Summer is great. But for your heart and blood vessels, tropical temperatures are a real challenge. Especially if you have a history of blood pressure issues yourself, or if you're looking after someone who does.
So what actually happens to blood pressure in the heat, and why is it worth keeping a closer eye on it during the summer months?
What heat does to your blood pressure
Your body tries to cool itself down in hot weather. Blood vessels near the surface of the skin dilate to let heat escape, and you sweat more. But wider blood vessels also mean lower resistance, which leads to lower blood pressure. Add to that the loss of fluids and minerals through sweating, and the volume of blood in circulation drops further still.
It's not the same story for everyone, though. In some people, heat actually pushes blood pressure up. The heart has to work harder to cool the body down, and in combination with humidity or dehydration, readings can climb to a level you'd rather avoid.
The result can be dizziness when you stand up, unusual tiredness, a racing heart or a persistent headache. Things you might easily put down to the heat in summer, and yet they're signals worth paying attention to.
Who needs to be particularly careful
Not everyone handles hot weather the same way. Those who need to be most careful include:
Older adults. As we age, the body becomes less effective at regulating temperature and picking up on thirst signals. An older person can be dehydrated without feeling thirsty at all.
People with high blood pressure. Heat and humidity can strengthen or weaken the effect of blood pressure medication, so readings may behave differently than you're used to.
People taking diuretics. Water tablets combined with summer sweating significantly increase the risk of dehydration, more than most people realise.
People with heart conditions. Hot weather puts direct strain on the heart. It raises heart rate and, in extreme cases, can trigger more serious events.
If any of these apply to you, it's worth talking to your doctor before the hottest part of summer arrives. Even just to check whether your medication dose needs any adjustment.
What helps: a few practical things
Drink before you feel thirsty. A glass of water every half hour is a good baseline. If you're active or it's particularly hot, double that.
Avoid direct sun between 11am and 4pm. That's when the strain on your body is highest.
Get up slowly. Changing position quickly in the heat makes dizziness more likely. Your body needs a moment to adjust blood flow.
Shower with lukewarm water, not cold. A cold shower causes blood vessels to constrict, which makes your body generate more heat and sweat even more. Lukewarm water is actually more effective.
Don't overdo physical activity. Morning or evening exercise is fine. An afternoon bike ride in 34°C is not a great idea for anyone with blood pressure concerns.
Why it's worth having a blood pressure monitor at home in summer
Regular monitoring gives you a picture you simply can't get any other way. You can see whether your readings are dropping, rising or fluctuating during hot days. And if you ever need to see a doctor, you'll have actual numbers to show them.
Truelife Pulse monitors are deliberately simple to use. The basic Truelife Pulse is straightforward for anyone. It has a large, easy-to-read display, one-button operation, memory for 60 readings and a high blood pressure indicator that alerts you automatically if readings go above normal. It runs on batteries or USB, so you can take it with you to a summer cottage or on holiday.
If you want more, the Truelife Pulse B-Vision adds colour-coded results based on WHO guidelines. You can see at a glance on the display whether your reading is normal, borderline or in the risk zone, with no need to look anything up or compare against a chart. The voice assistant reads results aloud, which is especially helpful for older users or anyone who finds smaller displays difficult to read. The device stores up to 120 readings for two separate users, so it can easily serve a whole household.
For those who want their data always to hand, there's also the Truelife Pulse BT, a Bluetooth monitor that pairs with a smartphone app and displays your reading history in clear graphs. Handy for tracking your own trends, and easy to share with your doctor.
Frequently asked questions
How do I know if heat is affecting my blood pressure? Dizziness or spots in your vision when you stand up, unusual fatigue, a racing heart or a persistent headache are all signs worth taking seriously. If they keep happening, measure your blood pressure and write down the readings. They'll be useful if you need to speak to a doctor.
Should I take my blood pressure medication differently in summer? Don't change your dose on your own. If your blood pressure seems to be behaving differently than usual, or you feel noticeably worse, speak to your doctor. Adjusting treatment in summer is sometimes the right call, but it should always be a medical decision.
When is the best time to measure blood pressure in summer? First thing in the morning, before eating and before taking any medication. That gives you the most reliable reading. During hot spells, it's worth adding an afternoon measurement too, especially if you notice any symptoms.
What counts as a normal blood pressure reading? According to WHO guidelines, normal blood pressure is below 120/80 mmHg. Readings consistently above 140/90 mmHg are considered high blood pressure and should be discussed with a doctor. Before you measure at home, sit quietly for five minutes first. It makes a bigger difference than you'd think.
Summer, under control
You can't change the temperature outside. But knowing how your body is coping and keeping track of your readings, that part you can manage. A blood pressure monitor at home isn't just for people who are ill or elderly. Sometimes one reading is all it takes to know where you stand.
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