Weight-based dosage (mg/kg)
Some doses depend on the weight of the person. Find the dose in mg, and then the volume or the number of doses.
For practice only. Not for clinical use. The drug names and numbers are made up. Always follow your school's and your facility's rules.
Practice problem
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The order is Quorvane 10 mg/kg. The patient weighs 154 lb. Round the weight to the nearest tenth of a kg first. What dose do you give, in mg?
Round to the nearest tenth.
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How to solve it
Change pounds to kilograms: divide by 2.2. Multiply the dose for each kilogram by the weight in kilograms. If the order is for one day, divide it by the number of doses.
Worked example
The order is Calvorin 25 mg/kg. The patient weighs 84.1 kg. What dose do you give, in mg?
Solution
- 25 mg/kg × 84.1 kg = 2,102.5 mg.
Formula: Dose = dose per kg × weight in kg
Answer: 2,102.5 mg
Questions
How do I use a dose in mg/kg?
Multiply the dose for each kilogram by the weight in kilograms. For example, 5 mg/kg for a person of 20 kg is 100 mg.
What if the weight is in pounds?
Divide the pounds by 2.2 to get kilograms. Do this before you do the rest of the math.
What if the order is mg/kg/day?
The order gives the total for one day. Find the total dose. Then divide it by the number of doses each day.
Should I round the weight?
Follow the rounding rule of the problem. Round only at the end. This keeps the answer more exact.