Is holding your breath bad for you?
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Short, comfortable holds while you’re sitting down are fine, like the four seconds in box breathing or a calm hold after a normal breath out. Long holds after fast breathing are the risky kind. They can make you black out without warning, which is why they never belong in or near water.
Holding your breath feels like it should be self-limiting. You’ll gasp before anything bad happens. That’s true when you start from normal breathing. It stops being true when you breathe hard first, because the alarm that makes you gasp runs on carbon dioxide, and you’ve just blown most of it away.
What we’d do
Keep everyday holds short and comfortable, and stop at the first clear urge to breathe. Never do long holds, or any hold after fast breathing, in a pool, a bath, the sea, or a car. Never hyperventilate before swimming underwater. If holds make you anxious, use a pattern without them.
Why the alarm can fail
Your urge to breathe is driven mostly by rising carbon dioxide. Breathe normally and hold, and carbon dioxide builds up fast enough to make you breathe long before oxygen runs low. Breathe hard for a minute first, and carbon dioxide starts so low that oxygen can fall a long way before the urge kicks in.
It’s like taking the battery out of a smoke alarm. The fire still burns, you just don’t get the warning. In a 2014 study of Wim Hof breathing, the trained men’s blood oxygen dipped to around 50 percent at times. Most people sit at 95 to 100.
What happens in water
A CDC report looked at New York State from 1988 to 2011 and found 16 people who blacked out underwater from breath holding. Four died. All four who died were advanced or expert swimmers aged 17 to 22, and all four had hyperventilated on purpose before going under. Fifteen of the 16 cases happened in pools.
The report’s explanation is the smoke alarm problem. Hyperventilating lowers carbon dioxide and delays the signal to surface, and the blackout comes from the drop in oxygen.
Holds that are fine
| Hold | Where it shows up | Risk |
|---|---|---|
| 4 seconds, full or empty | Box breathing | Low, sitting down |
| 7 seconds, full | 4-7-8 | Low, sitting or lying down. Shorten it if you get lightheaded |
| A comfortable hold after a normal breath out | The BOLT test | Low. You stop at the first clear urge |
| Holding until you can’t, after 30 fast breaths | Wim Hof rounds | Can black you out. Only lying or sitting, never in water or a car |
| Any hold after hyperventilating, underwater | Breath-hold games and training in pools | Can kill. Never |
The comfortable hold as a number
A short, calm hold after a normal breath out is the basis of the BOLT test. You time it and stop at the first clear urge to breathe or swallow. A 2006 review of breath holding describes it as easy to time but highly variable, and the breakpoint isn’t set by blood gases alone. Gyroscope’s coaching bands for it are in what’s a good BOLT score. A longer hold doesn’t mean you’re fitter, as the myth a long breath hold means you’re fit explains.
What happens when you hold your breath? has the breakpoint, the diving response and the numbers.
6 sources
- Boyd C et al., Notes from the field: hazardous breath-holding behaviors, New York, 1988 to 2011, MMWR, 2015cdc.gov
- Parkes MJ, Breath-holding and its breakpoint, Experimental Physiology, 2006pubmed.ncbi.nlm.nih.gov
- Gyroscope, BOLT score benchmarkgyrosco.pe
- Wim Hof Method, Safety warnings, checked 2026-11-14wimhofmethod.com
- Kox M et al., Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans, PNAS, 2014pmc.ncbi.nlm.nih.gov
- Cleveland Clinic, Blood oxygen levelmy.clevelandclinic.org
