Practice problems · Reconstitution · 5 worked
Reconstitution dosage calculation practice problems
A reconstitution problem starts with a powder. The label says what concentration the vial holds once a stated diluent is added, for example 250 mg per milliliter, and the question is how many milliliters of that solution carry the ordered dose. Read the concentration after mixing rather than the amount of diluent.
The rounding rule on this page
Every answer here is rounded once, at the end, under one stated rule: nearest tenth, half rounds up, except tablets and capsules, rates in milliliters per hour and drip rates in drops per minute, which go to the nearest whole number, half rounds up. Your program's rule may differ, and on an exam it is the one that counts.
Work each problem on paper first, then open its solution. Each one is one of the 20 problems in DoseReady's Reconstitution family, with the numbers the app drew for it.
No licensed clinician has reviewed the problem set. Where a problem and its source disagree, trust the source and what your program teaches.
Problem 1 of 5
A vial of cefazolin powder is reconstituted and then further diluted with sterile water for injection, giving 125 mg per milliliter in a final volume of 8 mL. The order reads 1,000 mg by slow intravenous push. How many milliliters are administered?
Show the worked solution
Dimensional analysis
1,000 × 1 ÷ 125 = 8
Ratio and proportion
125 mg is to 1 mL as 1,000 mg is to x
1,000 × 1 ÷ 125 = 8
x = 8 mL
Formula method
- D (desired)
- 1,000 mg
- H (have)
- 125 mg
- Q (quantity)
- 1 mL
D ÷ H × Q
1,000 × 1 ÷ 125 = 8
- The working comes to
- 8 mL
- The answer under the stated rule
- 8 mL
- Nearest tenth, half rounds up.
What each slip gives here
- Decimal point one place out80 mL or 0.8 mL
- Conversion factor inverted125,000 mL
- Conversion skipped1,000 mL
Problem 2 of 5
A vial of ampicillin powder is reconstituted with sterile water for injection, yielding 250 mg per milliliter. The order reads 500 mg intramuscularly. How many milliliters are drawn up?
Show the worked solution
Dimensional analysis
500 × 1 ÷ 250 = 2
Ratio and proportion
250 mg is to 1 mL as 500 mg is to x
500 × 1 ÷ 250 = 2
x = 2 mL
Formula method
- D (desired)
- 500 mg
- H (have)
- 250 mg
- Q (quantity)
- 1 mL
D ÷ H × Q
500 × 1 ÷ 250 = 2
- The working comes to
- 2 mL
- The answer under the stated rule
- 2 mL
- Nearest tenth, half rounds up.
What each slip gives here
- Decimal point one place out20 mL or 0.2 mL
- Conversion factor inverted125,000 mL
- Conversion skipped500 mL
What this problem is built from
Problem 3 of 5
A single-dose vial of hydrocortisone sodium succinate is reconstituted with the diluent held in its upper chamber, yielding 125 mg per milliliter. The order reads 500 mg intravenously now. How many milliliters are drawn up?
Show the worked solution
Dimensional analysis
500 × 1 ÷ 125 = 4
Ratio and proportion
125 mg is to 1 mL as 500 mg is to x
500 × 1 ÷ 125 = 4
x = 4 mL
Formula method
- D (desired)
- 500 mg
- H (have)
- 125 mg
- Q (quantity)
- 1 mL
D ÷ H × Q
500 × 1 ÷ 125 = 4
- The working comes to
- 4 mL
- The answer under the stated rule
- 4 mL
- Nearest tenth, half rounds up.
What each slip gives here
- Decimal point one place out40 mL or 0.4 mL
- Conversion factor inverted62,500 mL
- Conversion skipped500 mL
Problem 4 of 5
A vial of nafcillin powder is reconstituted with sterile water for injection, yielding 250 mg per milliliter. The order reads 1,000 mg by intravenous piggyback. How many milliliters of the reconstituted solution are added to the piggyback bag?
Show the worked solution
Dimensional analysis
1,000 × 1 ÷ 250 = 4
Ratio and proportion
250 mg is to 1 mL as 1,000 mg is to x
1,000 × 1 ÷ 250 = 4
x = 4 mL
Formula method
- D (desired)
- 1,000 mg
- H (have)
- 250 mg
- Q (quantity)
- 1 mL
D ÷ H × Q
1,000 × 1 ÷ 250 = 4
- The working comes to
- 4 mL
- The answer under the stated rule
- 4 mL
- Nearest tenth, half rounds up.
What each slip gives here
- Decimal point one place out40 mL or 0.4 mL
- Conversion factor inverted250,000 mL
- Conversion skipped1,000 mL
What this problem is built from
Problem 5 of 5
Doxycycline powder is reconstituted with sterile water for injection to 10 mg per milliliter. The order reads 200 mg by intravenous infusion. How many milliliters of the reconstituted solution are added to the infusion bag?
Show the worked solution
Dimensional analysis
200 × 1 ÷ 10 = 20
Ratio and proportion
10 mg is to 1 mL as 200 mg is to x
200 × 1 ÷ 10 = 20
x = 20 mL
Formula method
- D (desired)
- 200 mg
- H (have)
- 10 mg
- Q (quantity)
- 1 mL
D ÷ H × Q
200 × 1 ÷ 10 = 20
- The working comes to
- 20 mL
- The answer under the stated rule
- 20 mL
- Nearest tenth, half rounds up.
What each slip gives here
- Decimal point one place out200 mL or 2 mL
- Conversion factor inverted2,000 mL
What this problem is built from
Practice under your own program's rules
In DoseReady you enter your program's passing score, notation and rounding rule once. Every answer is graded under that rounding rule, and each worked solution is written in your notation where the problem allows it.
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Exam practice, never for patient care.
Guides
Other problem families
- Unit conversion practice problems for nursing students
- Tablet and capsule dosage calculation practice problems
- Oral liquid dosage calculation practice problems
- Injectable dosage calculation practice problems
- mL per hr IV rate practice problems
- IV drip rate practice problems (gtt/min)
- Infusion time practice problems
- Weight-based dosing practice problems (mg/kg)