Common Registration Assessment, Part 1

Oseltamivir capsule doses and five-day courses for the GPhC assessment

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

Published 6 November 2026. Independent revision material, not GPhC questions, not for patient care.

A woman in bed blowing her nose into a tissue
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The manufacturer's UK product information for oseltamivir 30 mg hard capsules states that for adults and adolescents aged 13 years and over the recommended treatment dose is 75 mg twice daily for 5 days, and that treatment should be started as soon as possible within the first two days of the onset of symptoms of influenza.

The same information states that for children aged 1 to 12 years the twice daily treatment dose depends on body weight: 30 mg for 10 kg to 15 kg, 45 mg for over 15 kg to 23 kg, 60 mg for over 23 kg to 40 kg, and 75 mg for over 40 kg.

It also states that a 75 mg dose can be given as one 75 mg capsule or as one 30 mg capsule plus one 45 mg capsule.

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 a supply period. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Identify the stated dose in milligrams and the number of doses each day.
  2. Multiply the dose by the daily dose count for the daily milligram total.
  3. Multiply the daily total or capsule count by the stated number of days for a course total.
  4. Keep milligrams and capsules separate; convert only when the question asks.

Three practice questions

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

Question 1

A fictional adult takes oseltamivir 75 mg twice daily for the stated 5-day treatment course. How many milligrams is this over the whole course?

Show the answer

Answer: 750 mg

Working: 75 mg x 2 doses = 150 mg each day. 150 mg x 5 days = 750 mg over the course.

Question 2

A fictional child weighing 20 kg takes the stated twice daily treatment dose for that weight band. How many milligrams is this each day?

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Answer: 90 mg

Working: Over 15 kg to 23 kg is the 45 mg dose band. 45 mg x 2 doses each day = 90 mg a day.

Question 3

A fictional adult takes each 75 mg dose as one 30 mg capsule plus one 45 mg capsule, twice daily for 5 days. How many capsules is this over the course?

Show the answer

Answer: 20 capsules

Working: 2 capsules each dose. 2 capsules x 2 doses = 4 capsules each day. 4 capsules x 5 days = 20 capsules.

eMC SmPC: Tamiflu 30 mg Hard Capsules

https://www.medicines.org.uk/emc/product/8050/smpc

Where marks are lost

  • Counting a twice daily course as once daily over the 5 days.
  • Choosing the adult 75 mg band for a child whose weight falls in a lower band.
  • Counting doses instead of capsules when a 75 mg dose is given as one 30 mg plus one 45 mg capsule.

Frequently asked questions

Are these official assessment questions?

No. They are original revision exercises, not official GPhC questions and not for patient care.

Does this calculation decide a real oseltamivir course?

No. Follow the stated prescription in the exercise. Real courses depend on age, weight, kidney function and whether treatment or prevention is intended.

How should I check the answer?

Check the requested unit, then work backwards from the quantity to the stated dose and course length.

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

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More calculation topics

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