Common Registration Assessment, Part 1

Diclofenac tablet daily doses and gel application limits for the GPhC assessment

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

Published 29 October 2026. Independent revision material, not GPhC questions, not for patient care.

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The NHS lists the usual dose of diclofenac tablets or capsules as 75 mg up to a maximum of 150 mg a day, usually taken 2 to 3 times a day.

For the gel, the NHS lists about 2 to 4 grams per application, used 2 to 4 times a day, with no more than 4 applications in any 24-hour period.

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. Calculate one dose first; for tablets divide prescribed mg by mg per tablet.
  3. Scale to the stated frequency for a daily total before comparing with any maximum.
  4. Keep grams of gel and mg of tablets as separate units; never mix them in one step.
  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 diclofenac 50 mg three times a day using 50 mg tablets. How many tablets is that per day, and what is the daily dose in mg?

Show the answer

Answer: 3 tablets (150 mg)

Working: 1 tablet × 3 doses = 3 tablets per day; 3 × 50 mg = 150 mg per day, the stated daily maximum.

Question 2

A fictional plan uses 4 g of diclofenac gel per application, 4 times in 24 hours. What is the total amount of gel used that day?

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Answer: 16 g

Working: 4 g × 4 applications = 16 g per day, at the stated maximum of 4 applications.

Question 3

A fictional prescription specifies diclofenac 75 mg a day in divided doses using 25 mg tablets. How many tablets is that per day?

Show the answer

Answer: 3 tablets

Working: 75 mg ÷ 25 mg = 3 tablets per day.

NHS: How and when to take or use diclofenac

https://www.nhs.uk/medicines/diclofenac/how-and-when-to-take-or-use-diclofenac/

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.

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More calculation topics

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