Who should skip the sauna: alcohol, medications, pregnancy, and heart conditions

Most of what is written about sauna is about the benefits. This post is about the exceptions, because a heart rate tracker is not much use if the reason your heart rate is doing something strange is a beer or a beta blocker.

This is general information, not medical advice. If anything below applies to you, the right next step is a conversation with your doctor, not a sauna.

Skip the sauna if you have been drinking, have a hangover, a fever, or feel unwell. Ask a clinician first if you take beta blockers, diuretics, or blood pressure medication, if you have any unstable heart condition (recent heart attack, unstable angina, severe aortic stenosis, uncontrolled arrhythmia or blood pressure), or if you are pregnant and new to sauna. Reviews of the Finnish evidence find sauna well tolerated by healthy adults, children, and people with stable, treated heart disease, but that is a population finding, not clearance for you.

Avoid the sauna after drinking

Finland has about two million saunas for a little over five million people and has studied sauna deaths carefully. A forensic review of every sauna death in the country from 1990 to 2002 found that about half of the people who died were under the influence of alcohol, and concluded that prevention should focus on drinking less and never leaving a drunk bather alone. Not extreme heat, not long sessions: drinking is the leading avoidable factor. Japanese data point the same way: in a study of bath-related deaths in Tokyo, about a quarter of autopsied cases had blood alcohol above 0.5 mg/mL.

Alcohol affects judgment, balance, blood-pressure regulation, and hydration. Combined with heat and sweating, reviews of sauna safety say it raises the risk of low blood pressure, arrhythmia, and sudden death, and in practice fainting, falling, and overheating.

The rule is short: no sauna after drinking, and no drinking in the sauna. A beer afterwards, once you have cooled down and rehydrated with water, is a different matter and a Finnish tradition.

Medications that change the picture

Several common medications interact with heat. None of these is an absolute ban, but each is a reason to ask your doctor and to be conservative.

• Beta blockers (for blood pressure, heart rhythm, or anxiety) hold your heart rate down. Your heart rate will not climb the way this blog describes: in a sauna trial in coronary patients, many of them on beta blockers, heart rate at the end of a session was only about 96 bpm. Heart rate alerts and the "double your resting rate" rule of thumb stop being reliable guides. Go by time and by how you feel, keep rounds short, and know that your body's cooling response is also reduced.
• Diuretics ("water pills") start you off with less fluid. Sweating out another half litre can tip you into dizziness. Drink before, keep rounds short.
• Blood pressure medications in general, and vasodilators in particular, add their effect to the heat's. A review of sauna health effects notes that antihypertensive medication can predispose to a drop in blood pressure on standing after bathing. Standing up too fast after a round is the risk. Stand slowly, sit down again if you feel faint.
• Anticholinergic medicines can reduce sweating and may interfere with temperature regulation.
• Stimulants (ADHD medication, decongestants, a lot of caffeine) raise heart rate and body temperature on their own. Stack heat on top with care.
• Sedatives and sleep medication slow your reaction to feeling unwell. Do not combine. Japan's Consumer Affairs Agency lists bathing after taking tranquillisers or sleeping pills among its bath-safety warnings for the same reason.

Do not stop a medicine or change its timing on your own. Ask the prescribing clinician or a pharmacist whether sauna use is appropriate and follow their advice.

Heart conditions

Some studies include people with stable cardiovascular disease: a 2021 study of 22 patients with stable coronary artery disease found two 10 minute rounds at 81°C raised heart rate by about 27 bpm and lowered blood pressure without incident, and a 2016 study found that sauna followed by cold immersion did not provoke dangerous rhythms in stable heart failure patients. But a diagnosis alone cannot establish that sauna is safe for an individual. Symptoms, treatment, and exercise restrictions vary. Do not use the ability to walk briskly as medical clearance; ask your clinician.

The exceptions are the unstable situations, which the Mayo Clinic Proceedings review of sauna evidence lists as contraindications:

• Recent heart attack or unstable angina: wait until your cardiologist clears exercise, then treat sauna like exercise.
• Uncontrolled high blood pressure: get it controlled first. The sauna lowers blood pressure during recovery, but the transitions are the risk.
• Severe aortic stenosis and some other valve conditions: the drop in blood pressure from vasodilation can be dangerous. Ask.
• Arrhythmias that are not well controlled: heat and dehydration are both triggers.
• Recent stroke: same as heart attack. Wait for clearance.

And a specific caution for the cold plunge: cold water immersion causes a sharp rise in blood pressure and heart rate in the first seconds, the cold shock response. That is the single most demanding cardiovascular moment in the whole sauna cycle, and reviews of cold water immersion list cardiac events among its real hazards. For anyone with a heart condition, the cold plunge is the part to leave out first.

Pregnancy

Finnish women sauna throughout pregnancy, at moderate temperatures and short durations, and a Finnish study of late pregnancy found no adverse effect on uterine contractions or fetal heart rate at moderate exposure. A 2019 systematic review pooled the evidence and concluded that up to 20 minutes in a 70°C dry sauna, or a 40°C bath, did not push core temperature past the 39°C threshold that matters for the fetus. Guidance elsewhere is more cautious, particularly in the first trimester, when raising core body temperature significantly is a known concern.

Advice during pregnancy varies with the pregnancy and local clinical guidance. Ask your maternity-care professional before using a sauna rather than choosing a temperature or duration on your own.

Children

Children in Finland go to the sauna from infancy, with a parent, on the lowest bench, for a few minutes; the Finnish Sauna Society reports a first visit at a mean age of 4.5 months and babies kept in the hot room under five minutes. Their bodies regulate temperature less efficiently than adults, so the same room is hotter for them, and a study of 61 children at 70°C found that the heart's stroke volume fell by about a third in the under-fives and two children fainted. Short, low, supervised, and out the moment they want out. No cold plunge for small children.

Who should skip the sauna today?

• Fever or any acute illness. Your body is already running hot.
• Hangover. See alcohol above: you are dehydrated and your blood pressure regulation is off.
• Right after a heavy meal. Blood is going to your gut, not your skin.
• Right after intense exercise, without drinking first. Wait until you have rehydrated.
• Feeling faint, dizzy, or unwell for any reason.

Signs to leave now

Dizziness, nausea, headache, confusion, a racing or irregular heartbeat, or feeling suddenly cold in a hot room, which is a sign of heat exhaustion. Leave, sit down in a cool place, drink water, and do not go into cold water until you feel normal. If it does not pass in fifteen minutes, get help.

Read next: Saunaolut: the Finnish sauna beer · Sauna heart rate: what's normal?

Sources

• Kenttämies A, Karkola K. "Death in sauna." J Forensic Sci. 2008;53(3):724-729. https://doi.org/10.1111/j.1556-4029.2008.00703.x
• Suzuki H, et al. "Characteristics of sudden bath-related death investigated by medical examiners in Tokyo, Japan." J Epidemiol. 2015;25(2):126-132. https://doi.org/10.2188/jea.JE20140068
• Hannuksela ML, Ellahham S. "Benefits and risks of sauna bathing." Am J Med. 2001;110(2):118-126. https://doi.org/10.1016/S0002-9343(00)00671-9
• Debray A, et al. "Finnish sauna bathing and vascular health of adults with coronary artery disease: a randomized controlled trial." J Appl Physiol. 2023;135(4):795-804. https://doi.org/10.1152/japplphysiol.00322.2023
• Kukkonen-Harjula K, Kauppinen K. "Health effects and risks of sauna bathing." Int J Circumpolar Health. 2006;65(3):195-205. https://doi.org/10.3402/ijch.v65i3.18102
• Consumer Affairs Agency of Japan. "冬季に多発する入浴中の事故に御注意ください！" News release, 21 Nov 2018. https://www.caa.go.jp/policies/policy/consumer_safety/caution/caution_009/
• Gravel H, et al. "Acute vascular benefits of Finnish sauna bathing in patients with stable coronary artery disease." Can J Cardiol. 2021;37(3):493-499. https://doi.org/10.1016/j.cjca.2020.06.017
• Radtke T, et al. "Acute effects of Finnish sauna and cold-water immersion on haemodynamic variables and autonomic nervous system activity in patients with heart failure." Eur J Prev Cardiol. 2016;23(6):593-601. https://doi.org/10.1177/2047487315594506
• Laukkanen JA, Laukkanen T, Kunutsor SK. "Cardiovascular and other health benefits of sauna bathing: a review of the evidence." Mayo Clin Proc. 2018;93(8):1111-1121. https://doi.org/10.1016/j.mayocp.2018.04.008
• Tipton MJ. "The initial responses to cold-water immersion in man." Clin Sci (Lond). 1989;77(6):581-588. https://doi.org/10.1042/cs0770581
• Tipton MJ, Collier N, Massey H, Corbett J, Harper M. "Cold water immersion: kill or cure?" Exp Physiol. 2017;102(11):1335-1355. https://doi.org/10.1113/EP086283
• Vähä-Eskeli K, Erkkola R. "The effect of short-term heat stress on uterine contractility, fetal heart rate and fetal movements at late pregnancy." Eur J Obstet Gynecol Reprod Biol. 1991;38(1):9-14. https://doi.org/10.1016/0028-2243(91)90200-5
• Ravanelli N, et al. "Heat stress and fetal risk. Environmental limits for exercise and passive heat stress during pregnancy: a systematic review with best evidence synthesis." Br J Sports Med. 2019;53(13):799-805. https://doi.org/10.1136/bjsports-2017-097914
• Finnish Sauna Society. "A child in the sauna." https://sauna.fi/en/sauna-knowledge/a-child-in-the-sauna/
• Jokinen E, et al. "Children in sauna: cardiovascular adjustment." Pediatrics. 1990;86(2):282-288. https://doi.org/10.1542/peds.86.2.282

Quick answer

• Skip it: after alcohol, with a hangover, fever, or acute illness.
• Ask first: beta blockers, diuretics, blood pressure medication, anticholinergics, any unstable heart condition, pregnancy if you are new to sauna.
• Do not self-clear: even stable, treated heart disease requires individual advice from a clinician.
• Skip today: fever, hangover, heavy meal, dehydration, feeling unwell.