Last updated: October 2026
Fight or flight is your body’s automatic stress response. Adrenaline and cortisol speed up your heart and breathing and send blood to your muscles so you can act fast. It’s helpful in real danger, but it can switch on with everyday stress or anxiety too. Slow breathing, with long out-breaths, and movement help it settle.
Below: what happens in your body, the symptoms and why they happen, fight, flight, freeze and fawn, how it differs from “rest and digest”, why it can get stuck, and how to calm it.
The short version: fight or flight is an alarm, not a fault. The feelings are unpleasant but not dangerous in themselves, and your body is built to switch the alarm off again. The trick is giving it the signal that you’re safe.
What is the fight or flight response?
The fight or flight response (sometimes called fight or flight mode) is how your body prepares to deal with a threat: to face it, or to get away from it. It’s run by your autonomic nervous system, the part that works without you having to think about it.
It starts in the brain. The amygdala, which processes emotion, spots possible danger and alerts the hypothalamus, your brain’s command centre. That switches on the sympathetic nervous system, the body’s accelerator. This happens so quickly that your body can react before you’ve fully registered what you’ve seen, which is why you can jump back from a car before you consciously “see” it.
Two systems then work together. The fast one is the sympathetic nerves and the adrenal glands, which release adrenaline within seconds. The slower one is the HPA axis (hypothalamus, pituitary and adrenal glands), which releases cortisol to keep you on alert for longer. Medical reviews describe the response as adaptive: it exists to protect you.
Children have the same alarm system. If a child’s worries, outbursts or shutdowns are frequent, talk to your GP or their school.
Fight or flight hormones
| Hormone | Where it comes from | What it does |
|---|---|---|
| Adrenaline (epinephrine) | Adrenal glands, within seconds | Faster heart, quicker breathing, wider airways, releases stored sugar and fat for energy |
| Noradrenaline (norepinephrine) | Sympathetic nerves and adrenal glands | Raises alertness and blood pressure, works alongside adrenaline |
| Cortisol | Adrenal glands, via the HPA axis, over minutes | Keeps the alarm running and keeps energy available; falls again when the threat passes |
Cortisol is the one people worry about most. A short rise is normal and healthy. Problems come when it stays high for weeks. See how to lower cortisol naturally.
Fight or flight symptoms
Every symptom has a purpose: it gets you ready to move. That’s why they can feel so strong, even when there’s nothing to run from.
| What you notice | Why it happens |
|---|---|
| Racing or pounding heart | Pumps more blood to your muscles and brain |
| Fast, shallow breathing | Takes in more oxygen; breathing too fast can leave you light-headed |
| Tight chest | Tense chest muscles and fast breathing |
| Dizziness | Changes in breathing and blood flow |
| Butterflies, nausea, needing the loo | Digestion is put on hold while blood goes to your muscles |
| Dry mouth | Saliva slows down along with digestion |
| Sweating | Cools you down in case you need to run or fight |
| Shaking, tense muscles | Muscles primed for action, plus extra adrenaline |
| Sharper senses, feeling on edge | Your brain is scanning for danger |
| Racing thoughts, hard to focus | Attention narrows onto the threat |
For more on individual symptoms, see anxiety chest pain, anxiety stomach and heart palpitations at night. Our guide to stress symptoms covers the longer-term signs.
Fight, flight, freeze or fawn
Fight and flight aren’t the only options. Researchers describe a “defence cascade” of automatic responses to threat:
- Fight: facing the threat. Irritability, anger, a clenched jaw.
- Flight: getting away. Restlessness, wanting to leave, avoiding things.
- Freeze: going still. A 2015 review describes freezing as fight or flight “put on hold”. People may feel stuck, spaced out, disconnected from their body or unable to speak.
- Fawn: trying to appease or please the person you feel threatened by.
Freeze is well described in the research, along with deeper shutdown states. Fawn is different. The term was coined by a psychotherapist in a 2013 book on complex trauma, and there isn’t much research on it yet. It’s a useful way to describe people-pleasing that comes from fear, but it isn’t part of the scientific defence cascade.
Fight or flight vs rest and digest
Your autonomic nervous system has two main branches. The sympathetic branch is the accelerator; the parasympathetic branch is the brake, which calms you down once the danger has passed. Much of it runs through the vagus nerve.
| Fight or flight (sympathetic) | Rest and digest (parasympathetic) | |
|---|---|---|
| Job | Gets you ready for action | Recovery, digestion, repair |
| Heart rate | Faster | Slower |
| Breathing | Quick, shallow | Slow, deeper |
| Digestion | Paused | Active |
| Muscles | Tense | Relaxed |
| Mind | Alert, scanning for danger | Calmer, able to switch off and sleep |
Both are healthy. Being able to move between them is what people mean by nervous system regulation.
When fight or flight gets stuck
The alarm is meant to be short. When the threat passes, cortisol falls and the brake takes over. But modern stressors (an inbox, money worries, a difficult relationship) don’t go away when you run, so the alarm can keep sounding at a low level for weeks. Medical reviews link long-term stress with anxiety, depression and heart disease.
It can show up in a few ways:
- Chronic stress: feeling wired but tired, poor sleep, tense shoulders, stomach upsets.
- Generalised anxiety disorder (GAD): the NHS describes ongoing worry that is difficult to control, with physical signs such as tension, tiredness, dizziness and a noticeable heartbeat. See anxiety symptoms.
- Panic attacks: a sudden, intense surge of fight or flight, often “for no reason”. The NHS says most last between 5 and 20 minutes, and while frightening, they aren’t dangerous. See how to stop a panic attack.
How to calm fight or flight
In the moment
- Breathe out for longer than you breathe in. Long out-breaths are one of the quickest ways to press the brake. In a Stanford trial, 5 minutes a day of “cyclic sighing” (a breath in, a second short sip of air, then a long slow breath out) improved mood and slowed breathing more than mindfulness meditation. Try 4-7-8 breathing or box breathing too.
- Name it. Telling yourself “this is my alarm going off, it will pass” takes away some of the fear that keeps it going.
- Ground yourself. The 5-4-3-2-1 method pulls your attention out of the threat and back into the room. See grounding techniques.
- Use the energy. Your body has just been primed to move, so a brisk walk or shaking out your arms and legs can help it settle. See somatic exercises.
Day to day
- Move most days. Regular exercise is on the NHS self-help list for panic, and a brisk walk deepens breathing and eases muscle tension.
- Protect your sleep. Lack of sleep is itself a stressor on the body, so a tired body reacts more easily.
- Watch the caffeine. The NHS suggests cutting back on caffeine, alcohol and sugar if you get panic attacks.
- Talk to people you trust. Close relationships help people cope with ongoing stress, and saying it out loud often takes some of the charge out of it.
One contrast worth knowing: Wim Hof breathing does the opposite of calming. Its rapid breathing and breath holds deliberately trigger the stress response; a 2014 study found trained volunteers had “profoundly increased” adrenaline levels. That’s fine for some people, but it isn’t the tool to reach for when you’re already in fight or flight.
Food and supplements play a small, supporting role. Magnesium contributes to the normal functioning of the nervous system and to normal psychological function. Our Magnesium Glycinate Sleep Complex is a caffeine-free evening drink with magnesium bisglycinate and citrate, glycine and L-theanine, and many people find it a useful wind-down cue. Some people take our Flow CBD Oil, with ashwagandha and maca, as part of their day. CBD isn’t a treatment for anxiety. The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication. Our products are for adults only, and we don’t recommend them during pregnancy or breastfeeding.
When to see a GP
See a GP if fight or flight feelings are frequent, last for weeks, stop you doing everyday things or keep you awake, or if you think you might have GAD or panic disorder. Treatments such as CBT work well, and adults in England can refer themselves to NHS Talking Therapies. If you’ve been signed off work with stress, our guide explains how it works in the UK.
Get urgent help if you have chest pain that doesn’t go away, pain that spreads to your arm, neck, jaw or back, or chest pain with sweating, sickness or breathlessness: call 999. Don’t assume it’s anxiety. If you feel unable to cope, call NHS 111 or Samaritans free on 116 123.
For simple ways to switch out of fight or flight in the moment, see how to calm down fast.
FAQs
What is the fight or flight response?
Your body’s automatic reaction to a threat. Adrenaline and cortisol raise your heart rate, speed up your breathing and send blood to your muscles so you can face danger or escape it.
What does fight or flight feel like?
A racing heart, fast breathing, a tight chest, butterflies or nausea, sweating, shaking, a dry mouth and feeling on edge. It can feel frightening, but the symptoms aren’t dangerous in themselves.
How long does fight or flight last?
The adrenaline surge is fast and usually fades within minutes once you feel safe, and cortisol falls when the threat passes. Panic attacks usually last 5 to 20 minutes. Ongoing stress can keep you on alert for much longer.
Why am I in fight or flight for no reason?
Your alarm can be set off by stress, worry, tiredness, caffeine or a past experience, even when there’s no danger in front of you. If it happens often, it may be anxiety or panic disorder, which are treatable, so see a GP.
How do I get out of fight or flight mode quickly?
Breathe out for longer than you breathe in for a minute or two, remind yourself it will pass, then ground yourself in the room or go for a brisk walk.
What is the difference between fight or flight and rest and digest?
Fight or flight (sympathetic) gets you ready for action. Rest and digest (parasympathetic) slows your heart and breathing and restarts digestion so you can recover.
Sources
- Chu B et al (2024). Physiology, Stress Reaction. StatPearls.
- Harvard Health Publishing. Understanding the stress response.
- Kozlowska K et al (2015). Fear and the defense cascade: clinical implications and management. Harvard Review of Psychiatry.
- The Conversation. What is fawning? How is it related to trauma and the fight or flight response?
- Balban MY et al (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine.
- Kox M et al (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. PNAS.
- NHS. Panic disorder and Generalised anxiety disorder (GAD).
- NHS. Chest pain.
This guide is general information, not medical advice. Evopure makes the Magnesium Glycinate Sleep Complex and Flow CBD Oil.
