You walk into a room and forget why. You reach for a simple word and it isn’t there. You read the same email three times. Work that used to take an hour takes the whole afternoon.
“Brain fog” sounds mild. For many people with long COVID, it’s the symptom that costs them the most, at work, at home, and in confidence.
Brain fog is a recognized part of long COVID
The RECOVER study (Thaweethai et al., JAMA, 2023) developed a research definition of long COVID from thousands of participants. Brain fog was among the symptoms that best distinguished people with long COVID from those without it. It is not a vague complaint. It is one of the condition’s defining features.
What it feels like
- Trouble finding words, or saying the wrong word
- Short-term memory lapses
- Difficulty concentrating or following conversations
- Slower thinking and processing
- Losing your train of thought mid-sentence
- Mental exhaustion after tasks that used to be easy
- Feeling detached or “not all there”
What may be driving it
Brain fog after COVID likely has more than one cause, and the combination varies from person to person. Areas researchers are investigating include:
- Blood flow when upright. Studies of people with ME/CFS, a condition that overlaps heavily with long COVID, have found reduced blood flow to the brain during head-up tilt, even when heart rate and blood pressure look acceptable. If your fog is worse standing or sitting up and better lying down, that pattern matters. See our page on POTS after COVID.
- Immune activity. Research has found autoantibodies and markers of persistent immune activation in some people with long COVID.
- Brain chemistry. Imaging research published in 2026 reported reduced dopamine transporter signal in a small group of long COVID patients, which may be relevant to motivation and focus. The findings are early.
- Sleep disruption. Poor or unrefreshing sleep is common after COVID and makes cognitive symptoms worse.
- Post-exertional crashes. For many people, fog spikes a day or two after physical or mental overexertion. See our page on crashing after exertion.
Why “just push through it” often backfires
Cognitive effort is exertion. If you tend to crash after a demanding day, forcing through mental work can deepen the fog for days afterward. Tracking when fog worsens, including what you did 24 to 72 hours earlier, often reveals a pattern.
How it is evaluated
- Pattern and timing: whether fog changes with posture, time of day, meals, sleep, or exertion.
- Related symptoms: rapid heart rate on standing, fatigue, gut changes, or new food and chemical sensitivities.
- Ruling out other contributors: thyroid problems, anemia, low B12, sleep apnea, medication effects, and mood disorders can all affect thinking.
- Coordination: with neurology or neuropsychology when formal cognitive testing or imaging is warranted.
When to get emergency care
Call 911 immediately for:
- sudden confusion,
- trouble speaking or understanding speech,
- facial drooping,
- weakness on one side of the body, or
- sudden severe headache.
These can be signs of a stroke and are not typical brain fog.
Serving Oklahoma City, Tulsa, and all of Oklahoma
Venturis Clinic sees patients from Oklahoma City and surrounding areas, including Tulsa, and from across Oklahoma. Brain fog is usually one piece of a larger pattern. Our Long COVID Treatment in Oklahoma City page explains how we approach it as a whole.
Frequently asked questions
Does long COVID brain fog go away? Many people improve over time, though recovery is often uneven. Understanding what worsens it is a useful first step.
Is brain fog a sign of brain damage? Not necessarily. Several drivers, such as reduced blood flow when upright, poor sleep, and post-exertional crashes, involve how the brain is functioning rather than permanent injury. Research is ongoing.
Why is my brain fog worse some days? Posture, sleep, stress, exertion in the prior days, and meals can all shift it. Tracking these often shows a pattern.
Could it be early dementia? Post-COVID brain fog is different from dementia, but significant or progressive memory changes should be evaluated.
Want to understand what’s clouding your thinking? Book a free 15-minute discovery call, or learn more about long COVID care in Oklahoma City.
This page is for educational purposes and is not a substitute for individual evaluation.
By Alvin Philipose, DC, ICCP
Sources
- Thaweethai T, et al. Development of a definition of postacute sequelae of SARS-CoV-2 infection. JAMA. 2023;329(22):1934–1946.
- van Campen CMC, Verheugt FWA, Rowe PC, Visser FC. Cerebral blood flow is reduced in ME/CFS during head-up tilt testing even in the absence of hypotension or tachycardia. Clinical Neurophysiology Practice. 2020;5:50–58.
- Liu et al. Dopamine transporter imaging in long COVID. eBioMedicine. 2026. doi:10.1016/j.ebiom.2026.106339