Low Cortisol, High Stress: How Fight-or-Flight Really Works

I want to start with a question that comes up all the time.

“If cortisol is low, how can the body still be stressed?”

It makes total sense to think that way. We hear over and over that cortisol is the stress hormone. So if cortisol is low, shouldn’t that mean the body is calm, rested, and out of fight-or-flight mode?

Not exactly.

In this post, we’re going to clear up why low cortisol does not automatically mean low stress, and how the body can stay in fight-or-flight even when cortisol levels drop. I’ll walk you through what’s happening, so if you’ve ever felt stressed in your body but confused by your labs, this will help it all make a lot more sense.

? Before we get started:
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The Confusion Around Cortisol and Stress

Here’s where most people get stuck.

• They learn that high cortisol equals stress.
• They learn that stress can suppress the thyroid.
• Then they hear that later stages of adrenal fatigue mean low cortisol.

So the logical conclusion is, “If cortisol is low, the body must not be stressed anymore.”

The body can absolutely still be in fight or flight while producing low levels of cortisol.

And yes, that sounds confusing at first, but stay with me.

What Happens During Long-Term Stress

The body usually does not go straight to low cortisol.

First, the HPA axis ramps cortisol up. Sometimes for weeks, months, and even years.

During that time:

• Cortisol stays elevated
• The body stays under constant stress
• Over time, the thyroid can begin to slow down because the body is lowering its metabolic rate

Eventually, after being pushed for long enough, cortisol production can drop. That crash is what many people refer to as adrenal-based fatigue.

So, low cortisol is not the absence of stress. It is often the result of too much stress for too long.

Related:
10 Hidden Signs of High Cortisol (And How to Fix It)

The HPA Axis Can Change How Cortisol Is Produced

This is what’s referred to as HPA axis dysfunction.

It means the communication between the brain and the adrenals changes. The hypothalamus, pituitary, and adrenal glands stop signaling the body to produce as much cortisol.

That does not mean the stress response is turned off.

It simply means cortisol output is lower.

A clear example of this is Addison’s disease. It’s a rare condition and not something I would ever wish on anyone. People with Addison’s disease can have very low cortisol and still experience a stress response, which shows that cortisol alone is not what controls fight-or-flight.

Cortisol Is Not What Starts Fight-or-Flight

Cortisol does not initiate fight-or-flight.

It’s described as “second in the parade.”

Cortisol’s role is to support the body after the stress response has already started. It helps the body meet the energy demands of the fight-or-flight response.

Cortisol:

• Helps provide energy during stress
• Signals the body to break down liver glycogen
• Makes more glucose available in the bloodstream
• Has short-term anti-inflammatory effects

What Starts Fight-or-Flight?

This is where adrenaline and norepinephrine matter most.

These hormones are responsible for triggering the body’s fight-or-flight response. They activate the nervous system and create that “revved up” feeling people often describe.

Because of this, the fight-or-flight response can remain active even when cortisol output is low.

So when we go back to the original assumption, “If cortisol is low, the body must not be stressed,” it becomes clear why that doesn’t hold up.

Cortisol supports the stress response once it’s already underway, but it isn’t what turns it on.

That’s why someone can be producing less cortisol and still feel stuck in a stress state, especially in later stages of adrenal-based fatigue.

Quick Recap

✅ Low cortisol does not mean the body is calm
✅ The body can still be in fight-or-flight with low cortisol
✅ Long-term stress can lead to a cortisol crash after extended high output
✅ Cortisol supports the stress response but does not start it
✅ Adrenaline and norepinephrine are what trigger fight-or-flight

Final Thoughts

If you’ve been confused by your labs, your symptoms, or the mixed messages you’ve received about stress, you’re not alone.

It’s easy to assume that low cortisol means the body is finally resting. But the nervous system can still be stuck in a stress response even when cortisol output is low. What that means is that your body has adapted after being under pressure for a long time.

Understanding this can be a big relief. It helps explain why you might still feel on edge, wired, or exhausted even when your numbers say you shouldn’t.

Now I’d love to hear from you! Have you ever felt stressed, wired, or on edge even when your labs said everything looked “low” or “normal”? Let me know in the comments below.

? Still dealing with bloating, fatigue, or gut issues, no matter what you try?

If you’ve been chasing symptoms and nothing seems to stick, it’s time to look deeper. I’d love to help you uncover the root cause of your digestive + hormone issues so you can finally get the answers you’ve been looking for.

? To get started, learn how private coaching and functional lab testing can help you.

Additional Resources

• 10 Hidden Signs of High Cortisol (And How to Fix It)
• When is the Best Time to Test Cortisol: Morning or Night?
• 8 Best Foods That Lower Cortisol and Calm Stress
• 7 Simple Activities That Naturally Lower Cortisol and Improve Mood
• 8 Hidden Symptoms of Adrenal Fatigue Most People Miss

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