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Symptom Decision Tree

Match your primary symptom pattern to the action. Multiple matches? Start from the top — ruling out medical causes comes first.

Start Here

Which Pattern Fits You Best?

Click the pattern that most closely matches your experience to see targeted causes and strategies.

PATTERN A

Post-viral / Long COVID onset

"It started after an infection and never went away." Neuroinflammation, microclots, or viral persistence.

#01 Neuroinflammation · Long COVID · ME/CFS View Cause →
PATTERN B

Crash-recover-crash cycle

Fog after meals, sugar cravings, energy rollercoaster. Blood sugar instability affecting brain glucose.

#08 Glucose Dysregulation · Metabolic Issues View Cause →
PATTERN C

Gradual onset · Fatigue + weight gain · Cold intolerance

Thyroid and nutrient deficiency: under-tested, most fixable. Blood panel confirms in days.

#04 Thyroid · B12/Iron/D Deficiencies View Cause →
PATTERN D

Perimenopause · Cycle-linked fog · Age 38-55

Declining estradiol reduces serotonin, acetylcholine, cerebral glucose. Often misdiagnosed as depression.

#05 Menopause · PMDD · Testosterone View Cause →
PATTERN E

Bloating + fog · Food reactions · IBS symptoms

The gut-brain axis. The majority of serotonin is produced in the gut. Digestive symptoms + fog = start here.

#09 Gut Dysbiosis · SIBO · Histamine View Cause →
PATTERN F

Lifelong · Always been "spacey" · Worse with boredom

If fog has always been there (not acquired), ADHD is the most likely explanation.

#21 ADHD · Autistic Burnout · Digital Overload View Cause →

None of these fit? Scroll through all triggers below, sorted by clinical priority.

Symptom → Action Guide

Fog after medication
List every med + supplement. Search "[drug name] brain fog." Ask doctor about alternatives — never stop meds without asking.
Fog worst in morning / crashes after meals
Blood sugar instability. Eat ≥25g protein within 1hr of waking. Cut added sugar for 14 days. Request HbA1c.
Unrefreshed despite 7+ hours in bed
Ask for sleep study (polysomnography). Request RERAs scored — UARS causes fog with "normal" results.
Heart races / fog worsens on standing
POTS screen: Lie 5 min → take HR → stand → retake at 2, 5, 10 min. HR rise ≥30 bpm = show to doctor.
Lifelong focus difficulty (not recent onset)
Screen for adult ADHD. WHO ASRS-v1.1 screener (free, 6 questions). Score ≥4 Part A = formal evaluation.
History of tick bites / joint pain + fog
Lyme testing: ELISA + Western blot. Standard ELISA has limited sensitivity in early infection. Consider specialty lab if clinical suspicion is high.
Head injury / car accident / contact sports
Post-concussion syndrome. Request neuropsychological testing + vestibular assessment.
Female 40+ / hot flashes / cycle changes
Perimenopause. Request FSH, estradiol, progesterone. Discuss HRT — estrogen is neuroprotective.
Post-COVID or post-viral onset
Blood panel + hs-CRP. Consider low-dose naltrexone, omega-3 DHA 2g/day, creatine 5g/day.
Digestive symptoms alongside fog
Gut-brain axis. Request SIBO breath test + celiac panel. Try 14-day gluten/dairy elimination.
Fog improves with exercise but returns at rest
BDNF deficiency. Implement Aerobic BDNF Protocol — 150 min/week Zone 2 cardio.
High stress, anxiety, or trauma history
HPA axis dysfunction. Consider CBT or EMDR for trauma. Vagal tone exercises help.
Excessive screen time / doom-scrolling
Digital overload depletes prefrontal glucose. Implement Screen Boundaries protocol.
Water-damaged building / musty smells
Mold/biotoxin illness (CIRS). VCS test online (free, 5 min). Failed = investigate further.
Multiple amalgam (silver) fillings + unexplained fog
Mercury exposure. Request blood/urine mercury test. If elevated: SMART removal protocol.
Fog all day with no clear pattern
Get comprehensive blood panel. Rule out thyroid, iron, B12, vitamin D, and inflammation first.

Common Medication Culprits — Clinical Reference

Statins → Liver toxicity. Check liver function tests.
Beta-blockers, verapamil, alpha-blockers → Slow heart rate, low blood pressure.
Antihistamines (Benadryl, diphenhydramine) → Anticholinergic effects impair cognition.
Proton pump inhibitors (omeprazole, Nexium) → Mineral imbalance. Check ionogram.
Benzodiazepines → Excessive sedation. Cognitive effects can persist for weeks.
Paracetamol/Tylenol (high doses) → Liver toxicity. Check liver function tests.
View full medication causes guide →

Rare & Underdiagnosed Infections

Toxocara / Toxoplasma parasitosis — Especially with cats/dogs. Blood tests available.
Cat scratch disease (Bartonella) — May cause neuropsychiatric symptoms including irritability. Initial scratch often passes unnoticed.
Deep sinus / fungal sinus infection — Pain in upper jaw or base of skull. Requires ENT evaluation.
Denervated teeth on upper jaw — Roots without nerve can harbour chronic infections. Request dental X-ray.
Learn about Bartonella →

Multiple Matches? Stop and Escalate.

If you matched 3 or more branches above, do not attempt to self-manage with supplements. Request a comprehensive medical workup — ideally with a functional medicine or integrative medicine physician. Bring this decision tree to your appointment.

Finding the Right Doctor

If your doctor has dismissed your symptoms or run only basic labs, consider: Functional medicine physician (ifm.org), Naturopathic doctor (naturopathic.org), or Integrative medicine specialist. These practitioners investigate root causes rather than manage symptoms.

STEP 1

Self-Assessment

Score your severity (0-52)

STEP 2

Blood Panel Guide

18 biomarkers to request

STEP 3

The 14-Part Protocol

Evidence-based strategies

Still Not Sure?

Browse all 64 documented causes of brain fog, organized by category.

Browse All 64 Causes →

This information is for educational purposes only. Always consult with a qualified healthcare professional.