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Heat and Hypertension: What the New Blood Pressure Guidelines Mean During Hot Weather By Courtney Arianne Washington, DO Hot weather affects more than your comfort. It can change your blood pressure, hydration status, kidney function, and the way certain medications affect your body. In places like New Orleans, where I practice, high temperatures are often accompanied by intense humidity. In other parts of the world, people may face dry desert heat, prolonged heat waves, limited access to air conditioning, strenuous outdoor work, or unexpectedly high temperatures in regions that are not accustomed to extreme heat. The climate may look different, but the medical concern is the same: your body has to work harder to regulate its temperature, and that can become dangerous when you have high blood pressure or take certain cardiovascular medications. In emergency medicine, I have cared for patients who were taking their medications exactly as prescribed but still developed dizziness, weakness, dehydration, low blood pressure, electrolyte abnormalities, or kidney problems during periods of extreme heat. The medication may not have been wrong. The conditions surrounding the patient had changed. That is why blood pressure care should never be reduced to simply prescribing a pill and checking a number. The 2025 American Heart Association and American College of Cardiology High Blood Pressure Guideline emphasizes a more precise and individualized approach to hypertension. The blood pressure categories have not changed, but the way clinicians determine who needs medication—and how aggressively they should be treated—has become more personalized. This is especially important during hot weather, whether you are dealing with a Gulf Coast summer, a European heat wave, desert temperatures, a tropical climate, or a hot day spent working or exercising outdoors. Prefer to Watch Instead? Watch the full episode below, where I explain the updated hypertension guidance in plain language and discuss what it means during hot weather. × The First Major Blood Pressure Guideline Update Since 2017 The 2025 AHA/ACC guideline replaces the major hypertension guideline released in 2017. It continues the evolution away from the older JNC 8 approach, which many clinicians learned during training and may still remember. The current blood pressure categories are: Normal blood pressure: less than 120/80 mm Hg Elevated blood pressure: 120–129 systolic and less than 80 diastolic Stage 1 hypertension: 130–139 systolic or 80–89 diastolic Stage 2 hypertension: 140/90 mm Hg or higher For most adults receiving treatment, the recommended blood pressure goal remains less than 130/80 mm Hg. However, that target must still be considered within the context of the individual patient. A person who is frail, frequently becomes dizzy when standing, is at high risk of falling, has a limited life expectancy, or has other complex medical conditions may require a different treatment strategy. A treatment goal is not the same thing as an automatic treatment plan. Two People Can Have the Same Blood Pressure and Receive Different Treatment Consider two people who both have an average blood pressure of 135/85 mm Hg. One may be advised to begin medication. The other may be given several months to focus on nutrition, exercise, weight management, sodium reduction, sleep, and other lifestyle changes. Both approaches may be consistent with the guideline. The difference is their overall cardiovascular risk. Someone with diabetes, chronic kidney disease, a previous stroke, established cardiovascular disease, or a higher calculated risk of a future cardiovascular event may benefit from starting medication earlier. Someone without those risk factors may reasonably begin with intensive lifestyle changes and close follow-up before medication is added. This is not inconsistent treatment. It is individualized treatment. The PREVENT Calculator Changes the Conversation One of the most important updates is the use of the American Heart Association’s PREVENT™ cardiovascular risk calculator. PREVENT stands for Predicting Risk of Cardiovascular Disease EVENTs. It estimates a person’s 10-year and 30-year risk of developing cardiovascular disease, including heart attack, stroke, and heart failure. Unlike older cardiovascular risk models, PREVENT incorporates cardiovascular, kidney, and metabolic health. It was developed and validated using data from more than 6.5 million diverse adults in the United States and is intended for adults ages 30 through 79 who do not already have known cardiovascular disease. The calculator may include information such as: Age and sex Blood pressure Cholesterol levels Kidney function Diabetes status Smoking history Body mass index Use of blood pressure or cholesterol medication Additional information, including hemoglobin A1c, urine albumin-to-creatinine ratio, and measures related to social disadvantage, may further personalize the estimate. For a person with Stage 1 hypertension and no established cardiovascular disease, diabetes, or chronic kidney disease, a 10-year PREVENT cardiovascular risk of 7.5% or higher supports beginning medication along with lifestyle changes. When the calculated risk is below 7.5%, an initial three- to six-month trial of intensive lifestyle modification may be appropriate. If the average blood pressure remains at or above 130/80 mm Hg, medication is then recommended. The blood pressure reading matters, but it is no longer the only number guiding the decision. Although PREVENT was developed using United States data and is part of the current American guideline, the broader principle applies everywhere: blood pressure treatment should reflect the patient’s total cardiovascular risk, not one isolated reading. People outside the United States should discuss which cardiovascular risk tool and hypertension guideline are recommended in their country. What Happens When Blood Pressure Is 140/90 or Higher? An average blood pressure of 140/90 mm Hg or higher falls within Stage 2 hypertension under the AHA/ACC classification. For most adults in this range, lifestyle changes alone are not enough. Medication is generally recommended in addition to lifestyle treatment, regardless of the calculated PREVENT risk. The 2025 guideline also favors beginning treatment with two first-line medications from different drug classes for Stage 2 hypertension. Whenever possible, those medications may be combined into one pill. A single-pill combination can make the regimen easier to follow and may help patients reach their blood pressure goal faster than slowly adding one medication at a time. Blood pressure definitions and treatment thresholds can