Blood Pressure and Heat

Summer, sun, and sunshine lift most people's spirits. But not everyone is happy about high summer temperatures. When the thermometer rises above about 25 °C (77 °F), it often puts strain on people with high blood pressure or heart or lung disease.

The warm temperatures cause the blood vessels to widen and the blood pressure to fall. In some people this effect is pronounced enough that medication doses need to be adjusted. Of course, that should never be done on your own but always in consultation with your treating doctor.

In the heat you also sweat more, which can upset your fluid balance. Minerals especially magnesium and potassium, which is important for proper heart function as well as salt are lost with sweat. So it's not just the body's fluid volume that drops; the mineral balance can be thrown off too.

For people with high blood pressure, it is more important than ever to measure blood pressure every day during the warm summer months. That way you can document whether and how much your blood pressure falls in the heat. And when the weather cools down again, this information tells you when it's time to bring the medication dose back up to the usual level. This is especially useful during prolonged heat waves.

Short-term strong temperature swings of more than five degrees from one day to the next, on the other hand, increase the risk of a heart attack by about 60% in people with high blood pressure. Sudden heat also causes more heart rhythm disturbances.

Medications and heat what should you watch for?

As mentioned at the beginning, the intake of certain medications may need to be adjusted for warm temperatures. This must always be done in agreement with your treating doctor.

People who take diuretics to treat high blood pressure should watch themselves particularly closely, for example. Because these drugs promote fluid loss, the extra sweating in summer heat can remove too much fluid from the body. It's a good idea to discuss a possible dose reduction with your doctor.

ACE inhibitors and sartans can possibly reduce the feeling of thirst. This is not completely clarified, but we point it out because it's important to drink enough, especially in warm weather.

The Robert Koch Institute (RKI) published a report in September 2023 that, in addition to diuretics, highlights other blood-pressurelowering drugs because heat can cause problems with them. Named are betablockers, ACE inhibitors, sartans, calcium channel blockers, clonidine and moxonidine. Here too, it's advisable to discuss with your treating doctor whether a change in how you take your medication is recommended. As a side effect triggered by heat, the report lists:

On the one hand, prevention of dilation of blood vessels (betablockers) in the skin reduced heat loss through convection, increased threshold for sweat secretion (central antihypertensives); on the other hand, enhancement of the blood-pressurelowering effect through vasodilation drops in blood pressure

But even people who don't need medication for their blood pressure can feel changes in their readings in hot weather. Normal or highnormal blood pressure values can fall because of the widening of vessels and the reduced fluid volume (from sweating). Dizziness, circulatory problems, lightheadedness, headaches and nausea are possible consequences sometimes it can even lead to fainting (circulatory collapse).

The best way to counteract this is to drink enough fluids. Mineral water or lightly diluted juice spritzers are good for keeping electrolyte balance in check. If you can only drink a limited amount per day because of a medical condition, you should discuss this with your doctor.

Icecold drinks actually cool you less effectively than lukewarm drinks, because the body responds to sudden strong cooling by raising blood pressure and you tend to sweat more afterwards. The same applies to showering better lukewarm than icecold.

On hot days, people with high blood pressure can allow themselves a bit more salt than usual, because you lose salt through sweat.

Take it easy on hot days. Wear loose, breathable clothing that lets your skin breathe. If possible, stay in cool rooms, but be careful with air conditioning. If rooms are cooled down too much, the shock when you step outside can be greater.

Your workout should be moved to the morning, when the air is still fresh and the heat is not yet strong.

You can take a cue from heataccustomed countries: they rest at midday and life takes place in the morning and evening hours.

Interesting findings on how to tell whether the body is or is about to be heatstressed came from a study published in 2023. It was observed that participants' heart rates rose about 20 minutes before the body was no longer able to keep its core temperature stable, even though they were not physically exerted. Heart rate can therefore be an indicator that you're entering heat stress and might want to look for ways to cool down.

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This article comes from BloodPressureDB – the leading app since 2011 that helps hundreds of thousands of people monitor their blood pressure every day. Our content is based on carefully researched, evidence-based information and is continuously updated (as of 01/2026).

Author Sabine Croci is a certified medical assistant with many years of experience in internal medicine and cardiology practices as well as in outpatient care. Since 2015 she has led the editorial team at BloodPressureDB. With additional qualifications as a paramedic, first responder, and training in various therapy and emergency areas, she provides well-founded, practical, and reliably reviewed information.

Blood Pressure and Heat

Medications and heat what should you watch for?

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