The essentials
Four measurements. Different jobs.
| Measurement | What it tells you |
|---|---|
| mg or mcg | Amount of medication |
| mg/mL or mcg/mL | Amount per milliliter |
| mL | Liquid volume |
| Syringe marking | A position on the specified device.1 |
Choose the mode that matches the question on your written instructions. Concentration divides medication amount by final volume. The final-volume mode rearranges that relationship. Prescribed-volume mode uses an already prescribed amount and a written concentration. Unit conversion changes mg to mcg, or back; it does not change the amount of medication.
Final volume matters
The volume after preparation is not automatically the amount of diluent added. This tool does not choose a diluent or mixing volume.
The essentials
Check the label before the numbers
Use the current container and its current directions. Copy the unit as carefully as the number, including the decimal point. Do not combine a concentration from an old vial with directions from a new prescription. If either value is missing or unclear, ask the pharmacy before entering a guess.
A correct calculation still needs correct inputs.
The essentials
A mismatch means pause
The result checks arithmetic, not your prescription or the quality of a preparation. It cannot identify a syringe from its markings. FDA has described medication errors involving confusion between milligrams, milliliters and syringe units.1 If the result differs from your written directions, do not use it. Ask the dispensing pharmacy to resolve the difference before using the medication.
