Archive · 7 Aug 2026
What happens to the body when you hold your breath
Everyone has held their breath, maybe in a pool or just for fun.
When you hold your breath, your body keeps using the oxygen it already has, like a car using fuel from its tank.
A waste gas called carbon dioxide slowly builds up in your body.
That growing carbon dioxide is what makes you feel like you really need to breathe, more than running out of oxygen does.
Your brain has special sensors that watch the carbon dioxide and send you a strong signal to take a breath.
If you hold your breath for a very long time, your heart may slow down and your body saves oxygen for important parts like your brain.
Eventually your brain gets less oxygen, and you may feel dizzy, confused, or even faint.
Breathing very fast before holding your breath can make you pass out suddenly underwater, which is very dangerous.
Doctors say it is safer to practise breath-holding on land, sitting down, with someone nearby.
Holding your breath as long as possible is not good for you, and you should never do it alone in water.
When breath-holding starts, the body uses oxygen already in the lungs and bloodstream while carbon dioxide gradually accumulates.
The urge to breathe is triggered primarily by rising carbon dioxide levels, not falling oxygen.
Heart rate may slow and blood vessels to the brain and heart dilate to maintain oxygen delivery; prolonged holding can impair concentration, judgment and coordination.
Hyperventilating before breath-holding lowers carbon dioxide and delays the urge to breathe, raising the risk of shallow water blackout and drowning even in healthy individuals.
Experts say controlled breath-holding can aid structured breathing practices, but pushing to the limit offers no health benefit, is dangerous for people with certain conditions, and should never be done alone in water.
- Who
- Dr Palleti Siva Karthik Reddy, Consultant Physician at Elite Care Clinic, provided the expert explanations.
- What
- Explains the physiological changes when holding breath as long as possible, including rising carbon dioxide, a slower heart rate, falling oxygen, and risks like shallow water blackout.
- When
- Not specified in the article.
- Where
- Not specified; the advice covers breath-holding on land and the dangers of doing it in water, such as during swimming.
- Why
- To help people understand normal body responses and warning signs, particularly those with heart or lung conditions or those breath-holding in water.
- Primary urge trigger
- Rising carbon dioxide levels, not falling oxygen
- First body responses
- Heart rate may slow; blood vessels to vital organs dilate
- Extreme effects
- Dizziness, confusion, impaired coordination, loss of consciousness
- Key danger
- Shallow water blackout, which can cause drowning even in healthy individuals
- People who should avoid
- Those with heart disease, uncontrolled high blood pressure, chronic lung conditions, epilepsy, or a history of fainting
- Safety advice
- Practise on land, seated or supervised; never alone in water
- Expert source
- Dr Palleti Siva Karthik Reddy, Consultant Physician, Elite Care Clinic