Sample Medication Calculation Problems
(Need practice with IV calculations? Scroll farther down for IV
Calculation Problems)
Do as many or as few as you need to increase your confidence in nursing
calculations
Problem #1
Your 4 year old pediatric patient weight 40 pounds. She is febrile. You need to
administer acetaminophen (Tylenol) 15mg/kg. How many mg will you administer?
(answer on next page)
Problem #2
The acetaminophen (Tylenol) packages come in liquid form 160 mg/5 mL. How many
mL will you administer to your 40 pound patient?
(answer on next page)
Problem #3
Your patient has an order for terbutaline (Brethine) 0.25 mg subcut. The pharmacy
delivers a syringe with 1mg/mL. How much will you waste in order to give the correct
dose?
(answer on next page)
Problem #4
Your hospice patient has an order for 7.5 mg of oxycodone (OxyContin) q 6
hours PRN. The tablets provided are 15 mg tablets. How many tablets will you
give for each dose?
(answer on next page)
Problem # 5
You receive an order for 60 mg of meperidine (Demerol) IM for your post surgical
patient. The injectible syringe is pre-packaged with 75 mg/ mL. How much will
you administer?
(answer on next page)
Problem #6
Your patient has been receiving digoxin (Lanoxin)125 mcg Q AM. Today his
doctor writes a new order:
Digoxin 0.25 mg PO Q AM start now
How many 125 mcg tablets will you administer?
(answer on next page)
Problem #7
Your patient has an order for vasopressin (Pitressin) 5 units subcut TID
You have on hand a 0.5 mL vial labeled 20 units/mL
How many mL will you administer?
(answer on next page)
Answers
Answer to Problem #1
First convert 40 pounds into kilograms.
Method #1: Ratio Proportion
1 kg
2.2 pounds
=
x kg
40 pounds
Cross-multiply and solve for x.
1 kg
2.2 pounds
=
Method #2: Formula Method
40 pounds
2.2 pounds
X
1 kg
=
x kg
x = 18.18 kg
x kg
40 pounds
2.2x = 40
x = 18.18 kg
Since you will administer 15mg of acetaminophen per 1 kg, you should multiply
15mg with the weight of 18.18 kg.
15mg x 18.18kg = 272.7.
You will administer 272.7 mg.
Answer to Problem #2
(You know you need 272.7 mg from the previous question)
Method #1: Ratio Proportion
160 mg
5 mL
=
272.7 mg
x mL
Method #2: Formula Method
272.7 mg
160 mg
x
5 mL
=
x mL
Cross-multiply and solve for x.
x = 8.521875 mL
120 mg
5 mL
Round. You should administer 8.5 mL.
=
272.7 mg
x mL
160 x = 1363.5
x = 8.521875 mL
Round. You will administer 8.5 mL.
You will administer 8.5 mL.
Answer to Problem #3
Method #1: Ratio Proportion
1 mL
1 mg
=
x mL
0.25 mg
Cross-multiply and solve for x.
1 mL
1 mg
=
Method #2: Formula Method
0.25 mg
1 mg
X
1 mL
=
x mL
x = 0.25 mL
x mL
0.25 mg
0.25 x = 1
x = 0.25 mL
Since you are given a syringe with 1 mg/mL and you only need 0.25 mg, then
you also just need 0.25 mL. You need to dispose (waste) 0.75 mL when the
syringe is filled 1 mL and then administer the rest of the syringe to the patient.
You will waste 0.75 mL.
Answer to Problem #4
Method #1: Ratio Proportion
15 mg
1 tablet
=
7.5 mg
x tablet
Method #2: Formula Method
7.5 mg
15 mg
x
Cross-multiply and solve for x.
Solve for x.
15 mg
1 tablet
x = 0.5 tablet
=
7.5 mg
x tablet
15 x = 7.5
x = 0.5 (or ½ tablet)
You will administer one-half a tablet.
1 tablet
= x tablet
Answer to Problem #5
Method #1: Ratio Proportion
75 mg
1 mL
=
60 mg
x mL
Method #2: Formula Method
60mg x
75 mg
Cross-multiply and solve for x.
Solve for x.
75 mg
1 mL
x = 0.8 mL
=
60 mg
x mL
1 mL
=
x mL
.
75 x = 60
x = 0.8 mL
You will administer 0.8 mL.
Answer to Problem #6
Method #1: Ratio Proportion
0.125 mcg
1 tablet
=
0.25 mcg
x mL
Method #2: Formula Method
0.25 mg
0.125 mg
Cross-multiply and solve for x.
Solve for x.
0.125 mcg
1 tablet
x = 0.25
0.125
=
0.25 mg
x tablet
0.125x = 0.25
x = .0.25/0.125
x = 2 tablets
You will administer 2 tablets.
x 1 tablet
x= 2 tablets
=
x tablet
Answer to Problem #7
Method #2: Formula Method
Method #1: Ratio Proportion
20 units
1 mL
=
5 units
x mL
5 units
20 units
x
Cross-multiply and solve for x.
Solve for x.
20 units
1 mL
x = 5 x
20
20x = 5
=
5 units
x mL
1 mL
=
x mL
1 = 1 x 1 = 0.5
4
4
x= 0.25 mL
x = 5/20
x = 0.25 mL
You will administer 0.25 mL of vasopressin.
Remember, the amount in the vial (in this case 0.5 mL) does not enter into the
calculation. The important point is the concentration (the amount of drug per
mL).
IV Calculations
IV Problem #1
Your patient has an IV ordered to be delivered at a rate of 150mL/ hr. Your infusion set
delivers 15 gtt (drops)/mL. How many drops per minute will you set the IV for?
(answer on next page)
IV Problem #2
Your patient has an IV ordered to be delivered at 75mL/hr. The infusion set delivers 10
gtt (drops)/mL. How many drops per minute will you set the IV for?
(answer on next page)
IV problem #1
Rationale:
Volume to be infused (mL) x drip rate
60 minutes
150 x 15
60
=
2250
60
=
=
# gtt/min
37.5; or round to 38 drop per minute
OR
60-minute Clock Method
¦ 10 gtts/mL
Ÿ 15 gtts/mL
¨ 60 gtts/mL
60 divided by 10 = 6
60 divided by 15 = 4
60 divided by 60 = 1
Divide mL/hr by 6
Divide mL/hr by 4.
Divide mL/hr by 1 (or simply recognize
that with a 60 gtts/mL drip set, the
number of mL/hr = the number of
gtts/min)
150 =
4
37.5; round to 38 drops per minute
IV problem #2
75 x 10 = 750 = 12.5; round to 13 drops per minute
60
60
60-minute Clock Method
¦ 10 gtts/mL
Ÿ 15 gtts/mL
¨ 60 gtts/mL
60 divided by 10 = 6
60 divided by 15 = 4
60 divided by 60 = 1
Divide mL/hr by 6
Divide mL/hr by 4.
Divide mL/hr by 1 (or simply recognize
that with a 60 gtts/mL drip set, the
number of mL/hr = the number of
gtts/min)
75 = 12.5; round to 13 drops per minute
6
End