Method

1. Safe daily range = weight (kg) × recommended minimum and maximum mg/kg/day.
2. Prescribed daily total = single dose × doses per day.
3. The prescribed total should fall inside the range.

Worked example

20 kg child; reference range 20-40 mg/kg/day; order 250 mg every 12 h. Range = 400-800 mg/day; prescribed = 500 mg/day → within the recommended range.

Notes

• An out-of-range result means stop and verify with the prescriber or pharmacist – it does not by itself mean the order is wrong (indications differ).
• Use the range for the specific indication and route from a current drug reference.

Educational use only – for checking and learning medication math. Always verify doses against the order, the drug reference and a pharmacist. Reviewed 2026-08-23.