[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Clinical exam](https://durgical.com/en/clinical-exam/) › [General exam and vital signs](https://durgical.com/en/clinical-exam/#a-general) › Body temperature and fever patterns

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# 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](https://durgical.com/en/anatomy/hypothalamus/)

## Key points

- Fever: 38 °C or higher (rectal in children; in adults, oral above 37.2 to 37.5 °C depending on time of day). Hypothermia: below 35 °C.
- Temperature is lowest in the early morning and highest in the late afternoon; exercise, meals and the menstrual cycle raise it.
- Patterns: continuous (varies less than 1 °C), remittent (varies more but never reaches normal), intermittent (returns to normal each day), relapsing (days with fever alternating with days without).
- Fever in 48- or 72-hour cycles suggests malaria; in Colombia, dengue and other tropical fevers also matter.
- Older adults have lower baseline temperatures and can have serious infections with little or no fever.

## 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.

## Memory aid

Fever curves: 'continuous stays up, remittent dips but never lands, intermittent touches the floor'.

## 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)](https://durgical.app/estudiar/?add=/en/clinical-exam/body-temperature-and-fever-patterns/)

## See it in 3D

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

- [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/)

## Related

- [Vital signs: what they are and how to record them](https://durgical.com/en/clinical-exam/vital-signs-what-they-are-and-how-to-record-them/)
- [Fever, infection and sepsis: the bedside signs](https://durgical.com/en/clinical-exam/fever-infection-and-sepsis-the-bedside-signs/)
- [Early warning scores: NEWS2 and qSOFA](https://durgical.com/en/clinical-exam/early-warning-scores-news2-and-qsofa/)
- [Vital signs in children: how they change with age](https://durgical.com/en/clinical-exam/vital-signs-in-children-how-they-change-with-age/)

## Related conditions

- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Heat stroke and heat exhaustion](https://durgical.com/en/conditions/heat-stroke-and-heat-exhaustion/)
- [Malaria](https://durgical.com/en/conditions/malaria/)
- [Dengue](https://durgical.com/en/conditions/dengue/)
- [Febrile seizures](https://durgical.com/en/conditions/febrile-seizures/)

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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](https://medlineplus.gov/ency/article/001982.htm) (U.S. National Library of Medicine (MedlinePlus), 2025); [Fever: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003090.htm) (U.S. National Library of Medicine (MedlinePlus), 2025); [7.1 Indicators of Physiologic Functioning - Fundamentals of Nursing | OpenStax](https://openstax.org/books/fundamentals-nursing/pages/7-1-indicators-of-physiologic-functioning) (OpenStax, Rice University, 2024).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/clinical-exam/body-temperature-and-fever-patterns/