BF 2: The 4 Brain Fog Causes & Why Your Brain is So Foggy?

Foggy hike in Sydney's Blue Mountains

You know that feeling—you walk into a room, stand there for a moment, and wonder what on earth you came in to get. Or you’re mid-conversation, and the perfect word is on the tip of your tongue but won't come. If that sounds familiar, you’re not alone. Brain fog is one of the most common (and frustrating) symptoms of perimenopause and menopause and can be grouped into different types based on what the major factor causing symptoms is.

Why Identifying Your Brain Fog Causes Matters

While brain fog feels similar across the board (forgetfulness, slow thinking, mental exhaustion), the root cause(s) can be different for everyone. That’s why tackling brain fog requires more than a one-size-fits-all approach—what works for one person might not help another.

Research suggests that brain fog in midlife can stem from various biological factors, including hormonal shifts, blood sugar regulation, stress and sleep disturbances, and gut health. Understanding which factor is most influencing your brain fog is key to finding the right solutions.

Let’s break them down:

1) The Hormonal Shift Brain Fog

What it feels like:

• Struggling to find words mid-sentence.

• Forgetting things you normally remember with ease.

• A sluggish, foggy brain that seems to come and go unpredictably.

What’s causing it:

As estrogen and progesterone fluctuate and decline, so does your brain’s ability to process information efficiently. These hormones support memory, focus, and mental clarity by regulating neurotransmitters like acetylcholine, a key player in cognitive function. When levels drop, so does mental sharpness.

2) The Blood Sugar Brain Fog

What it feels like:

• Feeling mentally sluggish after meals.

• Experiencing an afternoon energy crash that makes focus impossible.

• Craving sugar or carbs when you need to concentrate.

What’s causing it:

Your brain relies on a steady stream of glucose for energy, but during perimenopause, shifts in insulin sensitivity can lead to blood sugar fluctuations. When your brain isn’t getting the steady fuel supply, brain fog kicks in.

Note: This does not mean you can eat a pile of biscuits— what you eat matters just as much as when you eat.

3) The Stressed & Sleepless Brain Fog

What it feels like:

• Feeling wired but exhausted at the same time.

• Losing focus under stress or when overwhelmed.

• Waking in the middle of the night, unable to fall back asleep.

What’s causing it:

When stress levels rise, so does cortisol, your body's primary stress hormone. Chronic cortisol spikes disrupt sleep, leading to exhaustion and poor focus.Sleep is crucial for cognitive function, particularly during deep sleep, when the brain "detoxifies" itself. If stress and sleep disruptions become a pattern, the brain stays in high-alert mode, impairing memory, focus, and emotional regulation.

4) The Gut Microbiome Brain Fog

What it feels like:

• Constant brain fog that never really lifts.

• Bloating, irregular digestion, or unexplained gut discomfort.

• Feeling mentally sluggish even after a full night’s sleep.

What’s causing it:

Your gut and brain are deeply connected, and the gut microbiome plays a key role in cognitive function by producing neurotransmitters. Some gut bacteria act like tiny factories, making compounds that support memory, focus, and mood.

However, during perimenopause and menopause, hormonal fluctuations disrupt the gut microbiome. This can slow or stop the production of brain-supporting neurotransmitters, increase inflammation, and reduce nutrient absorption—all factors that contribute to brain fog.

What’s Next?

Not all brain fog is the same. Identifying your type is the first step toward finding what might work best for you.

Take the FREE Brain Fog Quiz → Find Out Your Brain Fog Type

This quiz will help you pinpoint:

·      Which type of brain fog you’re experiencing.

·      What could be triggering it.

·      The next step toward clearer thinking.

Up Next: See BF 3: Can Brain Fog Really Be Improved? What Science Says in Related Posts below.

Missed the previous post? See BF 1: Brain Fog in Perimenopause & Menopause: What It Is (and What It Isn’t) in Related Posts Below.

Disclaimer: Everyone’s experience with perimenopause and menopause is different. This post is for informational purposes only and is not a substitute for medical advice. Learn more here.