Common Registration Assessment, Part 1
Melatonin slow-release tablet counts and courses for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 25 October 2026. Independent revision material, not GPhC questions, not for patient care.
The NHS lists melatonin as 2 mg slow-release tablets; the usual dose is one tablet taken 1 to 2 hours before bedtime.
The BNF short-term course for insomnia is 2 mg once daily for up to 13 weeks; the NHS lists a maximum of 5 tablets (10 mg) once daily where a specialist adjusts the dose.
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
- Identify the exact formulation, strength, dose and frequency supplied in the question.
- Convert an X mg/5 mL strength to mg/mL if a dose-to-volume conversion is needed.
- Calculate one dose first; for tablets or capsules divide prescribed mg by mg per unit.
- Scale to the stated frequency and duration only when a total quantity is requested.
- 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 melatonin 2 mg each night for the maximum 13 weeks, using 2 mg slow-release tablets. How many tablets cover the course?
Show the answer
Answer: 91 tablets
Working: 7 nights × 13 weeks = 91 nights; 91 × 1 tablet = 91 tablets.
Question 2
A fictional plan is melatonin 2 mg each night for 28 nights, using 2 mg slow-release tablets. How many tablets cover the course?
Show the answer
Answer: 28 tablets
Working: 1 tablet × 28 nights = 28 tablets.
Question 3
A fictional plan uses the maximum 10 mg once daily, using 2 mg slow-release tablets. How many tablets is one dose?
Show the answer
Answer: 5 tablets
Working: 10 ÷ 2 = 5 tablets.
NHS: How and when to take melatonin
https://www.nhs.uk/medicines/melatonin/how-and-when-to-take-melatonin/
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
Try 15 free questions with worked answers. No sign-up required.
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See also the formula sheet, the eight sample questions and the approved calculator page.