The cuff tightens around your arm, the machine starts humming and you sit there trying very hard to relax. Then the doctor reads out two numbers that are higher than you expected, and relaxing suddenly gets a lot harder.
The first time that happened to me, I wanted to know what those two numbers actually meant, and whether a reading taken while I was sitting nervously in a clinic really reflected my normal level. It turns out there’s a good reason to ask. Blood pressure changes throughout the day, rising with exercise, stress or pain and falling when you rest, and plenty of people find it runs higher at the doctor’s surgery than it does at home.
So what is high blood pressure, what causes it, and how do you know whether a reading is something to worry about? Along the way, I also found out that Australia and the United States don’t even agree on where “high” begins.
What is blood pressure?
Every time your heart beats, it pushes blood into your arteries, and as that blood travels around your body it presses against the artery walls. That pressure is your blood pressure. A reading is written as two numbers, such as 120/80 mmHg, measured in millimetres of mercury, a unit left over from the original mercury-filled instruments.
The top number is your systolic pressure, the pressure in your arteries when your heart contracts and pumps blood. The bottom number is your diastolic pressure, the pressure while your heart relaxes between beats. The instrument that measures them has a wonderfully unwieldy name, the sphygmomanometer, although most people just call it a monitor. Modern ones use an inflatable cuff around the upper arm and an electronic sensor.
Your reading isn’t a fixed number. It changes with what your body is doing, and stress, activity and your general health all affect it. It also follows a daily pattern as part of your circadian rhythm, generally dropping while you sleep and rising as you become active. That’s why one reading on its own rarely tells the whole story.
What is considered high blood pressure in Australia?
In Australia, high blood pressure, or hypertension, is generally defined as a reading of 140/90 mmHg or higher. That means your systolic pressure is 140 or above, your diastolic pressure is 90 or above, or both. The Heart Foundation’s guideline also recognises some lower categories:
| Reading (mmHg) | Australian category |
|---|---|
| Less than 120/80 | Optimal |
| 120-129 / 80-84 | Normal |
| 130-139 / 85-89 | High-normal |
| 140/90 or higher | High blood pressure |
These numbers are a general guide. Your doctor will interpret your readings in the context of your age, medical history and overall risk of heart disease and stroke. A single high reading doesn’t automatically mean you have hypertension, which is why Healthdirect describes it as readings that are consistently above 140/90, and why repeated measurements are usually needed to confirm it.
Why does the US use 130/80?
This part of the topic confuses a lot of people, and it surprised me. Search online and you may find an American chart saying 130/80 is already hypertension, while an Australian source says high blood pressure starts at 140/90. Both are correct, because they follow different clinical guidelines.
The 2025 American Heart Association and American College of Cardiology guideline classes a top number of 130-139 or a bottom number of 80-89 as stage 1 hypertension, and anything from 140/90 up as stage 2, as the Preventive Cardiovascular Nurses Association summarises. It also weighs a person’s overall cardiovascular risk when deciding whether to start medication.
Australia uses the 140/90 threshold, again weighing cardiovascular risk and other factors in deciding how someone should be managed. An updated Australian guideline is also due later in 2026, according to newsGP, from the Royal Australian College of General Practitioners (RACGP), so the local picture may shift.
So a reading of 135/85 would be “high-normal” to an Australian GP and “stage 1 hypertension” to an American one. It’s a good reminder that medical definitions are decisions made by experts weighing the evidence, not lines drawn by nature. It’s worth checking where an online chart comes from before comparing it with what your GP tells you.
Why is your blood pressure higher at the doctor’s?
If your readings are normal at home but consistently higher when you visit the doctor, there’s a name for it: white coat hypertension. It describes pressure that’s raised in a medical setting but lower when measured anywhere else. It’s common to feel stressed or anxious when a health professional takes the measurement, and because stress pushes your pressure up, a clinic reading can be higher than your real, everyday figure. A 2025 review in the journal Cureus puts it at around one in five people whose clinic readings come back high.
Nerves aren’t the only thing that can inflate a reading. It may be temporarily higher if you’ve recently exercised, rushed to get to your appointment, had caffeine or a cigarette, or are in pain or stressed. Talking during the measurement, not sitting quietly beforehand and even having a full bladder can all nudge the numbers up as well.
It’s tempting to write white coat hypertension off as “just nerves”, but researchers aren’t convinced it’s completely harmless. A long-running Italian study called PAMELA followed more than 1,400 people for 10 years. According to the European Society of Cardiology’s summary, 43% of those with white coat hypertension had progressed to sustained high blood pressure. That’s about 2.5 times the risk of people whose readings were normal everywhere.
That’s one reason your doctor may ask you to monitor at home, which gives a much better picture of what’s happening during a normal day. Healthdirect says doctors often ask for readings twice a day, morning and evening, for seven days. Some people are also asked to wear a 24-hour ambulatory monitor, which records readings through the day and night while you go about your usual routine.
So if your numbers always seem higher at the GP, don’t just assume the machine is wrong. Tell your doctor what you’re seeing at home, because comparing readings from different settings is exactly how they work out what’s really going on.
Why does high blood pressure matter?
One of the tricky things about hypertension is that you usually can’t feel it. Most people with it have no obvious symptoms, so there’s no reliable way to tell whether yours is elevated just by how you feel. Over time, though, consistently high pressure puts extra strain on the heart and blood vessels. Healthdirect explains that it increases your chances of developing heart disease, stroke, chronic kidney disease and eye disease, among other conditions.
It’s also far more common than most of us assume. The Australian Institute of Health and Welfare’s (AIHW) Hypertension in Australia report estimates that 39% of Australian adults had hypertension in 2022, roughly 7.2 million people. Notably, 63% of those adults didn’t report having the condition, which suggests many of them simply didn’t know, and only about 40% had it under control.
What causes high blood pressure?
There usually isn’t one simple cause. For most people, hypertension develops gradually as age, genetics, lifestyle and other health factors combine over the years. Some of those factors can’t be changed: getting older and having a family history of hypertension both increase your risk. Others can, including carrying extra weight, not getting enough physical activity, eating a diet high in salt, drinking more alcohol than recommended and smoking.
In some people, there’s a more specific underlying cause, such as kidney disease, narrowing of the arteries that supply the kidneys, hormonal conditions, certain medicines or drugs, sleep apnoea or complications of pregnancy. This is known as secondary hypertension, because another condition is driving it, and treating that condition can bring the pressure back down.
Can you lower your blood pressure?
Often, yes. The same lifestyle factors that push your pressure up are also the levers for bringing it down, and changing them can help prevent hypertension as well as manage it once you have it. The 2025 US guideline treats lifestyle changes as the first line for all adults.
- Stay physically active. Regular activity helps lower your pressure and improves your overall heart health. You don’t need an intense program; walking, cycling and swimming all count. If you have an existing health condition or haven’t exercised for a while, check with your doctor about what level of activity suits you.
- Watch your weight. Carrying extra weight increases the risk of hypertension, and if you’re overweight, losing some of it can improve your readings along with other aspects of your heart health.
- Cut back on salt. A diet high in sodium contributes to hypertension, and most of the salt in the Australian diet comes from processed and packaged foods such as bread, sauces and ready meals rather than the salt shaker. Checking food labels and choosing less processed foods makes a real difference.
- Get enough sleep. Poor sleep and conditions such as sleep apnoea are linked with high readings. If you snore heavily, stop breathing during sleep or feel unusually tired during the day, it’s worth raising with your doctor.
- Manage stress. Stress raises your pressure in the moment, and ongoing stress makes healthy habits harder to keep up. Finding ways to manage it, alongside sleeping well and staying active, is a useful part of looking after your heart.
Alcohol and smoking
The National Health and Medical Research Council (NHMRC) alcohol guidelines recommend that healthy adults drink no more than 10 standard drinks a week and no more than 4 on any one day, and note that the less you drink, the lower your risk. Smoking damages blood vessels and adds to cardiovascular risk on top of raised pressure, so if you smoke, quitting brings substantial health benefits at any age. Your GP or the Quitline on 13 78 48 can help.
Lifestyle changes aren’t always enough on their own. Some people also need medication, and the right treatment depends on their individual circumstances and overall risk, which is a conversation to have with a GP.
How to check your blood pressure at home
If your doctor has asked you to monitor at home, technique matters. Healthdirect recommends sitting quietly for five minutes first, with your feet flat on the floor, legs uncrossed and your back and arm supported. Avoid caffeine and smoking for 30 minutes beforehand, empty your bladder, and take two readings a minute apart.
Use an automatic upper-arm monitor with a cuff that fits properly. Wrist and finger monitors aren’t recommended, and a pharmacist can help you choose a clinically validated model, such as one on the list kept by the University of Tasmania’s Menzies Institute.
Try to take your readings under similar conditions each time, ideally at around the same time each morning and evening. That makes it much easier for you and your doctor to see whether your pressure is genuinely changing, rather than just reacting to what you were doing beforehand. And don’t rely on a smartwatch as a substitute: the 2025 US guideline specifically recommends against cuffless devices until their accuracy improves.
So, what is high blood pressure?
It’s the force of blood pushing against your artery walls being consistently too high, recorded as two numbers: systolic pressure when your heart contracts, and diastolic pressure when it relaxes. In Australia, 140/90 mmHg or higher is considered high, while the US draws the line at 130/80, and your doctor will look at repeated readings and your overall health rather than a single number. Many people find their readings are higher at the doctor’s thanks to white coat hypertension, which is why home monitoring is so useful.
Hypertension is common, affecting around 2 in 5 Australian adults, and it usually has no symptoms, so regular checks are the only way to know. The good news is that staying active, keeping to a healthy weight, cutting back on salt, limiting alcohol and not smoking all help.
Everyone’s numbers and risks are different, so treat this as a starting point rather than a diagnosis. If you’re worried about your readings, or you keep getting high results at home or at the doctor’s, book in with your GP to talk them through.
Sources
- Healthdirect: High blood pressure (hypertension)
- Healthdirect: What is a healthy blood pressure?
- Healthdirect: Blood pressure monitoring at home
- Australian Institute of Health and Welfare: Hypertension in Australia (2026)
- Royal Australian College of General Practitioners, newsGP: Australian hypertension control rates still lag (2026)
- Preventive Cardiovascular Nurses Association: Putting updated blood pressure guidelines into practice (2025)
- Cureus: White coat hypertension in primary care, a narrative review (2025)
- European Society of Cardiology: White-coat hypertension, not so innocent
- National Health and Medical Research Council: Australian guidelines to reduce health risks from drinking alcohol