Adrenaline: what it does during stress

Adrenaline (also called epinephrine) is a hormone your adrenal glands release within seconds of a perceived threat or stressor. It speeds up your heart rate, raises blood pressure, opens your airways, and pushes stored glucose into your blood for quick energy. That’s the biology behind the fight-or-flight response, and the hormone itself clears from your blood again within minutes.

Where does adrenaline come from?

Adrenaline is made in your adrenal medulla, the inner core of your adrenal glands, which sit on top of your kidneys. Specialized cells there called chromaffin cells produce a mix that’s roughly 80% adrenaline and 20% noradrenaline, according to Cleveland Clinic.

The release is triggered by your sympathetic nervous system. Once your brain flags a threat, a signal travels down your spinal cord to your adrenal glands. Adrenaline reaches your bloodstream within seconds, according to a 2018 review in Frontiers in Behavioral Neuroscience.

What does adrenaline actually do in your body?

Once it’s circulating, adrenaline works fast. Cleveland Clinic describes effects like a faster heart rate, higher blood pressure, wider airways, and glucose released into your blood for quick fuel. Together, these changes are the physical core of fight-or-flight: your body redirecting resources toward whatever feels urgent in the moment.

Because these effects are so reliable and fast, doctors also use a manufactured version of adrenaline as emergency medicine. An epinephrine auto-injector is the standard first-line treatment for severe allergic reactions, per Cleveland Clinic.

How long does an adrenaline surge last?

Not as long as it feels like in the moment. The hormone itself has a short half-life and clears from your blood within minutes, per StatPearls. But some effects fade more slowly: Cleveland Clinic notes a faster heart rate can take up to about an hour to fully settle. Cortisol and blood sugar work their way back down on a similar timeline.

Our guide to recovering after an adrenaline dump walks through what helps in that window, and why adrenaline makes you shake covers one common effect people notice most.

Where does bilateral stimulation fit in?

Adrenaline and cortisol are two halves of the same stress response: adrenaline is the fast spike, cortisol is the slower follow-through. Practices that calm your nervous system tend to touch both. Bilateral stimulation, the left-right rhythm at the center of EMDR, is one option people use as a regular practice for settling an activated stress response. EmEase, a self-guided EMDR app, offers a guided version of this practice at app.emease.com.

Frequently asked questions

What is adrenaline in simple terms?

Adrenaline, also called epinephrine, is a hormone your adrenal glands release within seconds of a perceived threat. It speeds your heart rate, raises blood pressure, opens your airways, and releases stored glucose for quick energy. It's the biological engine behind the fight-or-flight response, and it clears from your blood again within minutes.

What triggers an adrenaline release?

Anything your brain reads as a threat or urgent demand: real danger, a near-miss, a stressful memory, or a big presentation. Your sympathetic nervous system fires a signal down your spinal cord to your adrenal glands, which release adrenaline into your bloodstream within seconds. The trigger doesn't need to be a genuine emergency for the response to fire.

What are the main physical effects of adrenaline?

Cleveland Clinic describes effects like a faster heart rate, higher blood pressure, wider airways, and glucose released into your bloodstream for quick fuel. These changes happen within seconds and work together to redirect your body's resources toward handling whatever feels urgent, whether or not real danger is involved.

How long does an adrenaline rush actually last?

The hormone itself clears from your blood within minutes, thanks to a short half-life. But the effects it triggers, like a faster heart rate and elevated blood sugar, can take up to about an hour to fully settle as cortisol works its way back down too. That gap is most of what people mean by an adrenaline 'crash.'

Is adrenaline the same thing as cortisol?

No. They're partners, not the same hormone. Adrenaline is the fast-acting spike that hits within seconds and clears within minutes; cortisol is the slower stress hormone that follows, staying elevated for longer and handling more of the sustained response. Most stressful moments involve both working together, not just one.

Is adrenaline ever used as an actual medicine?

Yes. A manufactured version of adrenaline, epinephrine, is the standard first-line treatment for severe allergic reactions, given through an auto-injector. It works by tightening blood vessels, opening airways, and raising blood pressure, the same core effects your body produces naturally during a stress response, just delivered on purpose in an emergency.

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