Some medicines and conditions change how your heart, circulation and temperature control respond to cold. This page gives general information only and cannot tell you whether cold water immersion is safe for you. The RNLI advises speaking to a health care professional before your first open water swim or cold water dip, and your GP or pharmacist is the right person to ask.
Why cold water can matter for health
The Irish Coast Guard, Water Safety Ireland and the RNLI warn that cold water shock can occur in water below 15°C. The RNLI says water under 15°C can seriously affect breathing and movement. The American Lung Association adds that cold water narrows blood vessels, which raises blood pressure and makes the heart work harder, and that cold shock can cause rapid, uncontrolled breathing, dizziness or fainting.
In a healthy person the response is usually short-lived. In someone with a heart or circulation condition, or on a medicine that changes heart rate or blood pressure, the same response may carry more risk. Fitness does not remove it, and undiagnosed conditions are a particular worry, which is another reason to get a check before you start.
Conditions to raise with a GP
The American Lung Association lists people with high blood pressure, heart conditions, or chronic heart or lung disease, along with pregnant people, children and older adults, as groups who should be cautious or avoid cold plunges and saunas. For heart conditions, it says most healthcare providers advise against cold plunges. Our wider page on who should not do cold water immersion covers these groups.
| Condition or situation | Why it is worth asking first | Source basis |
|---|---|---|
| Heart disease, irregular heartbeat | Cold narrows blood vessels and makes the heart work harder | American Lung Association; RNLI advises seeing a health professional |
| High blood pressure | Cold raises blood pressure. Uncontrolled hypertension is a reason not to start until your GP has reviewed it. If it is well controlled, ask your GP whether cold exposure is reasonable for you and what limits to set | American Lung Association; University of Portsmouth screening list |
| Anticoagulants (for example warfarin) | These raise the risk of bleeding, so a fall, knock or head injury on slippery rocks or steps matters more. Ask your clinic what precautions apply | NHS warfarin page |
| Previous stroke or TIA | Sudden rises in blood pressure and heart rate are a concern after a stroke or mini-stroke, so ask your GP or stroke team before any cold exposure | General caution; ask your GP |
| Raynaud's phenomenon | Cold is the usual trigger for fingers and toes turning white, blue then red | HSE |
| Chronic lung disease | Cold shock affects breathing, and dry or hot air can also cause problems | American Lung Association |
| Pregnancy | Listed among groups advised to be cautious | American Lung Association |
| Diabetes | Unstable diabetes is on the University of Portsmouth screening list. If you take insulin or a sulfonylurea, low blood sugar (hypoglycaemia) is a risk with exercise, and its warning signs such as confusion or shakiness can be confused with cold effects. Ask your diabetes team how to plan | University of Portsmouth; ask your diabetes team |
| Feeling unwell, recent illness or infection | Not a good time to add stress to the body | General caution; ask a GP |
Medicines: what to ask
There is no single list of medicines that are safe or unsafe for cold water, and no individual advice can be given here. The HSE's page on beta blockers gives one example of why the question matters. It says beta blockers work by slowing the heart and blocking hormones like adrenaline. It also says that cold hands or feet are a common side effect, and that dizziness and breathing difficulties can be signs of a very slow heart rate. It advises that you should not stop taking beta blockers without asking your GP, because stopping suddenly can worsen your condition.
That example is not a statement that anyone on beta blockers must avoid cold water. It shows that a medicine can change how your body responds, and that the decision belongs with someone who knows your health history. The same logic applies to other medicines that act on the heart, blood pressure, blood sugar, breathing or alertness.
Do not stop, skip or alter a prescribed medicine so that you can swim. Ask your GP or pharmacist whether swimming is advisable with your treatment, and follow their answer.
Questions to take to your GP or pharmacist
- I take [name of medicine]. Could it affect my heart rate, blood pressure or circulation when I get into water below 15°C?
- Could it make me dizzy, drowsy or faint, or affect my reaction to sudden cold?
- Does my condition make cold water shock more risky for me?
- Would you advise a cold shower, a short tub dip or open water, or none of these?
- Are there warning signs during or after a swim that mean I should stop and seek help?
- Should I have any tests first, for example a heart check, before I start?
Bring a list of everything you take, including over-the-counter medicines and supplements. The HSE advises telling your GP or pharmacist about any other medicines, supplements or conditions you have.
If you get the all-clear
A positive answer from a GP does not remove the need for safe habits. Enter slowly, keep your first swims short, go with a buddy and tell someone onshore your plans, as the RNLI and the joint seasonal appeal advise. See the cold water safety checklist and cold water shock and Float to Live.
Stop and seek help if you have chest pain, palpitations, severe breathlessness, confusion or numbness that does not recover. In an emergency, call 999 or 112. If someone is in trouble in the water, ask for the Coast Guard. For the research side of the question, see cold water immersion health benefits evidence.
Finally, be wary of any website or social media post that offers a personal verdict on your condition. Only a clinician who knows your history can say whether cold water immersion is right for you.
Frequently asked questions
Can I swim in cold water if I take medication?
That depends on the medicine and your health, so ask your GP or pharmacist. This page cannot give individual advice.
Should I stop my tablets before a swim?
No. Never stop, skip or change a prescribed medicine to suit a swim, and speak to your GP if you have concerns.
Why do beta blockers come up so often?
The HSE says they slow the heart and that cold hands or feet are a common side effect, so it is a useful example of why to ask first.
Who does the RNLI say to ask?
A health care professional, before your first open water swim or cold water dip.