brain fog
noun
: a usually temporary state of diminished mental capacity marked by inability to concentrate or to think or reason clearly
Examples of brain fog in a Sentence
Recent Examples on the Web
Elevated resting heart rate, persistent fatigue, mood changes, brain fog, declining performance, more frequent illness, loss of appetite, recurring injuries, severe soreness, and sleep disturbances can all signal that your body needs a break.
—
Danielle Zickl, Health, 20 Dec. 2025
Although hypothalamic dysfunction can trigger dozens of other symptoms, the hallmark signs are insomnia (despite exhaustion), brain fog and widespread pain, the doctor said.
—Shiv Sudhakar, FOXNews.com, 20 Dec. 2025
Waiting too long can drop your blood glucose (sugar) levels, and low blood sugar may cause tiredness and brain fog.
—Christopher Bergland, Verywell Health, 4 Dec. 2025
Our day included brain fog, night sweats, insomnia, frozen shoulder, and rage.
—Gillian Telling, PEOPLE, 3 Dec. 2025
See All Example Sentences for brain fog
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Danielle Zickl, Health, 20 Dec. 2025
Although hypothalamic dysfunction can trigger dozens of other symptoms, the hallmark signs are insomnia (despite exhaustion), brain fog and widespread pain, the doctor said.
—Shiv Sudhakar, FOXNews.com, 20 Dec. 2025
Waiting too long can drop your blood glucose (sugar) levels, and low blood sugar may cause tiredness and brain fog.
—Christopher Bergland, Verywell Health, 4 Dec. 2025
Our day included brain fog, night sweats, insomnia, frozen shoulder, and rage.
—Gillian Telling, PEOPLE, 3 Dec. 2025
See All Example Sentences for brain fog
Cite this Entry
“Brain fog.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/brain%20fog. Accessed 28 Dec. 2025.
Copy CitationMedical Definition
brain fog
noun
: a usually temporary state of diminished mental capacity marked by inability to concentrate or to think or reason clearly
This brain fog can be a result of being overly stressed, tired, carrying extra weight, consuming too many calories or consistently consuming a diet poor in nutrients.—Kylie Helgens, The Gazette (Cedar Rapids, Iowa)
Kylie Helgens, The Gazette (Cedar Rapids, Iowa)Love words? Need even more definitions?
Merriam-Webster unabridged
Share