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 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, the latter of which is important for proper heart function - as well as salt are lost in greater amounts through 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 sharp temperature fluctuations 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. The sudden heat also leads to more frequent heart rhythm disturbances.

Medications and heat - what should you watch out for?

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

People who take diuretics to treat high blood pressure should monitor themselves particularly closely, for example. Because these medications promote fluid loss, the additional sweating in the summer heat can cause the body to lose too much fluid. It is advisable to discuss a possible dose reduction with the treating doctor.

ACE inhibitors and sartans may reduce the feeling of thirst under certain circumstances. This has not been fully established, but we would still like to point it out, as it is particularly important to drink enough in warm weather.

The Robert Koch Institute (RKI) published a report in September 2023 that, in addition to diuretics, highlights other blood pressure-lowering medications because heat can cause problems with them. These include beta blockers, ACE inhibitors, sartans, calcium channel blockers, clonidine and moxonidine. Here too, it is advisable to discuss with your treating doctor whether changing how you take these medications is advisable. The report lists the following side effect triggered by heat:

On the one hand, prevention of blood vessel dilation (beta-blockers) in the skin → reduced heat loss through convection, increased sweating threshold (central antihypertensives); on the other hand, enhancement of the blood pressure-lowering effect through vasodilation → drops in blood pressure

However, even people who do not need medication for their blood pressure may notice changes in their readings during summer temperatures. This is because even normal or high-normal blood pressure readings can fall due to the widening of the blood vessels and the reduced volume of fluid in the body (caused by sweating). Dizziness, circulatory problems, light-headedness, headaches and nausea are possible consequences. Sometimes this can even lead to circulatory collapse.

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

Ice-cold drinks actually cool you less effectively than lukewarm drinks, because the body responds to sudden intense cooling by raising blood pressure, and afterwards you tend to sweat more rather than less. The same applies to showering-better lukewarm than ice-cold.

On hot days, people with high blood pressure can have a little more salt than usual, because the body loses salt through sweating.

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.

You should move your workout to the morning, when the air is still fresh and the heat is not yet too intense.

You can take a cue from countries accustomed to hot weather. People there take a siesta at midday, and daily life is centered around the morning and evening hours.

Interesting findings on how to tell whether the body is or is about to become stressed by heat 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 exerting themselves. Heart rate can therefore indicate when you're entering heat stress and might want to look for ways to cool down.

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

Author Sabine Croci is a qualified medical assistant with many years of experience in internal medicine and cardiology practices as well as outpatient care, and has headed the specialist editorial team at Tensana since 2015. Thanks to her extensive additional qualifications as an emergency medical technician, first responder, and in various areas of therapy and emergency care, she provides well-founded, practical, and reliably verified information.

Blood Pressure and Heat

Medications and heat - what should you watch out for?

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