I Found (Another Reason) What Was Causing My Brain Fog. It Was My Fuel.
Introduction
You read the same paragraph three times. Still nothing.
You walk into a room and forget why. Again.
You sit in meetings, nodding, while your brain is somewhere else entirely.
Has been for years.
I know this feeling intimately. Brain fog wasn't a phase for me. It was just... life.
I'd tried everything. Supplements. Sleep adjustments. Meditation.
I'd honestly accepted that this was just how my brain worked. Some people think clearly.
I wasn't one of them.Then I started measuring what was actually happening inside my body.
The Number That Finally Made Sense
I bought a glucose meter almost as a joke, after a doctor’s visit for something unrelated. Another thing to try. Another thing that probably would not work.
My first fasting reading: 6.3 mmol/L.
I had no idea what that meant, so I looked it up. Prediabetic range.
I was not diabetic. I was not overweight.
But that number finally explained something I had felt for years without words:
My brain was starving while my blood was flooded with fuel it could not use properly.
Two weeks later, after changing how I ate, I woke up at 4.4 mmol/L.
For the first time in longer than I can remember, I felt clear.
Not caffeinated‑clear.
Not “good day” clear.
Actually clear.
Why Nobody Told Me This Sooner
Here is what someone should have explained to me years ago:
Your brain can run on two main fuels: glucose (sugar) and ketones (from fat).
Glucose is a nightmare for consistency.
You eat. Sugar spikes. Insulin crashes it down. Your energy follows.
Ketones work differently.
Steady. Constant. No peaks. No crashes. Just clean, reliable power.
I had heard of keto before and dismissed it as a weight‑loss fad. Because it "keto" was everywhere.
It never occurred to me it might fix the one thing I actually cared about: my ability to think.
What Actually Happened When I Tried It
I am not going to pretend it was smooth.
It was not.
Days 1–5: Worse Before Better
I cut carbs hard: meat, eggs, butter, and not much else.
My blood sugar dropped to 4.4 mmol/L. On paper, perfect.
But I felt like garbage. Groggy. Heavy.
Like my body had forgotten how to function. Classic “keto flu”.
Here is what I wish someone had told me: the grogginess is not about energy, it is about salt.
When you cut carbs, your kidneys flush sodium like crazy. A teaspoon of salt in water can turn the lights back on.
Days 5–7: The Fake Breakthrough
Then I felt amazing. Sharp. Energized.
I told myself I had finally cracked it. I had not.
Most of that “clarity” was adrenaline and cortisol from the stress of the transition, not calm focus.
It felt like focus. It was actually survival mode.
Little by little, my blood sugar bounced between 5.2 and 5.7 mmol/L.
I almost quit. Figured it was another dead end.
Then I learned this is completely normal.
Your muscles start rejecting glucose to save it for your brain, so blood sugar can float a bit higher during the transition.
What I Learned From Tracking
Salt
I tested my blood sugar constantly for two weeks: morning, after meals, after workouts.
Whenever I started to feel groggy or foggy, salt and water helped more than anything else.
Blood work later showed I was low in sodium and potassium, so this made sense.
A glass of water with salt usually made me feel better within 15–30 minutes.
Sleep
Sleep destroys everything when it is bad.
One rough night and my morning sugar jumped from 4.9 to 5.7, without eating anything.
Poor sleep can increase insulin resistance and raise blood sugar because cortisol spikes and the liver dumps sugar.
Half of what I blamed on diet over the years was probably just terrible sleep.
Move
Movement is non‑negotiable.
I skipped workouts for a week because I felt weak from being sick. My blood sugar climbed back to 6.0 and the fog returned.
A simple 20‑minute walk now reliably drops my reading by 0.3–0.5 mmol and clears my head.
The Trap That Almost Made Me Quit
I got a minor cold. Sore throat. Nothing serious. Blood sugar shot back up 5.9 mmol/L. (Again).
Hadn't touched carbs in 10 days. I thought I'd ruined everything.
I did some research and I think this is what is happening:
When fighting anything - even a mild cold - body deliberately raises blood sugar to fuel the fight.
You become temporarily "diabetic" to power your immune system.
It's your body prioritizing survival. So I think I have to wait until I am healthy and I bet that clarify will return.
What Worked For Me
This is not medical advice. It is simply what actually helped me.
Phase 1: Survive The Switch
- Carbs under 20 g daily: meat, eggs, butter, leafy greens.
- Salt everything. Drink salted water when groggy, but do not overdo it.
- Expect to feel worse before you feel better. This is the transition, not failure.
- Sleep 7+ hours. Magnesium before bed helped me wind down.
Phase 2: Ride Out The Weirdness
- Your body is stressed and cortisol is higher for a while.
- Keep moving. Walking counts. Just do something every day.
- Eat when you are actually hungry. Do not force long fasts yet or eat from habit (like automatic breakfast).
Phase 3: When It Finally Clicks
- This is when the real shift happens.
- Energy becomes steady instead of spiky.
- You sometimes forget to eat and do not crash.
- The fog becomes rare instead of constant.
What I Know Now
Brain fog is a symptom. Symptoms have causes. The hard part is finding yours.
For me, after years of assuming I was just built this way, one big cause was unstable blood sugar.
With brain fog it is almost never one thing, but a pile of small things that add up to feeling awful.
The cheap glucose meter I bought as a joke ended up being the key, because it gave me data instead of guesses.
If you have been foggy for years and nothing has worked, spend 20 dollars on a basic glucose meter.
Test your blood sugar for two weeks and see what your numbers are telling you.
Interested in learning more?
