There is much speculation as to what the word run means in the idiom run a fever. There are no definitive answers to this question. An important caution when studying idioms is that you must realize that many idioms are not compositional. Not all the words used have a precise idiomatic use that can be ascertained with a discreet meaning. The phrase taken as a whole simply means what it means!
Note that a person can run a fever but cannot walk a fever or crawl a fever. It would not be possible to ever ascertain the meaning of the idiom by examining the word run itself. Therefore, an insistence on the true historical reason for using the word in the phrase is perhaps not a sensible use of your time.
Also: run a temperature
Meaning of Idiom “Run a Fever”
To run a fever means to have a body temperature that is higher than normal (98.6° F/37° C), usually as a result of an illness (virus, bacterial infection, etc.)
Sentence Examples
“My son was running a fever so I kept him home from school. I’ll leave for work as soon as the babysitter comes.”
“My nose is stuffy, I have a sore throat, and I’m running a fever. I don’t think I’m going anywhere today.”
“My daughter was prone to ear infections when she was little. She would have incredible ear pain and run a fever for days. It turns out she has narrow ear canals.”
“You’re not running a temperature but you look awful and you’re clearly coming down with something.”
“Is it normal to run a fever after you get a flu shot?”
“You’re not running a fever anymore. That’s good. But you’d better take it easy for the rest of the day, at least.”
“You’re flushed and you were moaning. I think you’re running a fever.” — Twelve Monkeys (1996)
“Tell them they have to sleep.” “Haise is running a fever of 104.” “Thirteen, we’ve had another request from the flight surgeon that you fellas get more sleep.” — Apollo 13 (1995)
Origin Of Run a Fever
Used since the early 1900s. The word fever means to have a body temperature higher than normal or expected. It was derived from the Old French fievre (“fever”). The French word came from the Latin febris (“a fever”), a word with Proto-Indo-European roots. This became the Old English fefer, fefor which evolved in the Middle English fever, fevere. 1
The word run does not indicate movement but is perhaps used in the sense of maintain in a certain state, according to a thread a English Stack Exchange. 2 Perhaps a simpler explanation for the use of the word run is just “to have.”
30 English Idioms With Run
- ”fever.” Wiktionary. 12 Apr 2025, 10:48 UTC. 25 May 2025, 23:27 <https://en.wiktionary.org/w/index.php?title=fever&oldid=84534863>.
- Various. “Etymology – ‘Running a Fever’ Origin – English Language & Usage Stack Exchange.” English Language & Usage, english.stackexchange.com/questions/177222/running-a-fever-origin. Accessed 25 May 2025.