Common Registration Assessment, Part 1

Dexamethasone daily doses and tablet counts for the GPhC assessment

Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.

Published 28 October 2026. Independent revision material, not GPhC questions, not for patient care.

Gloved hand holding a prescription pill bottle
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS lists the usual adult dexamethasone dose as between 0.5 mg and 10 mg a day, rising to 16 mg a day for some conditions; its worked example is a 6 mg dose taken as three 2 mg tablets at the same time.

Daily doses are built up from the available tablet strengths, so each question states the strength to use.

Each question fixes the values needed for its arithmetic. Write the unit beside every step and distinguish a single dose from a daily total or course supply. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Identify the exact formulation, strength, dose and frequency supplied in the question.
  2. Convert an X mg/5 mL strength to mg/mL if a dose-to-volume conversion is needed.
  3. Calculate one dose first; for tablets or capsules divide prescribed mg by mg per unit.
  4. Scale to the stated frequency and duration only when a total quantity is requested.
  5. Apply whole-container or complete-day rounding only if the question specifies it.

Three practice questions

Work each one on paper first, then open the answer. All patients and prescriptions are fictional.

Question 1

A fictional prescription specifies dexamethasone 6 mg a day, taken as 2 mg tablets at the same time each day, for 7 days. How many tablets are needed?

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Answer: 21 tablets

Working: 6 ÷ 2 = 3 tablets per day; 3 × 7 days = 21 tablets.

Question 2

A fictional plan is dexamethasone 4 mg a day, using 500 microgram tablets. How many tablets is one day's dose?

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Answer: 8 tablets

Working: 4 mg = 4,000 micrograms; 4,000 ÷ 500 = 8 tablets.

Question 3

A fictional prescription specifies dexamethasone 16 mg a day for 5 days, using 2 mg tablets. How many tablets are needed?

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Answer: 40 tablets

Working: 16 ÷ 2 = 8 tablets per day; 8 × 5 days = 40 tablets.

NHS: How and when to take dexamethasone tablets and liquid

https://www.nhs.uk/medicines/dexamethasone-tablets-and-liquid/how-and-when-to-take-dexamethasone-tablets-and-liquid/

Where marks are lost

  • Using a remembered strength or schedule instead of the stated product.
  • Reporting a daily total when the question asks for one dose or the course.
  • Treating arithmetic as evidence that a real prescription is clinically suitable.

Frequently asked questions

Are these official assessment questions?

No. They are original revision exercises, not official GPhC questions and not for patient care.

Can a quantity calculation justify a formulation switch?

No. Follow the formulation and prescription in the exercise. Real switches and dose changes need clinical checks.

How should I check the answer?

Check the requested unit, then work backwards from the quantity to the stated dose and duration.

Sources

The questions above are original and use fictional patients and prescriptions. PreRegExamPrep is not affiliated with or endorsed by the General Pharmaceutical Council.

Practise until the method is automatic

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More calculation topics

See also the formula sheet, the eight sample questions and the approved calculator page.