Short answer: Drug calculations for nurses in the DHA exam become simple with one habit: write the units, convert first, then use desired over have times volume. Five problem types cover most questions: tablets, liquids, weight-based doses, pump rates and drip rates. Finish by asking whether the answer is plausible.
Drug calculations for nurses: one method
Most nurses lose marks to slips, not to hard maths. This page gives one routine. First, write what is ordered and what is on hand, with units. Second, convert so both use the same unit. Third, divide what you want by what you have, then multiply by the volume or number of units the stock comes in. Fourth, check that the answer makes sense.
The wider dosage calculations guide covers dilutions and traps. This guide is the quick routine to rehearse. Meddex is independent and is not connected to the Dubai Health Authority (DHA) or Prometric, so confirm at the source whether a calculator is provided in the exam.
Convert units before anything else
Keep a small ladder in your head: 1 g is 1000 mg, 1 mg is 1000 mcg and 1 L is 1000 mL. To go down a step, multiply by 1000. To go up, divide by 1000. Example: 0.25 mg is 250 mcg. Write the new unit beside the number so you can see it.
Type 1: tablets
Example, written by Meddex. Ordered: 750 mg. Stock: 250 mg tablets. 750 divided by 250 is 3, so give 3 tablets. If the answer were 0.3 or 30 tablets, you would stop and check.
Type 2: liquids
Example, written by Meddex. Ordered: 120 mg. Stock: 40 mg in 5 mL. 120 divided by 40 is 3. Three times 5 mL is 15 mL. Say the sentence in full: I want 120, I have 40 in 5 mL, so I need 15 mL.
Type 3: weight-based doses
Example, written by Meddex. Ordered: 15 mg per kg. The patient weighs 18 kg. The dose is 15 times 18, which is 270 mg. The stock is 125 mg in 5 mL. 270 divided by 125 is 2.16. Multiply by 5 to get 10.8 mL. Check the weight is in kilograms and that the dose does not exceed the stated maximum.
Type 4: pump rates
Example, written by Meddex. Give 1000 mL over 8 hours. 1000 divided by 8 is 125, so set the pump to 125 mL an hour. For a small volume over minutes, convert minutes to hours first. 100 mL over 30 minutes is 100 divided by 0.5, which is 200 mL an hour.
Type 5: drops per minute
Without a pump, the drop rate is volume times drop factor, divided by time in minutes. The drop factor is printed on the set and is normally given in the question. Example, written by Meddex. 500 mL over 4 hours with a set of 20 drops per mL. 500 times 20 is 10 000. Four hours is 240 minutes. 10 000 divided by 240 is about 41.7, so run 42 drops a minute. Round only at the end, and follow any rounding rule in the stem.
The plausibility check that catches ten-fold errors
A misplaced decimal point can give ten times the intended dose, which is why this check matters most. Ask three questions. Is the answer close to the usual dose? Is it a sensible number of tablets or millilitres for one administration? Does the unit match what the question asks? If any answer is no, redo the calculation from the units.
How to practise
Do five problems, one of each type, every other day. Say each step in words. The medication safety five rights guide shows why the dose right sits at the centre of safe practice.
Where marks are lost and how to avoid it
Most wrong answers come from four slips. Using grams where milligrams are asked. Forgetting to multiply by the stock volume at the end. Using pounds as if they were kilograms. Dividing minutes by hours the wrong way round. Write the unit after every line and read the last line of the question again before you give the answer.
You may meet the same skills as nursing dosage calculations, nursing drug dose questions or nurse medication maths. The method does not change. Practise on paper first, then on the on-screen tools your test allows, once you have confirmed what they are.
Related guide
For the formulas laid out for nurses and doctors, including dilutions, see DHA exam dosage calculations.
Frequently asked questions
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.
Last updated .