This free Dosage Calculations Practice Test #9 covers safe-dose range checks: calculating the safe range from a child’s weight, comparing daily totals with mg/kg/day ranges and single doses with mg/kg/dose ranges, converting pounds, grams and micrograms, maximum-dose caps, and what to do when a dose is too high or too low. Work through 10 timed questions, then check every answer with the full rationales below. No sign-up required.
All 10 Questions With Answers & Rationales
Prefer to work at your own pace? Every question from the timed quiz above is listed here in full. Choose your answer, then tap Show Answer & Rationale to check it.
Question 1: Daily range with divided doses
A child who weighs 15 kg is prescribed a medication 150 mg orally every 8 hours. The facility drug reference lists a safe range of 20–40 mg/kg/day in divided doses. Which conclusion is correct?
- A. Unsafe: the daily dose is above the maximum
- B. Safe: the daily dose is within the safe range
- C. Unsafe: the dose is below the minimum
- D. The dose cannot be checked without the child's height
Show Answer & Rationale
Answer: B. Safe: the daily dose is within the safe range
Rationale: Find the safe daily range: 15 kg × 20 mg = 300 mg/day and 15 kg × 40 mg = 600 mg/day. Find the prescribed daily total: 150 mg × 3 doses (every 8 hours) = 450 mg/day. 450 mg falls between 300 and 600 mg, so the dose is safe. "Below the minimum" is the error of comparing one 150 mg dose with the 300 mg daily minimum: always compare a daily total with a daily range. Height is needed only for body surface area (BSA) dosing, not mg/kg dosing. Safe ranges differ between drug references, indications and ages, so use the reference your facility approves.
Question 2: Convert pounds to kilograms first
A child who weighs 55 lb is prescribed a medication 350 mg every 6 hours. The drug reference lists a safe range of 40–50 mg/kg/day divided every 6 hours. What should the nurse conclude? (1 kg = 2.2 lb)
- A. Safe: give the dose as prescribed
- B. Unsafe: the dose is below the safe range of 2,200–2,750 mg/day
- C. Unsafe: each dose should be 1,000–1,250 mg
- D. Unsafe: the dose is above the safe range, so hold it and contact the prescriber
Show Answer & Rationale
Answer: D. Unsafe: the dose is above the safe range, so hold it and contact the prescriber
Rationale: Convert first: 55 lb ÷ 2.2 = 25 kg. Safe range: 25 × 40 = 1,000 mg/day to 25 × 50 = 1,250 mg/day. Prescribed: 350 mg × 4 doses = 1,400 mg/day, which is above the maximum. The nurse holds the dose and contacts the prescriber before giving it. 2,200–2,750 mg/day is what you get if you multiply by pounds instead of kilograms, which more than doubles the range and hides the overdose. 1,000–1,250 mg is the daily range, not a single dose (per dose would be 250–312.5 mg).
Question 3: Per-dose range
An infant who weighs 8 kg is prescribed a medication 40 mg every 6 hours. The drug reference lists a safe dose of 4–6 mg/kg/dose every 6 hours. Which conclusion is correct?
- A. Safe: 40 mg is within the range of 32–48 mg per dose
- B. Unsafe: the dose is above the maximum of 6 mg per dose
- C. Unsafe: the daily total of 160 mg is above 48 mg
- D. Unsafe: the dose is below 4 mg/kg/day
Show Answer & Rationale
Answer: A. Safe: 40 mg is within the range of 32–48 mg per dose
Rationale: This reference gives the range per dose (mg/kg/dose), so compare the single dose. 8 kg × 4 mg = 32 mg and 8 kg × 6 mg = 48 mg per dose. 40 mg is within 32–48 mg, so it is safe. Comparing the daily total (160 mg) with a per-dose range is the most common mix-up: read the units on the reference carefully. mg/kg/dose means compare one dose; mg/kg/day means compare the 24-hour total. "6 mg per dose" forgets to multiply by the weight.
Question 4: A dose that is too low
A child who weighs 22 kg is prescribed an antibiotic 100 mg orally every 12 hours. The drug reference lists a safe range of 25–50 mg/kg/day divided every 12 hours. What is the nurse's best action?
- A. Give the dose, because a dose below the range cannot cause harm
- B. Give 300 mg instead so the daily total reaches the safe range
- C. Hold the dose and contact the prescriber, because the dose is below the safe range
- D. Give the dose and document that it is within the safe range
Show Answer & Rationale
Answer: C. Hold the dose and contact the prescriber, because the dose is below the safe range
Rationale: Safe range: 22 × 25 = 550 mg/day to 22 × 50 = 1,100 mg/day. Prescribed: 100 mg × 2 = 200 mg/day, well below the minimum. A dose below the range is not automatically safe: an antibiotic given at a subtherapeutic dose may not treat the infection and can promote resistance. The nurse does not change a dose independently (that requires a new prescription), so the correct action is to hold and contact the prescriber, then document the conversation. Documenting the dose as safe would be inaccurate.
Question 5: Safe range per dose from a daily range
A child who weighs 24 kg has a new prescription for a medication every 8 hours. The drug reference lists a safe range of 10–15 mg/kg/day divided every 8 hours. What is the safe range for each dose?
- A. 240–360 mg per dose
- B. 30–45 mg per dose
- C. 10–15 mg per dose
- D. 80–120 mg per dose
Show Answer & Rationale
Answer: D. 80–120 mg per dose
Rationale: Daily range: 24 × 10 = 240 mg/day and 24 × 15 = 360 mg/day. Every 8 hours = 3 doses in 24 hours. Per dose: 240 ÷ 3 = 80 mg and 360 ÷ 3 = 120 mg. 240–360 mg is the daily range, not a single dose. 30–45 mg comes from dividing by 8 (the hours between doses) instead of by 3 (the number of doses). 10–15 mg forgets to multiply by the weight. To find doses per day, divide 24 by the interval: q6h = 4, q8h = 3, q12h = 2.
Question 6: Weight-based dose with a maximum cap
A child who weighs 45 kg is prescribed a medication 650 mg orally. The drug reference lists 15 mg/kg/dose, not to exceed 500 mg per dose. Which conclusion is correct?
- A. Safe: 650 mg is less than the weight-based dose of 675 mg
- B. Safe: a child who weighs 45 kg can receive any adult dose
- C. Unsafe: 650 mg is above the 500 mg maximum per dose
- D. Unsafe: the dose is below the weight-based dose
Show Answer & Rationale
Answer: C. Unsafe: 650 mg is above the 500 mg maximum per dose
Rationale: The weight-based dose is 45 × 15 = 675 mg, but the reference caps a single dose at 500 mg. The cap always wins: the safe dose is the lower of the two numbers, so the most this child may receive per dose is 500 mg. 650 mg exceeds the cap and the nurse should contact the prescriber. Heavier children commonly reach the maximum dose, which is why references list one. Weight alone does not make a child eligible for an adult dose. Caps differ between drugs and references, so check the one for the specific product.
Question 7: Neonate weight in grams
A neonate who weighs 2,500 g is prescribed a medication 20 mg every 12 hours. The drug reference lists a safe range of 10–15 mg/kg/day divided every 12 hours. Which conclusion is correct?
- A. Unsafe: 40 mg/day is above the maximum of 37.5 mg/day
- B. Safe: 20 mg per dose is less than 37.5 mg
- C. Unsafe: the safe range is 25,000–37,500 mg/day
- D. Safe: 40 mg/day is within the safe range
Show Answer & Rationale
Answer: A. Unsafe: 40 mg/day is above the maximum of 37.5 mg/day
Rationale: Convert grams to kilograms: 2,500 g ÷ 1,000 = 2.5 kg. Safe range: 2.5 × 10 = 25 mg/day to 2.5 × 15 = 37.5 mg/day. Prescribed: 20 mg × 2 = 40 mg/day, which is above the maximum. Comparing one 20 mg dose with the daily maximum hides the overdose. 25,000–37,500 mg/day is the result of multiplying by grams instead of kilograms. Small errors matter most in neonates, so many facilities require an independent double check on neonatal doses.
Question 8: Safe range in micrograms
A child who weighs 14 kg is prescribed a medication 0.07 mg every 12 hours. The drug reference lists a safe range of 8–12 mcg/kg/day divided every 12 hours. Which conclusion is correct? (1 mg = 1,000 mcg)
- A. Unsafe: 0.14 mg/day is below 112 mcg/day
- B. Safe: 140 mcg/day is within 112–168 mcg/day
- C. Unsafe: 70 mcg per dose is above 12 mcg/kg
- D. Safe only if the child weighs more than 20 kg
Show Answer & Rationale
Answer: B. Safe: 140 mcg/day is within 112–168 mcg/day
Rationale: Put everything in the same unit. Safe range: 14 × 8 = 112 mcg/day to 14 × 12 = 168 mcg/day. Prescribed: 0.07 mg = 70 mcg per dose × 2 doses = 140 mcg/day, which is within range. "0.14 mg is below 112" compares milligrams with micrograms: 0.14 mg is 140 mcg. 70 mcg ÷ 14 kg = 5 mcg/kg per dose, not more than 12 mcg/kg. Microgram drugs are often high-alert, so double-check the decimal point and always use a leading zero and never a trailing zero (write 0.07 mg, not .07 mg or 0.070 mg).
Question 9: Remaining dose under a daily maximum
A child who weighs 20 kg has a PRN prescription for a medication 250 mg every 6 hours as needed. The drug reference lists a maximum of 50 mg/kg/day. The child has received three 250 mg doses in the past 24 hours. How many more mg can the child receive in this 24-hour period without exceeding the maximum?
- A. 250 mg
- B. 0 mg
- C. 1,000 mg
- D. 750 mg
Show Answer & Rationale
Answer: A. 250 mg
Rationale: Daily maximum: 20 × 50 = 1,000 mg in 24 hours. Already given: 3 × 250 mg = 750 mg. Remaining: 1,000 − 750 = 250 mg, so one more dose can be given within the limit. 1,000 mg is the total daily maximum, not what is left, and 750 mg is what has already been given. Before any PRN dose, check the medication record for every dose given in the past 24 hours, including the same drug in combination products, and ask caregivers what was given at home.
Question 10: Choosing the safe order
A child who weighs 10 kg needs a medication. The drug reference lists a safe range of 30–40 mg/kg/day divided every 6 hours. Which prescription is within the safe range?
- A. 50 mg every 6 hours
- B. 120 mg every 6 hours
- C. 90 mg every 6 hours
- D. 40 mg every 6 hours
Show Answer & Rationale
Answer: C. 90 mg every 6 hours
Rationale: Safe range: 10 × 30 = 300 mg/day to 10 × 40 = 400 mg/day, or 75–100 mg per dose given 4 times a day. 90 mg × 4 = 360 mg/day, within range. 50 mg × 4 = 200 mg/day and 40 mg × 4 = 160 mg/day are below the minimum (too low to be effective). 120 mg × 4 = 480 mg/day is above the maximum. Working out the per-dose range first (300 ÷ 4 and 400 ÷ 4) lets you check each order at a glance.
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