02/08/2018 07:00 BST | Updated 03/08/2018 10:21 BST

What The Heatwave Is Doing To Your Body: From Your Heart To Your Kidneys

It's not just sweat.

The end of this week is set to be a real scorcher around the UK, with highs of 31°C expected in some places in the south of England. While a bit of sunshine often brings out the best in us, the soaring temperatures aren’t so great for health – particularly among the elderly, younger children and pregnant women.

In light of heatwave part two hitting Europe, we looked into exactly how these high temperatures impact the body. Spoiler alert: your organs aren’t so keen.

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When it’s hot for an extended period of time, the body’s internal temperature may rise, making the heart rate increase and vessels expand to bring more blood to the outer layers of skin, where the heat is then released. If this heat isn’t released fast enough or the surrounding air is warmer than the body, your sweat glands will try to cool you down. 

This is all well and good, but Dr Luke Powles, associate clinical director for Bupa Health Clinics, says sweating means a loss of fluid. “This can lead to a drop in blood pressure,” he explains, “causing the heart to beat more rapidly, making the heart work harder to maintain a cooler body.”

“People with heart conditions and other underlying medical problems – and those on certain medications – can be particularly sensitive to increasing temperatures and therefore at a higher risk of becoming unwell in a heatwave,” he says. This is why it’s imperative to stay hydrated during the hotter weather.


Part of the brain called the hypothalamus controls our core body temperature and is also responsible for sending signals to the skin to start sweating. However when it becomes too hot, these signals may not get through properly.

Dr Powles explains: “We shouldn’t see this from the forecast temperatures –  however, in extreme cases where your body temperature goes over 40°C, this can stop nerve fibres from working properly, which means the messages may not get through to and from the brain.”

While some parts of the UK are set for temperatures in the early thirties; in Spain, Portugal and some areas of France the mercury is expected to soar past 40°C later this week - with highs of 48°C expected in some places.

When the body temperature goes higher than normal it can lead to dizziness, feeling weak and tired, poor co-ordination, and even problems with balance or thinking, says Dr Powles. “Your skin can also turn pale, cold and dry with loss of sweating, if it stops receiving messages from the brain.”

Dr Kenny Livingstone, a registered GP and chief medical officer of ZoomDoc, says at a cellular level membranes, mitochondria and DNA can become damaged in extreme heat which raises the risk of stroke and swelling in the brain. “If high internal core body temperatures are sustained – it can ultimately prove fatal,” he adds.


Another symptom of heat-related illness is breathing more quickly. Dr Powles says the hot weather can put more strain on the lungs, especially if you already suffer from conditions such as COPD or asthma. 

The summer months also mean there are higher levels of pollen and, in some cities, air pollution which can also impact your breathing. “If you feel the heat is negatively impacting your breathing, try staying indoors more often, in well-ventilated areas,” Dr Powles advises.


The hot weather can also be “dangerous” for the liver, which is another thermosensitive organ. “Serious conditions such as heatstroke can damage liver cells, reflected by increased levels of liver enzymes in the blood,” Dr Powles explains.

Heatstroke is when the core body temperature rises above 40°C and the body’s internal systems begin shutting down. This can impact the nervous system and, if left untreated, can harm specific organs too.

“At its worst, this can lead to overall liver damage, although liver injury is often self-limiting,” says Dr Powles. “If you are suffering from any symptoms of heatstroke, it’s vital to get treatment immediately.” (Find out about signs of heatstroke here.)


Studies have linked heatwaves to an increased likelihood of kidney disease for those increasingly exposed to heat.

“As well as dehydration and a drop in blood pressure, both of which can harm the kidneys, in hot weather the body’s energy requirements can exceed its ability to produce energy, causing muscle cells to break down and release a protein called myoglobin and other products into the bloodstream,” Dr Powles explains. “Some of these breakdown products (including myoglobin) can be toxic to the kidneys and can directly damage them.”

He adds that while illnesses such as heatstroke can eventually be a cause of kidney failure, it’s important to know that this would result from a combination of events and, if treated, can be managed properly before it reaches this stage.

“Rehydrating the body will be essential in treating and protecting the kidneys from heatstroke.” 

Health advice for the hotter weather

:: Drink plenty of fluids.

:: Don’t stay out in the sun for too long, especially during the hottest times of the day (11am-3pm).

:: Stay in cool, well-ventilated areas where possible.

:: Don’t over exert yourself in hot weather – exercising at cooler times of the day is preferable.