Cold plunging is not right for everyone. People with heart conditions, high or low blood pressure, Raynaud's, cold urticaria (hives triggered by cold) or epilepsy, and anyone who is pregnant, should speak to their GP or specialist before trying it. This article explains why, using guidance from the NHS, the British Heart Foundation, the RNLI and published research, but it is not medical advice: only your doctor can tell you what is safe for you.
Why cold water is a real stress on the body
The reason some people need to be careful comes down to what cold water does in the first minute. The RNLI explains that sudden immersion in water below 15°C causes an involuntary gasp, a rise in heart rate and a rise in blood pressure, and warns that this can lead to cardiac arrest. The British Heart Foundation adds that the colder the water, the harder the heart has to work. For a healthy person this is usually a short-lived, manageable response. For someone with certain conditions it can be a significant risk.
Heart conditions
This is the most important group. The British Heart Foundation says cold water can raise stress hormone levels, which may increase the risk of irregular heart rhythms and possibly cardiac arrest, while noting that more research is needed. It advises anyone with a heart condition to discuss the risks of cold water with their doctor or nurse specialist, and suggests that for people with heart conditions, a heated pool is likely to be a safer option than cold water.
A 2020 narrative review in the International Journal of Environmental Research and Public Health (Knechtle and colleagues) also notes that people with known or as yet unrecognised heart disease are more likely to experience rhythm disturbances in cold water. That second point matters: some heart problems are undiagnosed, which is one reason a GP check is sensible before you start if you have any symptoms or a family history that concerns you.
High or low blood pressure
Cold water shock raises blood pressure quickly, according to both the RNLI and the British Heart Foundation. If you have high blood pressure, or take medication for it, talk to your GP before trying cold plunging. If you have low blood pressure or are prone to feeling faint or dizzy, check with your GP as well, and take particular care getting in and out of the tub.
Pregnancy
There is very little research on cold water immersion in pregnancy. A 2025 scoping review and consensus statement in the journal Lifestyle Medicine (Shawe and colleagues), involving UK universities and NHS trusts, concluded that there is a lack of evidence-based guidance on the safety of cold water immersion during pregnancy. Its expert recommendations, which the authors describe as consensus opinion rather than findings from specific studies, include:
- Not starting cold water swimming during pregnancy if you have no previous experience.
- Avoiding it altogether if your blood pressure is raised or very low.
- Never swimming alone.
If you are pregnant, speak to your midwife or GP before any cold water immersion, including at home.
Raynaud's
The NHS explains that in Raynaud's, fingers and toes can change colour when you are cold, anxious or stressed. Its advice for managing the condition includes keeping warm and trying to avoid sudden changes in temperature. A cold plunge is, by design, a sudden change in temperature, so if you have Raynaud's, speak to your GP before trying it.
Cold urticaria (hives triggered by cold)
The NHS lists cold, including cold water, as a possible trigger for hives. In some people, reactions can be serious. The NHS says to call 999 if your lips, mouth, throat or tongue suddenly swell, your throat feels tight, or you are struggling to breathe, as these can be signs of a serious allergic reaction. If you have ever had hives or swelling after cold exposure, do not try cold plunging without speaking to your GP first.
Epilepsy
NHS guidance for living with epilepsy suggests having showers instead of baths where possible, and thinking about safety when swimming. A plunge tub is a body of water you sit in, so if you have epilepsy, discuss it with your GP or epilepsy specialist, and never plunge alone.
Situations where nobody should plunge
Even if you are generally healthy, skip your plunge if:
- You have had alcohol or taken drugs. Public Health Wales advises staying out of the water if you have had alcohol or taken drugs, and the Knechtle review notes that alcohol speeds the onset of hypothermia.
- You feel unwell. The British Heart Foundation advises only swimming when you feel well.
- You are alone. Public Health Wales advises avoiding swimming alone, and the same principle applies at home.
Other conditions and medications
This list is not complete. If you have any other medical condition, take regular medication, or are recovering from illness or surgery, check with your GP before you start. It is a short conversation, and it is the right one to have.
If your GP says yes
If you get the go-ahead, start gently. Begin warmer, around 13 to 15°C, keep sessions to a minute or two at first and build up slowly. A plunge with precise temperature control makes this easier. The ThermoX Pro, for example, can be set anywhere from 3 to 40°C, so you can start at a milder temperature and lower it gradually over time. See our cold plunge temperature guide and our article on cold water shock and plunging safely before your first session.
A short safety note
Speak to your GP first if you have a heart condition, high or low blood pressure, are pregnant or have any other medical condition. Cold water shock is real, as the RNLI makes clear. Never plunge alone or after alcohol, and always start warmer and shorter. You can find all of our basics articles in our cold plunge guide.
Frequently asked questions
Can I cold plunge with a heart condition?
Speak to your doctor or nurse specialist first. The British Heart Foundation says cold water may increase the risk of irregular heart rhythms and advises people with heart conditions to discuss the risks with their healthcare team.
Is cold plunging safe during pregnancy?
There is very little evidence either way. A 2025 consensus statement in Lifestyle Medicine advised against starting cold water swimming in pregnancy without previous experience, and against it altogether if blood pressure is raised or very low. Speak to your midwife or GP first.
Can I cold plunge if I have Raynaud's?
Check with your GP first. NHS advice for Raynaud's includes keeping warm and avoiding sudden changes in temperature, which is exactly what a cold plunge involves.
Should I see a GP before cold plunging if I feel healthy?
If you have no medical conditions and feel well, many people start without a GP visit. But some heart problems go undiagnosed, so if you have any symptoms, take medication or have a family history of heart problems, it is sensible to check first.