Common Registration Assessment, Part 1

Glycerol suppository strengths and doses by age for the GPhC assessment

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

Published 10 November 2026. Independent revision material, not GPhC questions, not for patient care.

A glass carafe of water and a plain amber bottle on a wooden table
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 Glycerin Suppositories BP 4g Adult Size states that the dose is one suppository as required, that the suppository should be dipped in water before insertion, and that the 4 g suppositories are defined as adult size and are suitable for use by the elderly at the same dose.

The range also comes as Glycerin Suppositories BP 2g Children's Size and Glycerin Suppositories BP 1g Infants' Size, each dosed as one suppository as required, so the stated strength has to be matched to the stated patient.

The 4 g product information carries no children's use recommendation, which is why the size named on the prescription matters more than any calculation.

Each question fixes the values needed for its arithmetic. Write the unit beside every step and distinguish the suppository strength from the count. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Match the stated patient to the stated suppository size: 1 g infants', 2 g children's or 4 g adult.
  2. Read the stated number of suppositories used per day.
  3. Multiply the count by the strength for a total in grams, only when the question asks.
  4. Keep suppository strengths, counts and days 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 is supplied Glycerin Suppositories BP. Using the label dose, how many suppositories are used per occasion, which size applies, and what is done to the suppository before insertion?

Show the answer

Answer: One suppository as required; 4 g adult size; dipped in water

Working: The label states one suppository as required, the 4 g suppositories are defined as adult size, and the suppository should be dipped in water before insertion.

Question 2

A fictional 4-year-old child and a fictional 6-month-old infant are each supplied Glycerin Suppositories BP. Which size matches each patient?

Show the answer

Answer: 2 g Children's Size for the child; 1 g Infants' Size for the infant

Working: The range names a 2 g Children's Size and a 1 g Infants' Size, each dosed as one suppository as required; the 4 g size is adult only.

Question 3

A fictional adult uses one Glycerin Suppositories BP 4g suppository each day for 5 days. How many suppositories are used, and what is the total in grams?

Show the answer

Answer: 5 suppositories; 20 g

Working: 1 suppository x 5 days = 5 suppositories. 5 x 4 g = 20 g in total.

eMC SmPC: Glycerin Suppositories BP 4g Adult Size

https://www.medicines.org.uk/emc/product/4897/smpc

Where marks are lost

  • Reaching for the 4 g adult size for a child or infant; the label matches 1 g to infants, 2 g to children and 4 g to adults.
  • Counting grams per occasion when the label dose is one suppository as required; the count per occasion stays at one.
  • Dropping the water step; the label says the suppository is dipped in water before insertion, whatever the size.

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 glycerol suppository dose?

No. Follow the stated supply in the exercise. Real use follows the size named for the patient, one suppository as required, dipped in water before insertion.

How should I check the answer?

Match the patient to the size first, then multiply one suppository by the stated days, and by the stated grams only when a total in grams is asked.

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.