NurseSavvy Cheat SheetProcedure
Weight Conversion & mg/kg Dosing
Overview
Many drugs — and almost every pediatric drug — are ordered as milligrams per kilogram of body weight. The calculation itself is simple multiplication, but it only works from a weight in kilograms, and the weight a nurse is handed is usually in pounds. Dividing pounds by 2.2 gives kilograms, and skipping that step delivers 2.2 times the intended dose. When an order gives a total for the day in divided doses, that total is then split by the number of administrations to get each individual dose.
Interpretation
1 kg = 2.2 lb Hallmarkdivide lb by 2.2
Pounds to kilograms always gives a smaller number Hallmark
Dose = ordered mg/kg x weight in kg Hallmark
"per day in divided doses" means split the total Hallmark
"per dose" is already the single dose Hallmark
do not divide it againAlways use a measured weight in children
Technique
Worked example: 44 lb child, 10 mg/kg per day in 2 divided doses
- Convert the weight44 / 2.2 = 20 kg
- Check it shrank20 is less than 44
- Daily dose10 x 20 = 200 mg per day
- Split the day200 / 2 = 100 mg
- Give100 mg per dose
During — Monitoring
Re-weigh the child rather than using a reported weight Hallmark
Recalculate when the weight changes Hallmark
growing children outgrow their dosesHave a second nurse check pediatric calculations
Record the weight in kilograms in the chart
so nobody downstream repeats the conversionPatient Teaching
Doses change as your child grows Hallmark
Bring a current weight to appointments
Do not reuse an old bottle's dose for a new illness Hallmark
Never dose from a sibling's prescription
Report Nowescalate immediately
A kilogram figure larger than the pound figure Hallmark
the conversion was reversedA dose calculated from pounds by mistake Hallmark
2.2 times the intended amountA daily total given as a single dose Hallmark
An order with no weight recorded anywhere
A calculated dose above the safe range
Clinical Pearl
Pounds to kilograms makes the number smaller. If your kilogram figure is bigger than the pounds, you just doubled the child's dose.