7.2 Temperature Measurement

CNA Certified Nursing Assistant

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1 Introduction to the CNA Exam

1.1 About the CNA Certification Exam 1.2 Exam Content Areas 1.3 Clinical Skills Evaluation 1.4 How to Use This Course

2 Role and Responsibilities

2.1 CNA Scope of Practice 2.2 The Healthcare Team 2.3 Delegation and Supervision 2.4 Documentation and Reporting 2.5 Time Management and Organization 2.6 Professionalism and Work Ethics

3 Communication and Interpersonal Skills

3.1 Verbal Communication 3.2 Nonverbal Communication 3.3 Active Listening 3.4 Communication with Special Needs Patients 3.5 Cultural Sensitivity and Diversity 3.6 Handling Difficult Communication Situations

4 Infection Control

4.1 Chain of Infection 4.2 Hand Hygiene 4.3 Personal Protective Equipment (PPE) 4.4 Standard Precautions 4.5 Transmission-Based Precautions 4.6 Cleaning, Disinfection, and Sterilization

5 Safety and Emergency Procedures

5.1 Fall Prevention 5.2 Fire Safety 5.3 Body Mechanics and Safe Lifting 5.4 Restraints and Alternatives 5.5 Emergency Response Procedures 5.6 Disaster Preparedness

6 Personal Care Skills

6.1 Bathing and Showering 6.2 Oral Hygiene and Denture Care 6.3 Hair Care, Grooming, and Shaving 6.4 Dressing and Undressing 6.5 Perineal Care 6.6 Toileting and Incontinence Care

7 Basic Nursing Skills

7.1 Vital Signs Overview 7.2 Temperature Measurement 7.3 Pulse Measurement 7.4 Respirations Measurement 7.5 Blood Pressure Measurement 7.6 Positioning, Transfers, and Mobility

8 Mental Health and Cognitive Care

8.1 Understanding Dementia 8.2 Communication with Dementia Residents 8.3 Dementia Care Strategies 8.4 Depression and Anxiety in the Elderly 8.5 Abuse Recognition and Reporting

9 Legal and Ethical Considerations

9.1 Residents' Rights 9.2 HIPAA and Confidentiality 9.3 Advance Directives and End-of-Life Care 9.4 CNA Scope of Practice 9.5 Ethical Principles in Healthcare 9.6 Documentation and Reporting

7.2 Temperature Measurement

Key Takeaways Explain This Topic AI

Rectal is the most accurate but most invasive route; axillary is least accurate but least invasive

Rectal runs about 1 degree F higher than oral; axillary runs about 1 degree F lower than oral

Wait 15-30 minutes after eating, drinking, or smoking before taking an oral temperature

Never leave a rectal thermometer unattended; hold it in place and insert only 1/2 to 1 inch

Fever (pyrexia) is above 100.4 degrees F; report a temperature above 101 degrees F or below 97 degrees F
Last updated: June 2026

Routes and Their Normal Ranges

Body temperature reflects the balance between heat the body produces and heat it loses. The number you get depends on where you measure, so always document the route.

Normal Temperature by Route

Route Normal Range Time Required
Oral 97.6-99.6 degrees F Until digital beep (3-5 min for glass)
Rectal 98.6-100.6 degrees F Until beep
Axillary 96.6-98.6 degrees F 8-10 min for glass; until beep digital
Tympanic (ear) 97.6-99.6 degrees F 1-2 seconds
Temporal artery (forehead) 97.6-99.6 degrees F 1-2 seconds

Memory anchor: rectal is about 1 degree F higher than oral; axillary is about 1 degree F lower than oral. So if an oral reading would be 98.6, the same patient reads roughly 99.6 rectally and 97.6 axillary.

Oral Temperature

Use for alert, cooperative adults who can hold the probe under the tongue. Do not use it for unconscious patients, those receiving oxygen by mask, confused patients who may bite, infants, or anyone with a mouth injury. After hot or cold food, drink, or smoking, wait 15-30 minutes , otherwise the reading is falsely high or low. Place the probe under the tongue to one side (the sublingual pocket), have the patient close the lips, and read at the beep.

Rectal, Axillary, and Electronic Methods
Rectal Temperature

The most accurate route because it samples a closed core cavity, but it is the most invasive. Use it when the oral route is impossible, but avoid it with rectal surgery, diarrhea, hemorrhoids, patients on blood thinners (bleeding risk), and cardiac patients (insertion can stimulate the vagus nerve and slow the heart).

Procedure essentials: provide privacy, glove, lubricate the probe cover, position the patient side-lying (left Sims' position), insert only 1/2 to 1 inch in an adult, and hold it in place the entire time . Never walk away from a rectal thermometer.

Axillary Temperature

The least accurate route but the least invasive, useful when both oral and rectal are contraindicated, or for screening. Dry the armpit, center the probe in the axilla, hold the arm snug against the body, and label the result "axillary."

Electronic and Disposable Thermometers

Type Strength Limitation
Digital oral/rectal Fast, accurate, easy to read Needs a fresh probe cover each use
Tympanic (ear) 1-2 seconds Earwax, infection, or lying on the ear distort it
Temporal artery Non-invasive, fast Sweating or a cool forehead skews it
Disposable single-use No cross-contamination One use only; screening accuracy

For a tympanic reading, pull the ear up and back in adults (down and back in infants under 1 year) to straighten the canal.

Naming Abnormal Temperatures

Term Meaning Threshold
Fever (pyrexia) Elevated temperature Above 100.4 degrees F oral
Hyperthermia Dangerously high Above 104 degrees F
Hypothermia Dangerously low Below 95 degrees F
Afebrile No fever Within normal range

Report immediately any temperature above 101 degrees F or below 97 degrees F , a sudden change from baseline, or a normal number paired with the patient feeling hot, chilled, or sweaty.

Fahrenheit, Celsius, and Common Test Traps

Most United States facilities chart in Fahrenheit , but you may see Celsius on imported equipment or in education materials, so know the anchor points: 98.6 F equals 37.0 C, 100.4 F (the fever line) equals 38.0 C, and 104 F (hyperthermia) equals 40.0 C. You will not be asked to do hand calculations on the skills exam, but a written knowledge test may pair the two scales, so memorize those three matched values rather than a formula.

Probe Covers, Cleaning, and Infection Control

Every oral, rectal, and tympanic reading uses a fresh disposable probe cover , which is both an accuracy and an infection-control step. Rectal and oral probes are color-coded, usually red for rectal and blue or green for oral , and they are never interchanged. After a rectal temperature, remove gloves and perform hand hygiene before touching anything else, because the perineal area is a reservoir for bacteria such as E. coli. A common written-test trap asks what to do if the same digital unit must serve both routes; the answer is to use the dedicated color-coded probe and a new cover, not to wipe and reuse.

A Worked Scenario

A confused resident on oxygen by mask needs a temperature. The CNA should not choose the oral route: the patient cannot reliably hold the probe, and the mask interferes. Tympanic or temporal artery is fast and safe here; axillary is acceptable but slower and least accurate. If the nurse needs a true core reading and there is no rectal contraindication, the rectal route is most accurate, but the CNA confirms it is allowed first.

Why Temperature Trends Matter

A single number means little without context. A resident whose temperature climbs from a baseline 97.8 F to 99.8 F over a shift may be developing an infection even though 99.8 F is still inside the "normal" band. This is why you compare to baseline and report a rising trend , not just a number that crosses a fixed line. Document the time with every reading so the nurse can see the slope, and never alter or estimate a temperature to make it look normal.