Clinical exam · General exam and vital signs

Body temperature and fever patterns !

Vital sign

How temperature is measured, when there is a fever and what shapes the fever curve can take over several days.

Updated 2026-11-01

See it in 3D: Hypothalamus

What it is

Core temperature is held near 37 °C by the thermoregulatory centre in the hypothalamus. Fever is a regulated rise of that set point, almost always from infection or inflammation; hyperthermia, by contrast, is a rise without a change in set point, when heat production or gain outstrips heat loss. The shape of the temperature curve and its relation to the pulse help with diagnosis.

Reference values

Normal in adults: 36.5 to 37.3 °C, average 37 °C (MedlinePlus).
Older adults: a somewhat lower normal range (OpenStax places it at 35.8 to 36.9 °C orally).
Fever in children: rectal 38 °C or higher; oral 37.5 °C or higher; axillary 37.2 °C or higher.
As a rule rectal reads highest and axillary lowest; always record the route.

How to measure it

Choose the route by age and condition: rectal or axillary in infants; oral, tympanic or axillary in older children and adults.
Oral: wait a few minutes if the patient has just eaten, drunk or smoked; place the tip under the tongue to one side, mouth closed.
Axillary: dry the armpit, place the tip in the centre of the axilla and hold the arm against the chest until the thermometer signals.
Tympanic: pull the ear up and back in adults (down and back in young children) and seal the canal.
Rectal (infants): lubricate the tip and insert it gently just over one centimetre while holding the child.
Read and record the value with route and time; if abnormal, repeat with another device or route.
For a fever pattern, chart the temperature several times a day over several days alongside the pulse.

What abnormal values mean

Fever: infections (bacterial, viral, parasitic), inflammatory and autoimmune disease, cancers (lymphomas), drug reactions and thrombosis.
Fever with shaking chills and spikes: bacteremia or malaria; fever with retro-orbital pain and myalgia: dengue.
Hyperthermia with a normal set point: heat stroke; it does not respond to antipyretics.
Hypothermia: cold exposure, severe sepsis, hypothyroidism, and frail or malnourished older patients.
Fever or hypothermia with tachycardia, tachypnea and confusion should prompt thoughts of sepsis.
Pulse-temperature dissociation (high fever with a relatively slow pulse): typhoid fever and some intracellular infections.

Common errors

Measuring orally right after the patient had a cold or hot drink.
Damp armpit or poorly placed thermometer: falsely low reading.
Not recording the route, so readings cannot be compared.
Relying on a hand on the forehead to rule out fever.

Test yourself

Think of the answer, then tap the question to see it.

What is the difference between fever and hyperthermia?

In fever the hypothalamus raises its set point; in hyperthermia the set point is normal but the body gains or makes more heat than it can lose, as in heat stroke.

At what time of day is adult body temperature usually lowest?

In the early morning; it rises through the day and is highest in the late afternoon.

Which fever pattern returns to normal temperature every day?

Intermittent fever: fever spikes alternate with periods of normal temperature within the same day.

Why can a serious infection go unnoticed in an older adult?

Because their baseline temperature is lower and the febrile response may be weak or absent; a small rise from their baseline is already significant.

Add to my cards (4)

See it in 3D

The structures of Durgical's 3D anatomy where it is found.

Hypothalamus

← All of the clinical exam

Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: Body temperature norms: MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine (MedlinePlus), 2025); Fever: MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine (MedlinePlus), 2025); 7.1 Indicators of Physiologic Functioning - Fundamentals of Nursing | OpenStax (OpenStax, Rice University, 2024).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.