Common Registration Assessment, Part 1
Lithium tablet strengths and daily doses for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 24 October 2026. Independent revision material, not GPhC questions, not for patient care.
The NHS lists standard lithium tablets as 250 mg and slow-release tablets as 200 mg, 400 mg and 450 mg. The BNF starting dose is 200 to 600 mg once daily at night, adjusted by blood levels.
The NHS advises staying on the same brand of lithium once treatment has started.
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 dose is lithium 400 mg at night, using 200 mg slow-release tablets. How many tablets is one dose?
Show the answer
Answer: 2 tablets
Working: 400 ÷ 200 = 2 tablets.
Question 2
A fictional dose is lithium 600 mg at night, using 400 mg and 200 mg slow-release tablets together. How many tablets is one dose?
Show the answer
Answer: 2 tablets
Working: 400 + 200 = 600 mg, so 1 tablet of each strength = 2 tablets.
Question 3
A fictional daily amount is lithium 800 mg, using 400 mg slow-release tablets. How many tablets is that day?
Show the answer
Answer: 2 tablets
Working: 800 ÷ 400 = 2 tablets.
NHS: How and when to take lithium
https://www.nhs.uk/medicines/lithium/how-and-when-to-take-lithium/
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.