Brain fog

Brain fog is not a formal diagnosis but a patient-reported syndrome of cognitive sluggishness: trouble concentrating, mild forgetfulness, slow word-finding, mental fatigue out of proportion to physical effort. It became culturally widespread post-COVID-19, but the differential is much older and broader: undertreated hypothyroidism, B12 / folate / vitamin D deficiency, iron-deficiency anaemia, poorly controlled diabetes (both hyperglycaemia and hypoglycaemia), electrolyte disturbance (hyponatraemia in older patients), obstructive sleep apnoea, depression and anxiety, perimenopause, chronic alcohol use, side effects of medications (anticholinergics, benzodiazepines, antihistamines), and post-viral syndromes. Lab work-up is targeted at correctable contributors first.

• Sleep deprivation, obstructive sleep apnoea — single biggest underdiagnosed cause.
• Hypothyroidism — even subclinical disease blunts cognition.
• Iron, B12, folate or vitamin D deficiency — correctable nutritional causes.
• Diabetes — both highs and lows degrade concentration.
• Depression, anxiety, chronic stress — overlap is large; both subjective and objective.
• Perimenopause — estrogen fluctuations.
• Post-viral (long-COVID, post-EBV) — emerging area; partly inflammatory, partly autonomic.
• Medications — anticholinergics, benzodiazepines, opioids, antihistamines.
• Chronic alcohol or cannabis use.

First-line screen for correctable contributors: CBC (anaemia), ferritin, comprehensive metabolic (sodium, glucose), HbA1c, TSH, vitamin B12, folate, 25-OH vitamin D. Add HIV and hepatitis screening if epidemiologically appropriate. Mediora.AI flags the deficiencies and metabolic patterns; brain fog without a correctable lab finding usually leads to a primary-care sleep-screening and depression-screening conversation rather than further blood work.