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Doses left in a vial.
Enter the amount in the vial, the water you added and the amount per dose. The calculator counts the whole doses in the vial, shows the mL and syringe units for each dose, and works out how many are left. It starts on an example.
Use the dose your prescriber gave you and the concentration printed on your vial or pharmacy label. Vialist does the math; it does not give dosing advice.
The fields start on an example (10 mg vial, 2 mL, 250 mcg per dose, 4 doses already taken). That example is not a dose for you.
Doses left in a vial
Whole doses in this vial
40 doses
- Concentration5.00 mg/mL
- mL per dose0.05 mL
- Units per dose (U-100)5
- Doses remaining36
- Left in the vial9 mg (1.8 mL)
- Dose unit differs from vial unit: 250 mcg is 0.25 mg (1000 mcg = 1 mg).
The count is arithmetic. A real vial can give a little less, so check with your pharmacist.
How the count works
The number of doses in a vial is the amount in the vial divided by the amount per dose, rounded down to a whole number. A part-dose left at the end is not counted as a dose. Keep both amounts in the same unit family: mg and mcg can be mixed (1000 mcg is 1 mg), but IU cannot be converted to mg or mcg.
whole doses = amount in the vial ÷ amount per dose, rounded down
The water does not change that count. It sets the concentration, which gives the mL and the syringe units for each dose.
Worked example, using the numbers the calculator starts on. A 10 mg vial with an example amount of 250 mcg per dose: 250 mcg is 0.25 mg, and 10 ÷ 0.25 = 40 whole doses. With 2 mL of water the concentration is 10 ÷ 2 = 5 mg per mL, so each dose is 0.25 ÷ 5 = 0.05 mL, which is 5 units on a U-100 syringe. After 4 doses, 4 × 0.25 = 1 mg is used, so 40 minus 4 = 36 doses remain and 9 mg (1.8 mL) is left in the vial. Example only. Use the dose your prescriber gave you.
Worked examples
The table fixes the vial at 10 mg and the water at 2 mL and changes only the amount per dose. The amounts are arbitrary examples chosen to show the arithmetic. They are not doses, and being in this table does not mean an amount is right for anyone. Always use the dose your prescriber gave you and the concentration on your own label.
| Amount per dose (mg) | Whole doses | mL per dose | Units per dose (U-100) | Left over (mg) |
|---|---|---|---|---|
| 0.25 | 40 | 0.05 | 5 | 0 |
| 0.3 | 33 | 0.06 | 6 | 0.1 |
| 0.5 | 20 | 0.1 | 10 | 0 |
| 1 | 10 | 0.2 | 20 | 0 |
| 3 | 3 | 0.6 | 60 | 1 |
Each cell is computed by the same code as the calculator above. Look at the 0.3 mg row: 10 ÷ 0.3 is 33.3, so the vial holds 33 whole doses and 0.1 mg is left over.
Why the real count can be lower
The calculator does arithmetic on the numbers you type. In a real vial, a little liquid stays in the vial and in the syringe (dead space), vials are not always filled to exactly the labeled amount (overfill), and some is lost while drawing. These vary by product and by syringe, so the usable amount can be less than the math says. If the exact count matters, for example when you are working out when to get another vial, ask your pharmacist how many doses to expect from your product.
Check before you count
- Confirm the amount printed on the vial and the water you added.
- Keep the vial and the dose in compatible units: mg with mcg, or IU with IU.
- Count only the doses you actually drew, and compare the result with your own record.
- Check the result against the pharmacy label, or ask your pharmacist to go through it with you.
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Questions
Straight answers.
How many doses are in a 10 mg vial?
It depends on the amount per dose: divide 10 mg by that amount and round down to a whole number. For an example amount of 0.25 mg that is 40 doses, and for 0.5 mg it is 20. Example only. Use the dose your prescriber gave you.
Does the amount of water change how many doses are in the vial?
No. The count depends only on the amount in the vial and the amount per dose. The water sets the concentration, so it changes the mL and the syringe units for each dose, not how many doses there are.
Why might my vial run out sooner than the calculator says?
The calculator counts the numbers you typed. A real vial can give a little less than that math, because dead space in the syringe, vial overfill and loss while drawing all vary. If the exact count matters to you, ask your pharmacist how many doses to expect from your product.
How do I count doses I have already taken?
Type the number into the optional field. The calculator takes those doses off the total and shows how many whole doses remain, and how much is left in the vial. Vialist Log counts each vial down for you as you log doses.
Does Vialist tell me what dose to take?
No. You enter the dose your prescriber gave you. Vialist does the unit math and keeps the record.
Try it on your own protocol.
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