Is cold plunging safe? Who should avoid it, and why
Cold water raises your breathing, heart rate and blood pressure within seconds. Who the health sources say should avoid a plunge, who should ask a clinician first, the limits they print, and which signs mean call 911.
Short answer: Not for everyone, and we found no count of how often plunges hurt people. Harvard Health says a plunge isn’t advisable for anyone who has had cardiovascular disease, and that people with a heart rhythm disorder, peripheral artery disease or Raynaud’s should avoid it. Cleveland Clinic adds high blood pressure, diabetes, pregnancy, peripheral neuropathy and poor circulation as reasons to ask your provider first. For everyone else its limits are a minute or two as a beginner, never longer than five minutes and never below 40°F. Never go alone or after alcohol. Call 911 for confusion, slurred speech, chest pain or shivering you cannot control.
This guide is general information, not medical advice. If you have a heart, lung, blood or circulation condition, your own clinician’s advice comes first.
We did not visit or test any venue or tub. Everything here comes from the health bodies, makers and studies named, read between Oct. 25 and Nov. 3, 2026.
When to call 911 during or after a cold plunge
Being cold and shivering with a clear head is what the 2024 American Heart Association and American Red Cross first aid guidelines call simple cold stress. Get out, warm up and keep someone with you. The signs below are different.
| Sign | Who says so | What to do |
|---|---|---|
| Goes under, stops breathing or cannot be woken | MedlinePlus on non-fatal drowning | Call 911. If breathing has stopped, start rescue breaths as soon as you can, and CPR once on land if needed. Anyone who needed this goes to the hospital, even if they seem fine |
| Confusion, mumbling speech, unable to stay awake, stumbling, or unable to help take off wet clothes | The 2024 first aid guidelines, as potential signs of life-threatening hypothermia | Call 911 and keep warming the person |
| Shivering that cannot be controlled, or shivering that stops while the person is still cold | MedlinePlus on hypothermia, which says to call 911 anytime you suspect it | Call 911 |
| Slurred speech, fumbling hands, memory loss or unusual tiredness | CDC’s warning signs of hypothermia | Call 911 |
| Rigid muscles, blue skin or an erratic heartbeat | Plunge’s safety notice, which says to stop and call 911 | Call 911 |
| Crushing or squeezing pressure in the chest, pain spreading to the jaw or left arm, or chest pain with a racing heart or shortness of breath | MedlinePlus on chest pain | Call 911 |
| A faint with no recovery within a couple of minutes, or with chest pain or a pounding or irregular heartbeat | MedlinePlus on fainting | Call 911 |
| Hives with fainting, wheezing or shortness of breath | Cleveland Clinic on cold urticaria, which calls these reactions very rare; MedlinePlus says to call 911 for anaphylaxis | Call 911 |
CDC warns that low body temperature affects the brain, so a person may not know it is happening. That is why someone else needs to be watching.
Our guide on what to do after a cold plunge covers rewarming and fainting after you get out.
What is the cold shock response?
It is your body’s automatic reaction to sudden cold water on the skin. American Heart Association News describes a sudden, rapid increase in breathing, heart rate and blood pressure, and says it can cause a person to drown within seconds if they gasp with their head under water.
Harvard Health says the shock sends adrenaline and norepinephrine into the bloodstream and narrows the blood vessels of the skin, which shifts more blood to the chest and taxes the heart.
The fast breathing is a danger of its own. Cleveland Clinic warns it can lead to dizziness or fainting, especially while in the water.
The National Center for Cold Water Safety, a safety group focused on paddlers rather than a health agency, says that in water below 60°F an average person can hold their breath only one-third as long as in warmer water.
How long the dangerous part of a plunge lasts
You will see 30 seconds, one minute and the first few minutes all quoted. They come from different sources, and none is an all clear.
The exercise scientist quoted by American Heart Association News calls the first 10 seconds to a minute the most dangerous time. The National Weather Service says gasping and rapid breathing occur during the first 2 to 3 minutes or more.
In a study of healthy children in cold water, heart rate and breathing peaked at 30 seconds and began to normalize after 60 seconds.
The National Weather Service adds that loss of muscle control can be felt within seconds and gets worse the longer you stay and the colder the water. So treat the first minute with the most care, and keep the whole plunge short.
Cold shock is not the only risk in a cold plunge
Cleveland Clinic lists hypothermia first among the risks: prolonged exposure can lower core temperature, causing shivering, confusion and even unconsciousness. American Heart Association News says water takes heat away from the body 25 times faster than air.
It also lists frostbite or skin damage from overly long plunges, more likely as the water gets colder, and numbness and reduced motor control that make it hard to get out of the water safely.
In open water, the early minutes do the most damage. A 1989 review concluded that cold shock can kill long before general hypothermia develops, and a 2026 review says hypothermia develops only after sustained exposure. A 2017 review from the University of Portsmouth examines cold water as a precursor to drowning, cardiac arrest and hypothermia.
Those are open-water drownings, not tubs. PubMed searches on Nov. 3, 2026 found no count of injuries or deaths in plunge tubs, so we cannot tell you how low the risk is for a healthy adult.
Why a cold plunge can stress the heart
Shattock and Tipton proposed in 2012 what they call autonomic conflict. The cold shock response drives the heart faster and the diving response slows it, and submersion and the release of a held breath can set off both. They suggest both firing at once may explain arrhythmias, and in some vulnerable people deaths blamed on drowning or hypothermia.
They also report that cold water submersion can induce a high incidence of arrhythmias in healthy volunteers. That is submersion, which is the reason to keep your head above water.
Harvard Health says extra adrenaline can disrupt the heart’s rhythm, and that this usually isn’t a problem in someone with a healthy heart. In a study of healthy 15 and 16 year olds, brief body immersion in ice-cold water showed a low risk of severe arrhythmias, and the authors warn the risk could increase with face submersion and breath-holding.
The people most at risk are the least studied. The preventive cardiologist quoted by American Heart Association News notes that little research included people with heart conditions.
One small study of 37 men, 25 of them with heart failure or coronary artery disease, reported that a sauna then a cold immersion at 12°C was well tolerated. That was a measured study, not clearance to do it unsupervised.
Who should avoid cold plunging, and who should ask first
It is easy to reduce this to a line about checking with your doctor. The sources are firmer for some groups, so we sorted each group by the source’s own wording: told to avoid it, or told to ask first.
Do not read an empty cell as safe. An empty cell means none of the sources we read said it.
| Group | Told to avoid it, or told it is not advised | Told to ask a clinician first |
|---|---|---|
| Cardiovascular disease now or in the past, or any cardiac history | Harvard Health. The American Lung Association says most healthcare providers advise against it. The cardiologist in American Heart Association News would caution against it | Cleveland Clinic, NewYork-Presbyterian, Plunge |
| Heart rhythm disorder, such as atrial fibrillation | Harvard Health | |
| Long QT syndrome or another inherited rhythm disorder | No health page we read names it | Ask your cardiologist. A 2020 review reports a strong association between long QT and swimming, and the 2026 review names these conditions as a candidate cause of sudden death in cold water |
| Peripheral artery disease | Harvard Health | Plunge, for circulatory system problems |
| Raynaud’s | Harvard Health. The NHS says to try to avoid sudden changes in temperature | NewYork-Presbyterian |
| Cold urticaria | Cleveland Clinic: avoid cold baths and showers | |
| Sickle cell disease | The NHS: avoid getting into very cold water | |
| High or low blood pressure | Cleveland Clinic for high, Plunge for low or high. Neither limits this to uncontrolled pressure | |
| Past stroke or raised stroke risk | Cleveland Clinic says the strain can be dangerous with elevated stroke risk. The National Weather Service says the spike can cause stroke in vulnerable people | |
| Pregnancy, or possibly pregnant | Ice Barrel: not recommended | Cleveland Clinic, the American Lung Association, Plunge, Renu |
| Diabetes | Cleveland Clinic, Plunge | |
| Poor circulation, venous stasis or cold agglutinin disease | Cleveland Clinic | |
| Peripheral neuropathy, multiple sclerosis or another neurological disorder | Cleveland Clinic for neuropathy, NewYork-Presbyterian for all of these | |
| Chronic lung disease | The American Lung Association, which warns of hyperventilation leading to dizziness or fainting | |
| Epilepsy or a seizure disorder | No cold plunge page we read names it. Ask your neurologist. The NHS says to think about safety when swimming and to have showers instead of baths if you can | |
| Beta blockers, or medicine that causes drowsiness or affects heart rate, blood pressure or circulation | American Heart Association News on beta blockers, Plunge on the rest. Cleveland Clinic adds sedatives, opioids, phenothiazine antipsychotics and clonidine | |
| Obesity | Plunge | |
| Children and teens | Ice Barrel: not recommended. Renu: not designed for under 18. Plunge: no one under 18 unless a medical professional approves and they are supervised at all times | The American Academy of Pediatrics says hypothermia can occur more quickly in children than in adults |
| Older adults | MedlinePlus lists the very old and very young among those at higher risk of hypothermia | |
| Sick, vomiting, diarrhea, an infectious disease or open wounds | Renu. Plunge for infectious disease | |
| After alcohol or drugs | Plunge, Renu |
Six groups carry a plain avoid or not advised from a health source: past cardiovascular disease, rhythm disorders, peripheral artery disease, Raynaud’s, cold urticaria and sickle cell disease. If you are in one of those, a general all clear from a studio or a tub maker does not change it.
Our guides go further on atrial fibrillation, lupus, which is often linked to Raynaud’s, blood pressure, pregnancy, medications, diabetes, asthma, older adults and children and teens.
How long and how cold: the limits the sources print
Cleveland Clinic gives the plainest numbers. Avoid going below 40°F, and for beginners a safe starting range is 50 to 59°F. A session should never go longer than five minutes, and beginners should keep to a minute or two, once or twice a week.
Others differ at the top end. NewYork-Presbyterian says to start with something like 30 seconds and, in most cases, not to go beyond 15 minutes because of hypothermia.
Renu’s manual says 1 to 2 minutes for new users and a maximum of 5. We use the shorter limit.
Warmer water does not remove cold shock. The National Weather Service says it can be just as severe at 50 to 60°F as at 35°F, and that the gasp can be triggered by water as warm as 77°F.
In a 1991 lab study of eight people, the first responses at 10°C could be as great a threat as those at 5°C. So a warm tub does not change the answer if you are in one of the groups above.
Studios advertise colder water than these limits: of 16 we read, 8 list water below 40°F. Our temperature and time guide has the table, and where the other numbers come from.
The rules for getting in and out of a cold plunge
Each of these is printed by a health source or a maker. We found no study that tested them in plunge tubs, so treat them as precautions, not proven rules.
- Never alone. “Never, ever do a cold water swim on your own”, says the scientist American Heart Association News quotes. Renu says not to leave the tank unattended while in use, Ice Barrel recommends always having a partner present, and NewYork-Presbyterian says to have someone with you who can assist.
- No alcohol or drugs. Plunge says they can greatly increase the risk of fatal hypothermia, unconsciousness or drowning. CDC says alcohol is involved in up to 70% of deaths associated with water recreation among adolescents and adults.
- No jumping or diving. Plunge warns of serious or life threatening injury. Renu says to lower yourself gradually. We found no study that compared slow entry with jumping for the size of the gasp.
- Head above water, no breath-holds. The sources above tie arrhythmia risk to face submersion and breath-holding, and CDC has documented drownings from breath-holding underwater. In the 1991 study, a minute of hyperventilating first did not reduce the breathing response.
- Check the water. Cleveland Clinic says to use a thermometer. Plunge says temperature controls may be off by as much as 5°F.
- Know when to get out. Cleveland Clinic says lightheadedness or discomfort beyond just the sensation of being cold. Renu adds numbness and dizziness. Numb hands make climbing out harder, so do not wait for them.
- Get out slowly and stay with someone. Plunge says to use caution when entering and exiting, and Renu to exit slowly. Your companion should stay until you are dry, dressed and steady.
At a studio, tell staff when you go in. Some venues sell private rooms, as Lizard Yoga and 815 Refresh do, so ask who can see you. At home, our guide to home setups covers the electrical and water rules.
Planning a New Year’s Day dip in open water? Our guide to polar plunge safety covers cold shock in the first minutes, how long to stay in and how to warm up.
Does the cold shock response fade with practice?
Yes, in healthy volunteers. A 2024 systematic review found it habituates after about 4 immersions, with lower heart rate and breathing responses.
In one experiment, eight men did six 3-minute immersions at 15°C and still had a reduced response at 10°C seven months later. By 14 months their breathing response had gone back toward where it started.
Warmer water can do the training. Tipton’s 1998 study found habituation from water warmer than the temperature you want protection for, which is a reason to start in the warm tub. Showers are a weaker stand-in: in one study, repeated 10°C showers reduced the breathing response but 15°C showers did not.
This is not protection for anyone in the table above, and the 2024 review measured heart rate and breathing, not arrhythmias. The 2020 review still names cold shock as a risk of death in people unfamiliar with cold water.
What is afterdrop, and should you worry?
Afterdrop is a continued fall in core temperature after you leave the water. We found no study that timed it after a short plunge, so be wary of any exact number of minutes you read.
The two nearest studies, 3 minutes at 15°C and brief ice water dips in winter swimmers, reported no effect on core temperature. In longer swims it is well documented: in the Alcatraz swim study, 10 of 11 swimmers had it.
Dry off, dress warmly, and wait until you are steady before a hot shower, a sauna or driving. The sources disagree on the sauna: Cleveland Clinic says you may want to try one after a plunge, while NewYork-Presbyterian says a safer approach might be to let your body return to normal temperature first.
Our guide on what to do after a cold plunge has the studies and the signs that mean call 911. If you are cycling hot and cold on purpose, our contrast therapy guide covers the limits.
Cold plunge safety at a glance
| Question | What the sources say | Who says so |
|---|---|---|
| Is it safe for a healthy adult? | Risks are named, but we found no count of how often harm happens | Cleveland Clinic; our PubMed searches |
| Heart disease or a rhythm disorder? | Not advisable, or avoid | Harvard Health |
| High blood pressure, diabetes, pregnancy? | Talk to your provider first | Cleveland Clinic |
| How long? | A minute or two as a beginner, never longer than five minutes | Cleveland Clinic |
| How cold? | 50 to 59°F for beginners, not below 40°F | Cleveland Clinic |
| Is warmer water free of cold shock? | No: it can be as severe at 50 to 60°F as at 35°F | National Weather Service |
| Alone? | Never | American Heart Association News, Renu, Ice Barrel |
| Alcohol? | Never before or during | Plunge, Renu |
| When to get out? | Lightheaded, numb, dizzy, or discomfort beyond the cold | Cleveland Clinic, Renu |
| When to call 911? | Confusion, slurred speech, chest pain, shivering you cannot control, a faint you do not recover from, going under | MedlinePlus, 2024 first aid guidelines, CDC |
FAQ: cold plunge safety
Can a cold plunge cause a heart attack?
It can in someone vulnerable. NewYork-Presbyterian’s sports medicine article says the strain on the heart can result in cardiac events like heart attacks. We found no count of how often that happens in plunge tubs, and anyone with a cardiac history should talk to a cardiologist first.
Is a cold plunge safe if I am healthy?
We cannot give you a number, because we found no count of injuries in plunge tubs. Harvard Health says rhythm disruption usually isn’t a problem in a healthy heart, but Cleveland Clinic still lists hypothermia, skin and nerve damage, breathing problems and numbness as risks. Keep to the limits and never go alone.
Is 50°F safer than 40°F?
For how fast you cool, yes: a pooled analysis found more core cooling with colder water, and Cleveland Clinic sets 40°F as its floor. For cold shock, not necessarily: the National Weather Service says it can be as severe at 50 to 60°F as at 35°F.
How long can you safely stay in a cold plunge?
Cleveland Clinic says beginners should keep to a minute or two and that a session should never go longer than five minutes. Other sources print longer limits. We found no trial that tested safety limits in the general public.
Can I cold plunge with high blood pressure?
Talk to your provider first. Cleveland Clinic lists high blood pressure without limiting it to uncontrolled pressure, and says constricted blood vessels raise blood pressure and force the heart to work harder. Our blood pressure guide goes further.
Can you cold plunge while pregnant?
Ask your provider first. PubMed searches on Nov. 3, 2026 found no trial of cold water immersion in pregnancy. Cleveland Clinic, the American Lung Association, Plunge and Renu all say to ask, and Ice Barrel says it is not recommended. Our pregnancy guide covers it.
Can I cold plunge alone at home?
The sources say no. Renu says not to leave its tank unattended while in use, and Ice Barrel recommends a partner. The American Lung Association says that if cold shock leads to fainting while unsupervised, the person is at risk of drowning.
Does a cold plunge get safer with practice?
The cold shock response does shrink, after about 4 immersions in the 2024 review of healthy volunteers. That does not make a plunge safe for anyone with a heart condition.
The bottom line on cold plunge safety
Cold water is not safe for everyone, and the size of the risk for a healthy adult in a tub is unknown: we found no count. If you have had cardiovascular disease or have a rhythm disorder, peripheral artery disease, Raynaud’s, cold urticaria or sickle cell disease, the sources say to avoid it. Take any exception to your own clinician.
If you do plunge, keep to a minute or two at 50 to 59°F, never longer than five minutes, with someone beside you and no alcohol. Know the 911 signs at the top of this page before you get in.
For what cold water does and does not do when you are in the clear, see our ice bath and cold plunge guide.
Related reading on cold plunge safety
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