Common Registration Assessment, Part 1

Colecalciferol IU doses and weekly loading schedules for the GPhC assessment

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

Published 31 October 2026. Independent revision material, not GPhC questions, not for patient care.

Golden softgel capsules spilling from a glass jar
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS states that colecalciferol doses are measured in international units (IU) and that 1 microgram of vitamin D is the same as 40 IU.

The NHS lists adult loading courses of up to 300,000 IU in total, given as schedules such as 50,000 IU once a week for 6 weeks, 40,000 IU once a week for 7 weeks, 1,000 IU four times a day for 10 weeks, or 800 IU five times a day for 10 weeks.

The NHS lists a maintenance dose of 800 IU to 2,000 IU a day after loading, and a lower 400 IU daily dose for adults maintaining their vitamin D levels.

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. Check whether the dose is stated in micrograms or IU; convert micrograms to IU by multiplying by 40.
  2. Multiply a weekly dose by the number of weeks for the course total.
  3. Multiply a daily dose by the number of days, converting weeks to days first.
  4. Keep loading courses and maintenance doses separate.
  5. Check a stated course total against the stated maximum before finalising.

Three practice questions

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

Question 1

A fictional loading course is colecalciferol 50,000 IU once a week for 6 weeks. How many IU is the full course?

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Answer: 300,000 IU

Working: 50,000 IU x 6 weeks = 300,000 IU.

Question 2

A fictional maintenance dose is 20 micrograms once a day. How many IU is that per day, and over 30 days?

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Answer: 800 IU per day; 24,000 IU over 30 days

Working: 20 micrograms x 40 = 800 IU per day; 800 IU x 30 days = 24,000 IU.

Question 3

A fictional loading course is 800 IU five times a day for 10 weeks. How many IU is the full course?

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Answer: 280,000 IU

Working: 800 IU x 5 = 4,000 IU per day; 10 weeks x 7 days = 70 days; 4,000 IU x 70 days = 280,000 IU.

NHS: How and when to take colecalciferol

https://www.nhs.uk/medicines/colecalciferol/how-and-when-to-take-colecalciferol/

Where marks are lost

  • Mixing micrograms and IU in the same line of working without converting.
  • Applying a weekly schedule as if the dose were taken every day.
  • 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 course-total calculation justify changing a real loading course?

No. Follow the schedule in the exercise. Real loading and maintenance doses 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.