Dosage Calculation Glossary
The terms and abbreviations you meet in med math, each defined in a sentence and explained with an example where it helps.
- Concentration
- The amount of drug in each unit of volume, such as mg/mL or units/mL; for an IV bag, the drug in the bag divided by its volume.
- Desired over Have
- The formula method: amount to give = Desired (ordered dose) ÷ Have (dose on hand) × Vehicle (the form or volume the dose on hand comes in).
- Diluent
- The liquid added to a powdered drug to reconstitute it, or to a solution to dilute it, of the type and amount the label specifies.
- Dimensional analysis
- Solving a dosage problem as one chain of fractions (conversion factors), arranged so every unit cancels except the unit of the answer.
- Drop factor
- The number of drops (gtt) that make 1 mL with a given IV tubing set, printed on the tubing package.
- gtt
- The abbreviation for drop, from the Latin gutta (plural gtts). A gravity IV's drip rate is written in gtt/min.
- IVPB
- Intravenous piggyback: a small-volume secondary infusion, usually a medication, connected to a port on the primary IV line.
- Leading and trailing zeros
- Write a zero before a decimal point (0.5 mg, not .5 mg) and none after a whole number (5 mg, not 5.0 mg), so a missed decimal point can't cause a tenfold error.
- Macrodrip
- IV tubing that delivers large drops, usually 10, 15, or 20 drops per mL, as printed on its package.
- mcg
- Microgram: one thousandth of a milligram (1 mg = 1,000 mcg).
- mEq
- Milliequivalent: one thousandth of an equivalent, the unit electrolytes such as potassium are ordered and labeled in.
- Microdrip
- IV tubing that delivers small drops, 60 drops per mL, used for small volumes and slow, precise rates.
- mL/hr
- Milliliters per hour: the flow rate an infusion pump is programmed in.
- PRN
- From the Latin pro re nata, "as the need arises": a medication order given only when the client needs it, within the limits the order sets.
- Ratio and proportion
- A dosage method that sets the known ratio (dose on hand to its volume) equal to the ordered dose over the unknown amount, then cross-multiplies.
- Reconstitution
- Adding a specified diluent to a powdered drug so it becomes a solution of a known concentration, as the label directs.
- Safe dose range
- The low-to-high dose a drug reference or label recommends, usually in mg/kg/day or mg/kg/dose, that an order is checked against.
- Titration
- Adjusting a medication's dose in steps, based on the client's response and the parameters in the order, until a target is reached.
- Units
- A measure of a drug's biological activity, used instead of weight for drugs such as heparin, insulin, and penicillin G.
- Weight-based dosing
- Ordering a drug per kilogram of body weight (mg/kg/dose or mg/kg/day), so the dose scales with the client's size.
Put the terms to work
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