What is brain fog — and what's actually causing yours.
Hormones. Thyroid. Inflammation. Sleep. Metabolism. We test the dots most clinics don't.
Brain fog isn't a diagnosis on its own — it's a symptom of something else, and that something is almost always treatable. The hard part is figuring out which combination of hormonal, metabolic, thyroid, sleep, and inflammatory factors is driving yours. Mt. Baker Medical runs the workup standard primary care doesn't have time for — full thyroid with reverse T3, sex hormone panel, cortisol, inflammatory markers, micronutrients, methylation — and treats what the labs show, not whatever fits a fifteen-minute slot.
Services we use to treat brain fog.
PerimenopauseThe most common driver in women 40+NAD+ therapyCellular energy and post-viral recoveryHormone replacement therapyWhen perimenopause is the driverReady to investigate the root cause?
Thirty minutes with Dr. Scribner. No exam, no charge — just a conversation about what’s actually going on.
Book free consultation →What is brain fog — and what's actually causing yours.
Hormones. Thyroid. Inflammation. Sleep. Metabolism. We test the dots most clinics don't.
Brain fog isn't a diagnosis on its own — it's a symptom of something else, and that something is almost always treatable. The hard part is figuring out which combination of hormonal, metabolic, thyroid, sleep, and inflammatory factors is driving yours. Mt. Baker Medical runs the workup standard primary care doesn't have time for — full thyroid with reverse T3, sex hormone panel, cortisol, inflammatory markers, micronutrients, methylation — and treats what the labs show, not whatever fits a fifteen-minute slot.
What brain fog actually is.
Brain fog is the lay term for what neurologists call subjective cognitive dysfunction — the felt experience of being slower, foggier, and less mentally sharp than your baseline, usually without any change on a standard neurological exam or imaging. The lack of an obvious abnormality on routine tests is why primary care frequently dismisses it. The fact that it's real, persistent, and treatable is why the functional medicine workup matters. Brain fog is a downstream symptom, not a condition. Find the upstream driver and the fog usually lifts.
Six root causes — and the workup for each.
There is no single cause of brain fog. There is, however, a finite set of common drivers, and the differential is what the workup is for. Most patients turn out to have two or three of these working together.
Estradiol, progesterone, testosterone, and thyroid hormones all influence cognitive function directly. Perimenopause and menopause are the most common hormonal drivers of brain fog in women 40+; low testosterone is the male equivalent.
Full sex hormone panel with SHBG; full thyroid panel with reverse T3.
Insulin resistance, post-meal glucose spikes, and the inflammatory load of metabolic dysfunction all show up as cognitive symptoms before they show up on a standard fasting glucose. Continuous glucose monitor data often reveals what a fasting panel misses.
Fasting insulin, HbA1c, ApoB, lipid panel; CGM trial when indicated.
Chronic low-grade inflammation — from gut dysfunction, food sensitivities, mold or biotoxin exposure, or autoimmunity — drives cognitive symptoms via neuroinflammation. Often invisible on a routine CBC.
hsCRP, ferritin, full lipid panel, food sensitivity workup when warranted, mold panel for high-exposure patients.
Sleep apnea is under-diagnosed in women. Insufficient deep sleep degrades memory consolidation overnight. HPA axis dysregulation (cortisol rhythm off) blocks restorative sleep even when total hours look fine.
Sleep study referral when indicated; salivary cortisol rhythm.
B12, iron (ferritin), vitamin D, and magnesium deficiencies all cause cognitive symptoms. MTHFR variants and other methylation defects affect how nutrients get used.
B12, methylmalonic acid, ferritin, vitamin D, magnesium, optional MTHFR genotyping.
Long COVID cognitive sequelae, Hashimoto's flares, Lyme disease, and chronic viral reactivation can all present as brain fog. Worth investigating when the timeline matches.
Thyroid antibodies, autoimmune workup, chronic infection panel when history supports it.
Is your brain fog perimenopause?
If you're a woman in your late 30s through early 50s and brain fog showed up in the last one to three years without an obvious cause, perimenopause is the most likely driver. Estradiol is a profoundly important hormone for cognitive function — it affects neuronal energy metabolism, neurotransmitter regulation, and the brain's glucose use. As estradiol fluctuates and declines during perimenopause, cognitive symptoms often show up before periods become obviously irregular. The workup overlaps significantly with the perimenopause workup, and so does the treatment.
Read the full perimenopause workup →How to get rid of brain fog.
There is no single intervention for brain fog because there's no single cause. The protocol depends on what the workup shows. Common combinations: HRT if perimenopause is the driver; thyroid optimization if T3 is low; metabolic intervention — sometimes CGM, sometimes dietary, sometimes GLP-1 — if insulin resistance is the issue; sleep apnea evaluation if sleep architecture is off; targeted supplements for documented micronutrient deficiencies; NAD+ therapy as an adjunct when cellular energy is the framing and the other levers are already addressed.
In their own words.
Phrases patients use when they describe brain fog to us at the initial visit. They're not diagnostic — but they pattern-match.
I can't find the right word anymore. I'm forty-three and I'm staring at conversations like a tourist.
I've been doing my job for twenty years and now I have to write everything down. That's new.
Everyone said it was stress. Stress doesn't usually do this.
Patient-described, paraphrased for privacy. The patterns are real.
Common questions about brain fog.
What does brain fog feel like?
Most patients describe brain fog as a sense of mental slowness or thickness — like there's an extra processing step between thought and action, or like your brain is wading through something. Word-retrieval problems are common ('I know the word, I just can't find it'). Short-term memory drops — forgetting where you parked, what you walked into a room for, what someone just said. Reading comprehension suffers; you re-read paragraphs. Multitasking becomes harder. The felt experience is of operating below your normal baseline, often without an obvious reason.
What causes brain fog?
Brain fog is a downstream symptom with many possible upstream drivers. The most common in the patients we see: hormonal changes (perimenopause, low testosterone, thyroid dysfunction), metabolic dysfunction (insulin resistance, blood sugar swings), chronic inflammation, sleep disruption (sleep apnea, insufficient deep sleep), micronutrient deficiencies (B12, iron, vitamin D), and post-viral or autoimmune conditions (long COVID, Hashimoto's, Lyme). Most patients turn out to have two or three of these working together. The workup is designed to find which combination is yours.
How do I get rid of brain fog?
The protocol depends on what's driving it. If perimenopause is the upstream driver, HRT is often dramatic. If thyroid is low, optimizing T3 lifts the fog. If insulin resistance is the issue, metabolic intervention — sometimes CGM, sometimes dietary, sometimes GLP-1 — resolves it. If sleep architecture is off, fixing sleep fixes the cognition. Targeted supplements for documented deficiencies make a difference; generic 'brain fog supplements' usually don't. The shortcut is: run the labs, find the driver, treat the driver. No driver, no fix.
Does anything clear brain fog instantly?
Honestly: usually not. The Google search 'clear brain fog instantly' reflects the wish, not the reality. A short-term lift can come from sleep, hydration, caffeine, a meal that stabilizes blood sugar, or a hard walk — and those are worth doing. But persistent brain fog has a persistent driver, and only addressing the driver makes the change last. The patients who try every short-term fix and stay foggy are the ones who haven't yet gotten the workup that finds the upstream cause.
Brain fog vs early dementia — when should I worry?
This is one of the most common fears we hear at the initial visit, and the honest answer is that the brain fog associated with perimenopause, low testosterone, thyroid dysfunction, or metabolic issues is reversible and not dementia. Dementia presents differently: progressive worsening over months to years, deficits visible to others before to the patient, problems with familiar tasks (paying bills, following recipes), and changes on cognitive testing. Reversible brain fog tends to fluctuate, often coexists with other symptoms (sleep, mood, hormonal), and improves when the upstream issue is treated. If concerns persist, formal cognitive testing through a neurologist is appropriate. Most patients with reversible brain fog do not need that level of workup, but it's available when the picture warrants it.
Is brain fog a sign of perimenopause?
Often, yes — particularly if you're a woman in your late 30s through early 50s, the fog came on in the last 1–3 years, and other perimenopause symptoms (sleep changes, mood shifts, weight gain, cycle changes) are showing up alongside it. Estradiol is critical for cognitive function, and as it fluctuates and declines during perimenopause, cognitive symptoms commonly appear before periods become obviously irregular. The same workup that confirms perimenopause confirms whether it's the brain fog driver — and HRT, when indicated, often resolves the fog within weeks.
Ready to figure out what's actually causing it?
Thirty minutes with Dr. Scribner — no exam, no commitment, no charge. We talk through your symptoms, your timeline, and the workup that would find the upstream driver.