Common Registration Assessment, Part 1

Tirzepatide weekly escalation steps and pen supply for the GPhC assessment

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

Published 14 November 2026. Independent revision material, not GPhC questions, not for patient care.

A glucose meter with a blank screen, a white lancet pen and a blue awareness ribbon on a pink background
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 Mounjaro (tirzepatide) KwikPen gives a starting dose of 2.5 mg once a week for 4 weeks, then an increase to 5 mg once a week. Further increases, when needed, are made in steps of 2.5 mg after at least 4 weeks on the current dose, up to a maximum of 15 mg once a week.

Each KwikPen contains 4 doses of 0.6 ml, so one pen covers 4 weeks of once-weekly injections, and packs contain 1 or 3 pens. The 2.5 mg KwikPen holds 10 mg of tirzepatide in 2.4 ml of solution.

If a dose is missed, the product information says to inject as soon as possible within 4 days of the missed dose, or to skip it and take the next dose on the regularly scheduled day if more than 4 days have passed. The day of weekly injection can be changed as long as at least 3 days separate two doses. NHS guidance on tirzepatide reflects the same once-weekly schedule and missed dose advice.

Each question fixes the values needed for its arithmetic. Keep the week count and the dose step beside every answer. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Start at 2.5 mg once a week for 4 weeks, then increase to 5 mg once a week.
  2. Allow at least 4 weeks on a dose before any further 2.5 mg step up.
  3. Treat 15 mg once a week as the maximum dose.
  4. Count one KwikPen as 4 once-weekly doses, so 4 weeks of supply.
  5. For a missed dose, check whether more than 4 days have passed before deciding to inject or to skip.

Three practice questions

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

Question 1

A fictional patient injects 2.5 mg once a week for 4 weeks, then 5 mg once a week. How many KwikPens cover the first 12 weeks, and what total mg of tirzepatide is injected in that time?

Show the answer

Answer: 3 pens; 50 mg in total

Working: Each pen holds 4 once-weekly doses, so 12 weeks needs 12 / 4 = 3 pens. Weeks 1 to 4 give 4 x 2.5 mg = 10 mg and weeks 5 to 12 give 8 x 5 mg = 40 mg, so 10 + 40 = 50 mg in total.

Question 2

A fictional patient on 10 mg once a week misses the usual Monday injection and remembers on Thursday. What does the product information say to do?

Show the answer

Answer: Inject as soon as possible, because Thursday is within 4 days of the missed dose

Working: Monday to Thursday is 3 days, inside the 4-day window, so the missed dose is injected as soon as possible and the weekly schedule resumes. If more than 4 days had passed, the dose would be skipped.

Question 3

A fictional patient wants to move a weekly injection from Monday to Friday. Is this allowed under the product information, and why?

Show the answer

Answer: Yes; Friday is 4 days after the previous Monday dose, and a day change is allowed as long as at least 3 days separate two doses

Working: Monday to Friday leaves 4 days between doses. The product information allows the day of weekly administration to change provided the time between two doses is at least 3 days.

eMC SmPC: Mounjaro 2.5 mg KwikPen solution for injection in pre-filled pen

https://www.medicines.org.uk/emc/product/15481/smpc

Where marks are lost

  • Stepping up before completing at least 4 weeks on the current dose.
  • Staying on the 2.5 mg starting dose beyond the first 4 weeks when the schedule moves to 5 mg.
  • Counting one KwikPen as one dose instead of 4 once-weekly doses.
  • Injecting a missed dose when more than 4 days have already passed.

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 dose?

No. Follow the stated prescription in the exercise. Real dosing follows the prescriber and the product information for the named product.

How long does one pen last?

Each KwikPen contains 4 doses of 0.6 ml, so at one dose a week a pen lasts 4 weeks and a 3-pen pack lasts 12 weeks.

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.