Common Registration Assessment, Part 1
Tablet quantities for reducing regimens
Count tablets across changing daily doses, alternate-day schedules and pack rounding, using fictional regimens.
Published 7 October 2026. Independent revision material, not GPhC questions, not for patient care.
A reducing regimen needs more than one daily-dose calculation. Split it into fixed-dose blocks, calculate tablets for each block and add the totals. Do not apply the starting dose to the whole prescription.
These examples use fictional Drug X and state when tablets may be split. They test counting, not taper design. A real schedule needs the prescriber’s instructions and drug-specific guidance. Never infer the next step from the pattern.
The method
- List each dose block and its duration.
- Divide daily dose by tablet strength.
- Multiply tablets per day by treatment days.
- For alternate-day dosing, count actual dose dates.
- Add block totals, then apply pack rounding only if instructed.
Three practice questions
Work each one on paper first, then open the answer. All drugs and patients are fictional.
Question 1
Drug X is prescribed at 20 mg daily for 5 days, then 10 mg daily for 7 days. Tablets contain 5 mg. How many tablets are needed?
Show the answer
Answer: 34 tablets
Working: First: 20 ÷ 5 = 4/day; 4 × 5 = 20. Second: 10 ÷ 5 = 2/day; 2 × 7 = 14. Total = 34.
Question 2
Drug X is 15 mg daily for 4 days, then 7.5 mg daily for 6 days. Tablets contain 5 mg and may be split into equal halves. How many whole tablets are needed in total?
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Answer: 21 tablets
Working: First: 3/day × 4 = 12. Second: 1.5/day × 6 = 9. Total = 21 whole tablets.
Question 3
Drug X is 10 mg daily for 7 days, then 10 mg on days 8, 10, 12 and 14 only. Tablets contain 5 mg. Supply whole packs of 20 only. How many packs are needed?
Show the answer
Answer: 2 packs
Working: There are 11 dose days. Each needs 2 tablets, so 22 are required. 22 ÷ 20 = 1.1 packs; round up to 2.
A table catches missing days
Use columns for dose, strength, tablets per dose and dose days. Write zero-dose days explicitly for intermittent schedules. That makes an off-by-one error easier to see than a single long calculator entry.
Where marks are lost
- Using the initial daily dose throughout.
- Assuming every alternate-day block starts with a dose.
- Splitting tablets without permission in the stem.
Frequently asked questions
Should I round every half-tablet dose up?
Not when splitting is explicitly permitted. Keep the half-tablet count and sum the block before finding the whole-tablet total.
Is this a steroid taper recommendation?
No. Drug X and the schedules are fictional. The exercise only counts an already specified regimen.
Sources
- The Pharmaceutical Journal, quantities to supply and using provided formulae
- GPhC, 2026 assessment specification and permitted items
The questions above are original and use fictional drugs. 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.
More calculation topics
- Dose by weight calculations for the GPhC assessment
- Volume to give: liquid medicine calculations
- Percentage strength calculations: w/v, w/w and ratios
- Dilution calculations with C1V1 = C2V2
- Infusion rate calculations in mL per hour
- Drip rate calculations: drops per minute
- Body surface area calculations
- Creatinine clearance (Cockcroft-Gault) calculations
- Moles and millimoles calculations
- Displacement volume calculations for reconstitution
- Quantity to supply calculations
- Using a provided formula in calculations
- Dose information from packaging and labels
- Diluting a stock to a lower strength
- Medicine cost and switch calculations
- Rounding rules in calculations
- Enteral feed rate calculations
- Electrolyte content over time
- Infusion dose per kg per hour
- Rounding doses to measurable volumes
- Relative risk and relative risk reduction
- Absolute risk reduction and number needed to treat
- Odds ratio and confidence intervals
- Relative versus absolute risk reduction
- Loading dose and volume of distribution
- Top-up doses from measured drug levels
- Salt correction factors
- Mass and molar drug concentrations
- Half-life and falling drug levels
- Steady-state concentration and infusion rate
- Bioavailability and equivalent oral doses
- Oral maintenance dose and dosing interval
- Elimination rate constant and half-life
- Accumulation towards steady state
- Ratio strengths and one in X
- Serial dilution factors
- Mixing solutions of different strengths
- Equivalent doses from provided conversion tables
- Thresholds and dose-banding algorithms
See also the formula sheet, the eight sample questions and the approved calculator page.