The nurse’s quick guide to
I.V. drug calculations
By Kelley Miller Wilson, MSN, RN
Assistant Professor • University of Maryland School of Nursing • Baltimore, Md.
Nurses are often intimidated by the math that occurs in Example:
everyday practice. Patient safety depends on the practi- Administer heparin 5,000 units I.V. push. Available is
tioner’s ability to calculate medications correctly and in a heparin 10,000 units/mL. How many mL will you need
timely manner. This article will provide a simple and con- to administer to achieve a 5,000 unit dose?
cise method for accurate computation using basic calcula-
tions (see Quick reference: Universal formulas). 5,000 units (D)
——————— × l mL (V) = X
10,000 units (H)
Doing the math
Even with the programmable I.V. pumps used in many Answer: X = 0.5 mL
clinical settings, it’s advisable for the nurse to verify the
correct dosage by calculation once during the shift; more Calculations in mcg/minute
often if a medication is being titrated or changed. Verifica- Follow these four steps to easily calculate your patient’s
tion of correct dosages with another RN is also a wide- accurate drug dosage.
spread practice among many professionals and some- 1. Find out what’s in your I.V. bottle (drug concentration
times mandatory in institutions. or number of mL of fluid).
Another resource that’s present in many practice set- 2. Determine in which units your drug is measured
tings is the pharmacy. Pharmacists have an abundance of (units/hour, mg/hour, or mcg/kg/minute).
knowledge about medications, as well as an unparalleled 3. Know the patient’s weight in kg if your calculation is
proficiency with drug calculations; utilize their expertise weight based.
if you’re unsure of your computation.
Knowing the therapeutic dosage for the desired effect
is as important as knowing the correct calculations for the
Quick reference: Universal formulas
drug. For example, dopamine at doses of 3 to 5 mcg/kg/
minute provides a gentle dilatation of the renal arteries, Basic dosage calculation
increasing urine output with no effect on BP. At higher
D (desired dose)
doses (up to 20 mcg/kg/minute), dopamine is used for ___________________ × V (volume) = Dose
BP support. Know the medication and what effect you’re H (amount on hand)
attempting to achieve, as well as the maximum recom-
mended safe infusion dosage. I.V. drips in mcg/minute
Next time you have a patient on I.V. medication, try the mg 1,000 mcg mL 1 hour
following simple methods for calculating in a systematic ____ × ___________ × ______ × __________ = mcg/minute
way. Patient medication safety is a goal that all practitioners mL 1 mL 1 hour 60 minute
have in common—it starts with doing the math! (÷ by kg to get mcg/kg/minute)
Basic calculations I.V. drips in units/hour
The universal formula is: D (desired)
___________ × V (volume) = units/hour (# mL × units/mL = dose)
D (desired amount) H (on hand)
————————— × V (volume) = Dose
H (amount on hand)
Copyright ©2013 Wolters Kluwer Health | Lippincott, Williams & Wilkins. Unauthorized reproduction is prohibited. Nursing made Incredibly Easy! 1
I.V. drug calculations
By Kelley Miller Wilson, MSN, RN
Assistant Professor • University of Maryland School of Nursing • Baltimore, Md.
Nurses are often intimidated by the math that occurs in Example:
everyday practice. Patient safety depends on the practi- Administer heparin 5,000 units I.V. push. Available is
tioner’s ability to calculate medications correctly and in a heparin 10,000 units/mL. How many mL will you need
timely manner. This article will provide a simple and con- to administer to achieve a 5,000 unit dose?
cise method for accurate computation using basic calcula-
tions (see Quick reference: Universal formulas). 5,000 units (D)
——————— × l mL (V) = X
10,000 units (H)
Doing the math
Even with the programmable I.V. pumps used in many Answer: X = 0.5 mL
clinical settings, it’s advisable for the nurse to verify the
correct dosage by calculation once during the shift; more Calculations in mcg/minute
often if a medication is being titrated or changed. Verifica- Follow these four steps to easily calculate your patient’s
tion of correct dosages with another RN is also a wide- accurate drug dosage.
spread practice among many professionals and some- 1. Find out what’s in your I.V. bottle (drug concentration
times mandatory in institutions. or number of mL of fluid).
Another resource that’s present in many practice set- 2. Determine in which units your drug is measured
tings is the pharmacy. Pharmacists have an abundance of (units/hour, mg/hour, or mcg/kg/minute).
knowledge about medications, as well as an unparalleled 3. Know the patient’s weight in kg if your calculation is
proficiency with drug calculations; utilize their expertise weight based.
if you’re unsure of your computation.
Knowing the therapeutic dosage for the desired effect
is as important as knowing the correct calculations for the
Quick reference: Universal formulas
drug. For example, dopamine at doses of 3 to 5 mcg/kg/
minute provides a gentle dilatation of the renal arteries, Basic dosage calculation
increasing urine output with no effect on BP. At higher
D (desired dose)
doses (up to 20 mcg/kg/minute), dopamine is used for ___________________ × V (volume) = Dose
BP support. Know the medication and what effect you’re H (amount on hand)
attempting to achieve, as well as the maximum recom-
mended safe infusion dosage. I.V. drips in mcg/minute
Next time you have a patient on I.V. medication, try the mg 1,000 mcg mL 1 hour
following simple methods for calculating in a systematic ____ × ___________ × ______ × __________ = mcg/minute
way. Patient medication safety is a goal that all practitioners mL 1 mL 1 hour 60 minute
have in common—it starts with doing the math! (÷ by kg to get mcg/kg/minute)
Basic calculations I.V. drips in units/hour
The universal formula is: D (desired)
___________ × V (volume) = units/hour (# mL × units/mL = dose)
D (desired amount) H (on hand)
————————— × V (volume) = Dose
H (amount on hand)
Copyright ©2013 Wolters Kluwer Health | Lippincott, Williams & Wilkins. Unauthorized reproduction is prohibited. Nursing made Incredibly Easy! 1
