These examples use generic numbers, never a specific drug — the Registry does not test regionally variable doses, and neither do we. The skill being tested is the arithmetic.
1. Convert the weight
kg = lb ÷ 2.2. A 176 lb patient weighs 80 kg. Multiplying by 2.2 by mistake is the single most common error — and it makes the dose nearly five times too large.
2. Dose by weight
Dose = weight (kg) × dose per kg. An order of 0.1 mg/kg for an 80 kg patient is 8 mg.
3. Volume to administer
Volume = dose wanted ÷ concentration on hand. To give 8 mg from a vial containing 4 mg/mL, draw up 2 mL.
4. Drip rate
Drops per minute = volume (mL) × drop factor (gtt/mL) ÷ time (minutes). To run 500 mL over 60 minutes with a 10 gtt/mL set: 500 × 10 ÷ 60 ≈ 83 gtt/min.
Unit conversions to know cold
- 1 g = 1,000 mg · 1 mg = 1,000 mcg
- 1 L = 1,000 mL
- Moving from a larger unit to a smaller one, the number gets bigger.
The errors examiners build distractors from
- Multiplying by 2.2 instead of dividing.
- Slipping a decimal place — a tenfold error.
- Halving or doubling by inverting a ratio (dividing concentration by dose).
- Using minutes and hours interchangeably in a drip rate.
CinnaEMS generates new med-math problems every round, with the distractors built from exactly these errors and the full working shown on every answer.