Common Units in Nursing

andré davey; Julia Langham

9 Common Units in Nursing

Learning Outcomes

By the end of this chapter, learners will be able to:

identify common units of measurement for amount, mass and liquid volume in the metric system, and
identify the correct abbreviations for common units of measure.

Understanding the Metric System

Types of Units

It’s likely you have learned about the metric system (also known as The International System of Units) at some point in your past education, but perhaps some of the details are a little fuzzy. The four types of metric measurements most commonly used in nursing are: grams, metres, litres. and moles. Respectively, these units measure the amount of mass (weight), length, volume (capacity), and substance.

Difference Between Volume and Capacity

You might think of litres as a way to measure the volume of a liquid, but it’s not the most precise definition. Volume is a measure of how much space an object takes up, always measured in cubic units, such as cubic centimetres. Can you remember calculating the volume of cubes and rectangular solids in high school geometry? Multiplying the height, width and depth of box would give you the volume. Capacity is the measurement of how much of a substance can be inside an object, which could be matter existing in any state. Although there are many units to measure capacity, litre is most commonly used unit for measuring liquid matter. For use in nursing work, litre is commonly referred to as a measure of volume.

Base Units and Sizes of Measurements

When units of measure go up and down in size, they do so by a power of ten. A prefix is added to the base unit to indicate the size of the unit. For instance, a unit ten times larger than a gram is a decagram. You will not often see all of the possible units of measure being used in nursing work, so for the purposes of this text we will focus on the units you will use most often.

Table 9.1 Common Base Units
Metric Prefix	Symbol	Power of 10	Meaning	Multiply By
tera	T	10¹²	one trillion	1,000,000,000,000
giga	G	10⁹	one billion	1,000,000,000
mega	M	10⁶	one million	1,000,000
kilo	k	10³	one thousand	1,000
hecto	h	10²	one hundred	100
deca	da	10¹	ten	10
deci	d	10-¹	one tenth	[latex]\frac{1}{10}[/latex]
centi	c	10-²	one hundredth	[latex]\frac{1}{100}[/latex]
milli	m	10−³	one thousandth	[latex]\frac{1}{1000}[/latex]
micro	μ	10−⁶	one millionth	[latex]\frac{1}{1000000}[/latex]
nano	n	10−⁹	one billionth	[latex]\frac{1}{1,000,000,000}[/latex]
pico	p	10−¹²	one trillionth	[latex]\frac{1}{1,000,000,000,000}[/latex]

Commonly Used Units

The following table outline units which are commonly used in medication orders and in medication administration in Canada. You should understand what these units measure and how to convert from one unit of measure to another. Occasionally, you will see measurements given using the US customary system of measure, derived from the British imperial system of measure. You may need to convert between units of the metric and imperial systems of measurement. Refer to the conversion table in this textbook for commonly used conversion factors.

Table 9.2 Common Units
Quantity	Abbreviation	Measure
Amount	i.u.	international unit
Amount	mEq	milliequivalent
Amount	mmol	millimole
Volume	mL	millilitre
Volume	L	litre
Mass	mcg	microgram
Mass	mg	milligram
Mass	g	gram
Mass	kg	kilogram
Length	cm	centimetre
Length	m	metre

Defining Units^[1]

Within the table above, each unit of measure is defined in the glossary of this textbook. Click on the word to view the definition if you are unable to define the unit of measure in your own words. If using this book in another format, you can find the glossary at the back of the book.

Practice Set 9.1: Unit Abbreviations

Case Study

Scenario A: IV Fluid Rate Calculation

A patient named John is in the emergency department with dehydration. The nurse needs to administer Normal Saline (0.9% Sodium Chloride) at a rate of 75 mL/hour. John is to receive IV fluids for 6 hours.

Question: What is the total volume of Normal Saline that John will receive in litres?

Answer:

John will receive a total of 0.45 litres of Normal Saline.

Scenario A Solution:

Rate of infusion: 75 mL/hour
Total time: 6 hours
Total volume in mL: [latex]75\text{mL/hour} \times 6 \text{ hours } = 450\text{mL}[/latex]
Convert to litres: [latex]\displaystyle \frac{450\text{mL}}{1000} = 0.45[/latex]

Scenario B: Medication Dosage Calculation

You are working as a nursing student in a clinic in Halifax. A physician prescribes Amoxicillin for a patient diagnosed with a urinary tract infection (UTI). The prescribed dosage is 500 mg every 8 hours. The medication is available in 250 mg tablets.

Questions:

How many tablets will you administer per dose?
If the patient needs to take the medication for 7 days, how many total tablets will they require?

Answers:

B 1) 2 tablets per dose

B 2) 42 tablets total

Scenario B 1 Solution: To find out how many tablets to administer per dose:

[latex]\begin{align*} \text{ Tablets per dose } = \text{ Prescribed dosage/ Dosage per tablet } \\ = \frac{500 mg}{250 \text{ mg/tablet } }= 2 \text{ tablets } \end{align*}[/latex]

Scenario B 2 Solution: To find the total tablets for 7 days:
[latex]\begin{align*} \text{ Total tablets } & = \text{ Tablets per dose } \times \text{ Doses per day } \times \text{ Days Total tablets } \\ & = 2 \text{ tablets } \times 3 \text{ doses day } \times 7 \text{ days } = 42 \text{ tablets} \end{align*}[/latex]

Chapter Credit

Adapted from Chapter 6 Common Units in Nursing in A Guide for Numeracy in Nursing by Julia Langham, CC BY 4.0.

Case Studies are new content.

National Institute of Standards and Technology. (2020, January). SI units. https://www.nist.gov/si-redefinition/definitions-si-base-units ↵

License

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