Short answer: Most dose calculations use one idea: desired dose divided by dose on hand, multiplied by the quantity it comes in. Infusion rates are volume divided by time, drip rates add the drop factor, and dilutions use C₁V₁ = C₂V₂. Convert units first and sense-check every answer.
01Chapter 1
The basic dose formula
Desired dose ÷ dose on hand × quantity on hand = amount to give.
Example: 60 mg is ordered. The stock is 20 mg per 5 mL. 60 ÷ 20 × 5 = 15 mL.
02Chapter 2
Infusion and drip rates
Pump rate (mL/hour) = volume ÷ time in hours. Example: 500 mL over 4 hours = 125 mL/hour.
Drip rate (drops/min) = volume × drop factor ÷ time in minutes. Example: 1,000 mL over 8 hours with a 20 drops/mL set = 1,000 × 20 ÷ 480 ≈ 42 drops/min.
03Chapter 3
Weight-based doses
Multiply the dose per kilogram by the weight. Example: 15 mg/kg for a 20 kg child = 300 mg. If the suspension is 120 mg per 5 mL, 300 ÷ 120 × 5 = 12.5 mL.
04Chapter 4
Dilutions
C₁V₁ = C₂V₂. Example: to make 200 mL of a 2% solution from a 10% stock, V₁ = 2 × 200 ÷ 10 = 40 mL of stock, made up to 200 mL.
05Chapter 5
Common traps
Most errors come from habits rather than maths.
Mixing units, such as mg and mcg or g and mg.
Using the wrong drop factor.
Forgetting to convert minutes to hours.
Not checking whether the answer is a plausible dose.
06Chapter 6
How to practise
Do five calculations every few days rather than fifty at once. Write the formula each time. Aim to finish each one in under a minute.
Check the official rules for your sitting. Practise by hand so you are comfortable either way.
It varies by profession and paper. Treat them as reliable marks and practise regularly.
This article is general educational guidance, not official advice. Exam rules, fees and timelines are set by the Dubai Health Authority and the test provider and can change, so always confirm the latest details on their official channels.
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