Common Registration Assessment, Part 1

Nystatin liquid doses and daily frequency for the GPhC assessment

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

Published 30 October 2026. Independent revision material, not GPhC questions, not for patient care.

Patient having their throat examined in a medical setting
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS lists the usual dose of nystatin for adults, babies and children with oral thrush as 1ml taken 4 times a day, leaving at least 3 hours between doses.

The NHS lists the dose to prevent oral thrush as 1ml taken once or twice a day.

The NHS advises taking nystatin liquid after a meal or some food, measuring it with an oral syringe, medicine spoon or dropper rather than a kitchen teaspoon, and keeping it in the mouth for at least 30 seconds if possible.

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 whether the question is treatment (4 times a day) or prevention (once or twice a day).
  2. Calculate one day first: dose volume times the stated frequency.
  3. Scale to the stated duration for a course total.
  4. For spacing questions, add the stated minimum gap repeatedly from the first dose time.
  5. Keep ml per dose and hours between doses as separate units.

Three practice questions

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

Question 1

A fictional patient takes 1ml of nystatin 4 times a day for 7 days to treat oral thrush. How many ml is the course?

Show the answer

Answer: 28ml

Working: 1ml x 4 times a day = 4ml a day; 4ml x 7 days = 28ml.

Question 2

A fictional patient takes the first of 4 daily doses at 8am, leaving at least 3 hours between doses. What is the earliest time for the fourth dose?

Show the answer

Answer: 5pm

Working: 8am + 3 hours = 11am; 11am + 3 hours = 2pm; 2pm + 3 hours = 5pm for the fourth dose.

Question 3

A fictional bottle contains 100ml of nystatin liquid. At the treatment dose of 1ml 4 times a day, how many full days will it last?

Show the answer

Answer: 25 days

Working: 1ml x 4 times a day = 4ml a day; 100ml / 4ml = 25 days.

NHS: How and when to take or use nystatin

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

Where marks are lost

  • Using the prevention frequency for a treatment question.
  • Starting the 3-hour gap count at the wrong dose time.
  • Treating arithmetic as evidence that a real course 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 bottle-days calculation justify stopping early?

No. Follow the course in the exercise. Real courses follow the prescriber's instructions even if symptoms settle sooner.

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

Try 15 free questions with worked answers. No sign-up required.

Try 15 free questionsSee pricing

More calculation topics

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