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How to measure your blood pressure at home

The question

Your GP has checked your blood pressure and asked you to keep track of it at home. So you bought a monitor.

Now it gives you a different answer every time you use it. Some readings worry you. Others look fine.

Which one do you write down?

The short answer

None of them on their own. One reading is not a measurement.

Blood pressure goes up and down all day. Any single number tells you about one moment, not about your usual pattern.

What your GP can work with is the average of a week's readings, taken at the same times each day with your arm supported at heart height. At home, that average counts as high once it reaches 135/85 — a lower number than the 140/90 used at the surgery.

Why it matters

Your blood pressure changes constantly. It moves when you walk, talk, need the toilet, feel cold, or sit in a waiting room. That last one even has a name — the white coat effect — and it is a normal body response, not a mistake by the person taking the reading.

Because of this, a reading taken in a clinic is a starting point rather than an answer, and Australian guidelines are built around that. When a clinic reading is high, the next step is to check your blood pressure at home or with a 24-hour monitor. Readings taken outside the clinic are better at predicting long-term health. High blood pressure is also diagnosed over two or more separate visits, never from one result.

So if your doctor has asked you to measure at home, that is the guideline being followed. Your readings are not a second opinion. They are the next part of the check, and the decision depends on how good they are. Careless readings are worse than none: a number that looks reassuring can delay something that needed attention, and one that looks alarming can cause weeks of worry before your next appointment clears it up.

What the evidence says

Three things matter more than most people realise.

Where you put your arm changes the number. In one trial, resting your arm in your lap has been shown to add about 4 points to the top number, compared with resting it on a table at heart height. Letting your arm hang by your side added about 6.5 points.

Where you rest your arm changes the reading

Systolic difference compared with an arm supported at heart height.

Heart level Forearm on a table Cuff level with the heart Reference Below Hand resting in your lap Cuff sits below the heart +3.9 mmHg Lowest Arm hanging by your side Cuff furthest below the heart +6.5 mmHg

From a randomised crossover trial comparing arm positions in the same people. Below heart level, gravity adds pressure at the cuff, so both of these positions read high — and the hanging arm, lowest of the three, reads highest. Whichever position you use, sit still for five minutes first, with your feet flat and your back supported.

That is not a rounding error. It is the difference between 138 and 145 — one side of the line and the other, from nothing but where your arm was.

The cuff has to fit. A cuff that is the wrong size for your arm can shift the reading by several points in either direction. If your arm is on the larger or smaller side, you may need a different cuff from the one in the box.

Your first readings are the least useful. Australian expert guidance recommends throwing out your whole first day of readings before working out the average. Early readings tend to run high while you are getting used to the cuff and watching the screen closely.

What to do

Here is the routine Australian guidelines set out. Every step is there because it changes the number.

Before you start

  • Use an automatic monitor with a cuff that goes around your upper arm. Not a wrist one. Not a finger one.
  • Check the cuff fits your arm within the range printed on it.
  • Wait 30 minutes after coffee or a cigarette. Don't measure straight after food, medication or exercise.
  • Go to the toilet first.

Sitting down

  • Sit quietly for five minutes. No talking, no phone, no TV.
  • Feet flat on the floor. Legs uncrossed.
  • Back supported by the chair.
  • Bare upper arm. Not over a sleeve, and not with a sleeve rolled into a tight band.
  • Arm resting on a table, at about the height of your heart. Not in your lap. Not hanging by your side.

Taking the readings

  • Take two readings, one minute apart. Do this in the morning and again in the evening.
  • Same times each day, before your medication and before food.
  • Keep going for seven days. Five is the minimum.
  • Leave out day one completely. Average everything after that.

One number worth knowing. At home, an average of 135/85 or higher is the level Australian guidelines use. That is lower than the 140/90 most people associate with the doctor's surgery. Home readings sit lower, so they are judged against a lower number. Comparing your home average with a clinic number is an easy way to frighten yourself for no reason — or to feel reassured when you shouldn't be.

What to watch for

The mistakes we see most often.

  • Averaging three readings from one sitting. Three readings is what happens at a clinic visit. At home, your GP needs the pattern across a week. Both are right, for different places.
  • Only measuring when you feel unwell. You end up with readings from your worst moments and nothing to compare them with.
  • Taking it again until you get a number you like. Very human, and it quietly ruins the average.
  • Measuring over your clothes. A sleeve pushed up above the cuff can squeeze your arm.
  • Using a wrist monitor because it is easier. Wrist monitors are much more affected by position, and Australian guidance says to use an upper-arm cuff.
  • Only writing down the readings you remember. Use the monitor's memory, or write each one down as you go.

When to get help

Take the whole week's readings to your GP, rather than a single number. A full set is what the guidelines are designed around, and it gives them something solid to work from.

Alongside whatever your doctor recommends — including medication, if you need it — what you eat changes blood pressure. The research is clear on four things.

  • The eating pattern matters most. The DASH pattern — vegetables, fruit, wholegrains, legumes, nuts and reduced-fat dairy, with less salt, saturated fat and added sugar — lowered the top number by about 3 points across 30 trials in 5,545 adults. It worked whether or not people already had high blood pressure.
  • Body weight. Losing weight lowers the top number by roughly 1 point for each kilogram lost.
  • Alcohol. Drinking less lowers blood pressure, mainly for people currently drinking more than about two standard drinks a day.
  • These problems travel together. High blood pressure often turns up alongside high cholesterol, high blood sugar and extra weight around the middle. A change aimed at one of them often improves the others at the same time.

Knowing where to start is the hard part

Research tells you what works for most people. It does not tell you what to cook on Tuesday night, or which of those four matters most for you.

That is the part Cardiovascular Dietetics does. We look at what you are eating now, the conditions you have, and the research above, and find where the gaps are. Then you change the few things likely to make the biggest difference, instead of everything at once.

We work alongside your GP and specialists, not separately from them. If you have a chronic disease management plan, dietitian visits can be part of it — worth asking about at your next appointment. The Cardiovascular Dietetics Online Clinic sees clients anywhere in Australia.

This article is general information, not personal advice. It cannot tell you what your readings mean. Please talk them through with your GP or dietitian, and never change or stop medication based on a home monitor.

References
  1. Sharman JE, Howes FS, Head GA, et al. Home blood pressure monitoring: Australian Expert Consensus Statement. Journal of Hypertension. 2015;33(9):1721–1728. doi:10.1097/HJH.0000000000000673
  2. Liu H, et al. Arm Position and Blood Pressure Readings: The ARMS Crossover Randomized Clinical Trial. JAMA Internal Medicine. 2024;184(12):1436–1442. doi:10.1001/jamainternmed.2024.5213
  3. 2023 ESH Guidelines for the management of arterial hypertension. Journal of Hypertension. 2023. doi:10.1097/HJH.0000000000003480
  4. National Heart Foundation of Australia. Guideline for the diagnosis and management of hypertension in adults — 2016. Melbourne: NHFA, 2016.
  5. Filippou CD, Tsioufis CP, Thomopoulos CG, et al. Dietary Approaches to Stop Hypertension (DASH) Diet and Blood Pressure Reduction in Adults with and without Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Advances in Nutrition. 2020;11(5):1150–1160. doi:10.1093/advances/nmaa041
  6. Neter JE, Stam BE, Kok FJ, Grobbee DE, Geleijnse JM. Influence of weight reduction on blood pressure: a meta-analysis of randomized controlled trials. Hypertension. 2003;42(5):878–884. doi:10.1161/01.HYP.0000094221.86888.AE
  7. Roerecke M, Kaczorowski J, Tobe SW, et al. The effect of a reduction in alcohol consumption on blood pressure: a systematic review and meta-analysis. Lancet Public Health. 2017;2(2):e108–e120. doi:10.1016/S2468-2667(17)30003-8
  8. Alberti KGMM, Eckel RH, Grundy SM, et al. Harmonizing the metabolic syndrome: a joint interim statement. Circulation. 2009;120(16):1640–1645. doi:10.1161/CIRCULATIONAHA.109.192644
  9. Meiyan S, Zheng J, Ying W, Wen C, Kaizu X, Lin L. Influence of cuff size on the accuracy of supine blood pressure measurement. Blood Pressure Monitoring. 2025;30(4):169–174. doi:10.1097/MBP.0000000000000752