Lessons · Nursing · weight-based doses, mg/kg
Weight-based dosing: the order is per kilogram
A weight-based order gives an amount per kilogram; multiply it by the patient's weight in kilograms for the dose. If the order is per day, divide by the number of doses in the day.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
Every paediatric order and many adult ones are written per kilogram, because a dose that fits 80 kg does not fit 18 kg. The weight is converted to kilograms first, and then it is one multiplication. The problem gives the per-kg figure; the nurse gives the arithmetic.
How to think about it
Convert the weight to kilograms if it is in pounds. Multiply the per-kg amount by the kilograms; write mg on the result. If the order says per day, divide by the doses per day. If it then has to become tablets or millilitres, D / H × Q takes over from there.
Worked example
Ordered 10 mg/kg per dose. Patient 66 lb.The order is a rate, mg per kg. The weight is in the wrong unit.
66 / 2.2 = 30 kgPounds to kilograms first.
Dose = 10 × 30 = 300 mgPer-kilogram amount times kilograms. Three hundred milligrams.
Ordered 20 mg/kg/day in 2 doses, 30 kg: 20 × 30 = 600 mg/day; 600 / 2 = 300 mg per doseA per-day order: the whole day first, then divided among the doses.
Your turn
Ordered 5 mg/kg per dose for a 40 kg patient. Write the line.
Dose = 5 × = 200 mg
Solve one, graded on the server
The trap
Using the pounds. 10 mg/kg × 66 = 660 mg, more than double the dose, and the number looks as tidy as the right one. The order says per kilogram, so the weight is in kilograms before anything is multiplied.