“Sauna lowers your blood pressure.”

The research found this

The most quoted numbers come from Kuopio, where 102 adults with at least one heart risk factor sat in a 73°C sauna for 30 minutes. Measured after they came out, systolic pressure had fallen from 137 to 130 mmHg and diastolic from 82 to 75, and systolic pressure was still below its starting level half an hour later.1Source 1 · Clinical trialAcute effects of sauna bathing on cardiovascular functionLaukkanen T, Kunutsor SK, Zaccardi F, et al.. Journal of Human Hypertension, 2018.Read the paper ↗PubMed ↗ The study had no control group, and the session included a two-minute shower halfway through.2Source 2 · Clinical trialShort-term effects of Finnish sauna bathing on blood-based markers of cardiovascular function in non-naive sauna usersKunutsor SK, Häkkinen A, Zaccardi F, et al.. Heart and Vessels, 2018.Read the paper ↗PubMed ↗

Readings taken inside the sauna vary with the heat and the method. Systolic pressure fell by 16 mmHg over 30 minutes at 73°C in one crossover study, while in 19 adults at 93°C systolic and diastolic pressure both climbed steadily and dropped below baseline only after they left.3Source 3 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗4Source 4 · Clinical trialThe blood pressure and heart rate during sauna bath correspond to cardiac responses during submaximal dynamic exerciseKetelhut S, Ketelhut R. Complementary Therapies in Medicine, 2019.Read the paper ↗PubMed ↗

In 16 adults with untreated high or borderline blood pressure, two short sauna bouts left pressure unchanged 15 and 120 minutes later and over the next 24 hours.5Source 5 · Crossover trialEffects of Sauna Alone and Postexercise Sauna Baths on Blood Pressure and Hemodynamic Variables in Patients With Untreated HypertensionGayda M, Paillard F, Sosner P, et al.. The Journal of Clinical Hypertension, 2012.Read the paper ↗PubMed ↗ The same study found lower 24-hour systolic pressure when the sauna followed 30 minutes of cycling. An eight-week Finnish trial pointed the same way: people who exercised and then sat in a sauna for 15 minutes ended with systolic pressure 8 mmHg lower than people who only exercised.6Source 6 · Randomized trialEffects of regular sauna bathing in conjunction with exercise on cardiovascular function: a multi-arm, randomized controlled trialLee E, Kolunsarka I, Kostensalo J, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2022.Read the paper ↗PubMed ↗

Longer trials of heat alone have mostly come up empty. Thirty sessions in 40°C water left 24-hour systolic pressure at 134 mmHg before and after in 41 adults with untreated hypertension, and blood pressure didn't budge after eight weeks of Finnish sauna in 41 adults with coronary artery disease.7Source 7 · Randomized trialNo effect of either heat therapy or aerobic exercise training on blood pressure in adults with untreated hypertension: a randomized clinical trialKaiser BW, Comrada LN, Gibson BM, et al.. Journal of Applied Physiology, 2025.Read the paper ↗PubMed ↗8Source 8 · Randomized trialFinnish sauna bathing and vascular health of adults with coronary artery disease: a randomized controlled trialDebray A, Gravel H, Garceau L, et al.. Journal of Applied Physiology, 2023.Read the paper ↗PubMed ↗ Pooling 20 randomized trials of passive heating gave a 2.46 mmHg fall in systolic pressure that fell short of significance, and the trials that heated the whole body showed a 4.11 mmHg drop.9Source 9 · Meta-analysisNon-acute effects of passive heating interventions on cardiometabolic risk and vascular health: systematic review and meta-analysis of randomized controlled trialsHamaya R, Joyama Y, Miyata T, et al.. American Journal of Preventive Cardiology, 2025.Read the paper ↗PubMed ↗

The Finnish cohort offers a long-term hint. Among 1,621 men who started without high blood pressure, those who took four to seven saunas a week had a 47% lower hazard of a hypertension diagnosis over a median of 24.7 years, though only 19 of them developed it.10Source 10 · Cohort studySauna Bathing and Incident Hypertension: A Prospective Cohort StudyZaccardi F, Laukkanen T, Willeit P, et al.. American Journal of Hypertension, 2017.Read the paper ↗PubMed ↗ In Japan, people who took a hot bath almost daily had 20% lower odds of developing hypertension within five years.11Source 11 · Cohort studyHabitual tub bathing and risks of incident coronary heart disease and strokeUkai T, Iso H, Yamagishi K, et al.. Heart, 2020.Read the paper ↗PubMed ↗