe cannot tell you which, because the syringe does not know what is in it.
A real vial, checked against the seller’s own numbers
One seller we cover publishes all three figures, which is rare enough to be worth using as the worked example. The vial is 10 mL at 100 mg/mL — 1,000 mg. The protocol is 20 units a day, Monday to Friday.
Run it: 20 units is 0.2 mL, which at 100 mg/mL is 20 mg a shot. A 1,000 mg vial divided by 20 mg is 50 shots. Their own page describes it as 20 mg a shot and fifty shots a vial. The numbers agree, which is how you know the specification is real rather than decorative.
Now change one thing. At 200 mg/mL — which several sellers use — that same 20 units delivers 40 mg, and the same vial volume holds twice the drug. Nothing on the syringe changes. Nothing in the instruction changes. The dose doubles.
Why you so often cannot do this
You need the strength, and plenty of sellers do not publish it. Others publish the strength and not the volume, which is just as useless: a concentration on its own tells you how strong the liquid is and nothing about how much you are getting. One seller labels its product 200 mg/mL and publishes neither a vial size nor a per-injection amount, so the number that looks like transparency resolves to nothing you can act on.
This is the same gap that makes prices incomparable. If you cannot get to milligrams, you cannot get to cost per milligram, and two sellers a hundred dollars apart might be charging the same rate — or four times it. Our 500 mg versus 1,000 mg piece walks through what the quantity difference actually buys.
What to ask for
Three numbers make a vial legible. Ask for all three:
- The strength in mg/mL.
- The volume of the vial in mL.
- The per-injection amount, in units or mL, and how often.
With those you can compute the dose, the shots per vial, how long it lasts and what a milligram costs — or put them into the vial calculator and read all four off at once. Without any one of them you cannot compute any of it. A seller who will give you all three has told you what you are buying; you can see which ones do in the provider reviews, and the dosage chart collects the protocols sellers actually publish.
One caution
This page converts numbers. It does not choose them. The amount and the frequency are a prescriber’s decision, and a vial that lasts fifty shots at 20 units lasts twenty at 50 — which changes what a month costs and is worth raising with whoever wrote the protocol, not adjusting on your own.