Safe Dose Range: How to Check a Weight-Based Order

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.

Children’s doses, and many adult ones, are checked against a safe dose range before they are given. The range comes from a drug reference or the label and is usually written per kilogram, either per day or per dose.

To check an order:

1. Convert the weight to kilograms if needed (divide pounds by 2.2).
2. Multiply the weight by the low and the high end of the range.
3. If the range is per day and the order is per dose, divide the daily limits by the number of doses, or multiply the ordered dose by it.
4. Compare. Inside the range, the dose is safe to give; outside it, hold the dose and contact the prescriber.

A child who weighs 18 kg has an order for 200 mg every 8 hours. The drug reference lists a safe range of 20 to 40 mg/kg/day in divided doses. Is the dose safe?

Solve for

Is the ordered dose safe?

Weight

18 kg

Doses per day

3

Safe range low end

20 mg/kg/day

Safe range high end

40 mg/kg/day

Ordered single dose

200 mg

Formula Dose = mg/kg × weight in kg.

1. Safe daily range = 20 to 40 mg/kg/day × 18 kg = 360 to 720 mg/day.
2. Divided every 8 hours is 3 doses a day: 120 to 240 mg per dose.
3. The ordered 200 mg is within 120 to 240 mg, so the dose is safe to give.
4. Maximum safe single dose: 240 mg. 240 mg is exact, so no rounding is needed.

Answer 240 mg

The ranges in this example are for practice only. In clinical care, use the current label or your facility’s drug reference.

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