When temperatures climb, staying hydrated and keeping cool are usually the first things that come to mind. But for people taking certain medications, particularly older adults, extreme heat can pose an additional challenge..

Some medicines used to treat high blood pressure and heart conditions can affect the body's ability to regulate temperature or maintain its fluid balance. During a heatwave, this may increase the risk of dehydration, dizziness, and, in some cases, falls.

UK doctors have reported seeing older patients become dizzy and light-headed during periods of extreme heat, with some subsequently falling and suffering injuries. The concern is particularly relevant for people taking diuretics and blood pressure medicines.

How Can Blood Pressure Medication Affect You in the Heat?

The body naturally responds to heat by sending more blood towards the skin and producing sweat to help lower its temperature. Some medicines can interfere with these processes.

Diuretics, sometimes called 'water tablets', increase the amount of water and salt removed from the body through urine. When combined with heavy sweating, this can increase the risk of dehydration and electrolyte disturbances.

Some blood pressure medicines can also affect the body's ability to respond to heat. The UK's Medicines and Healthcare products Regulatory Agency (MHRA) says ACE inhibitors, beta-blockers, and calcium channel blockers can make it harder for the body to regulate temperature during sudden hot spells.

Beta-blockers, for example, can reduce blood flow to the skin, while some other medicines can affect sweating. These effects do not mean the medications are unsafe or should be stopped, but they can make it more important to take precautions during very hot weather.

Why Does Dehydration Cause Dizziness?

Sweating causes the body to lose fluid. If that loss is not adequately replaced, blood volume can fall, potentially contributing to low blood pressure.

This can become particularly noticeable when standing up. A sudden drop in blood pressure after changing position, known as orthostatic hypotension, can cause light-headedness, blurred vision, or dizziness and can increase the risk of falling. Some blood pressure medicines can make this effect worse in certain people.

Older adults may be particularly vulnerable because the body's ability to regulate temperature and respond to changes in blood pressure can become less efficient with age.

What Should You Do During a Heatwave?

If you take blood pressure medication, do not stop or change your dose yourself. Blood pressure treatment is prescribed to reduce the risk of serious complications such as stroke and heart disease, and suddenly stopping medication can, in some cases, cause blood pressure to rise.

Instead, the MHRA recommends taking extra care to stay hydrated and cool during hot weather, particularly if you take diuretics or blood pressure medication.

Try to stay somewhere cool during the hottest parts of the day, drink fluids regularly, and get up slowly after sitting or lying down if you are prone to dizziness.

It is also important to store medicines correctly. Most medicines should be kept below 25°C unless their packaging or patient information leaflet states otherwise. Heat can damage some medicines, particularly if they are left in hot cars, direct sunlight, or other excessively warm places.

When Should You Seek Medical Help?

Dizziness, weakness, headaches, nausea, excessive sweating, and a rapid heartbeat can be signs of heat exhaustion. Moving to a cool place and drinking fluids can help, but persistent symptoms warrant medical advice.

Confusion, loss of consciousness, poor coordination, slurred speech, or hot skin without sweating can indicate heatstroke, which is a medical emergency.

Ultimately, blood pressure medication should not be viewed as something to fear during a heatwave. The key is understanding how your individual medicines may interact with hot weather and speaking with a doctor or pharmacist if you develop new or worsening symptoms.

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