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HIGH BLOOD PRESSURE SERIES · ARTICLE 4 OF 12
Understanding your BP reading
What the numbers mean and how to measure at home.
If the first three articles in this series have done their job, you have already had your blood pressure checked at a clinic or pharmacy — or you are planning to this week. This article picks up where that ends. Once you know your BP, what do you do with it?
We are going to walk through what the two numbers actually mean in everyday life, why measuring at home is one of the single most useful things a person with high BP can do, how to choose a monitor in South Africa without spending too much, exactly how to take a reading correctly, and how to keep a simple record that your clinic can actually use.
This article is for two kinds of reader
If you already know you have high BP, this is your daily-management toolkit.
If you do not yet know, but you suspect, this is how to find out for yourself before you ever set foot in a clinic.
The two numbers — a quick refresher
Blood pressure is measured in millimetres of mercury (mmHg) and written as a fraction.
120 / 80 mmHg
The top number is systolic — the pressure when your heart squeezes. The bottom number is diastolic — the pressure when your heart relaxes between beats. The categories from article 1, as a reminder:
Category Top Bottom Normal under 120 and under 80 Elevated 120 – 129 and under 80 Stage 1 high BP 130 – 139 or 80 – 89 Stage 2 high BP 140 or more or 90 or more Crisis (call for help) 180 or more or 120 or more
Both numbers matter. For most adults the top number is the more important one. For people over 65 the bottom number tends to drift down naturally, and the top number is the one to focus on.
Why measure at home at all
A single reading at a clinic is a snapshot. It tells you what your BP was at that moment, under that nurse, in that chair, on that day. Your BP changes constantly through the day — going up after coffee, after climbing stairs, after a stressful phone call; going down when you sleep, when you sit quietly, when you breathe deeply.
Home measurement gives the bigger picture:
• It catches white-coat hypertension — the BP that goes up only in clinics. Home readings show whether that high clinic reading is a real problem or a panicked moment.
• It catches masked hypertension — the BP that is normal in the clinic but high everywhere else. This is the silent killer’s silent killer.
• It shows your medication is working. People who measure at home are far more likely to bring their BP fully under control because they can see, week by week, what’s happening.
• It changes behaviour. The simple act of measuring tends to make people more careful about salt, exercise, and missed tablets.
• It gives your clinic better data. A two-week log of home readings is more useful to a doctor than three clinic readings six months apart.
Studies show that people with high BP who measure at home get to their target numbers an average of three months sooner, and stay there about 25% longer, than people who only measure at the clinic.
How to choose a home monitor
You have three real choices in South African pharmacies. The differences matter.
Upper-arm digital monitor — what we recommend
A cuff that wraps around your upper arm and inflates automatically when you press a button. The screen shows the result a minute later. These are the most accurate, the most reliable, and the easiest to use correctly. Most are battery-powered; some plug into the wall.
Price in South Africa: roughly R400 to R900. Reliable brands you will find at most pharmacies: Omron, Beurer, Microlife, Citizen. Avoid the very cheap, unbranded options — accuracy matters more than saving R150.
What to look for on the box:
• The words “validated” or “clinically validated”
• An upper-arm cuff that fits your arm (most adult cuffs fit 22 – 42 cm — measure around your upper arm before buying)
• Large clear digits — your eyes are not getting younger
• Memory for at least 30 – 60 readings — useful when you take it to clinic
Wrist monitor — usually not worth it
Cheaper and smaller, but much harder to use correctly. The wrist has to be held at exactly heart level for the reading to be accurate; if it is too high or too low, the number is wrong by 10 mmHg or more. They are useful only for people whose upper arms are too large for a standard cuff.
Manual cuff with a stethoscope — for trained users only
Used by nurses and doctors. Not practical for home use unless you have been trained.
Cuff size matters more than brand
A cuff that is too small gives readings that are too high by 5 – 10 mmHg. A cuff that is too large gives readings that are too low by a similar amount. Measure around your upper arm (halfway between elbow and shoulder) before you buy. Most adult monitors come with a “medium” cuff that fits 22 – 32 cm; larger sizes (32 – 42 cm) are available separately and worth buying if you need them.
How to measure properly
This is the step that, more than anything else, determines whether your readings are accurate. The good news is that it is not difficult — but it is more particular than most people realise.
Before you start
• No coffee, tea, cigarettes or exercise in the 30 minutes before the reading.
• Empty your bladder — a full bladder raises BP by about 10 mmHg.
• Sit quietly for at least 5 minutes before the first reading. This is the single most-skipped step.
Position yourself correctly
• Sit in a chair with a back. Feet flat on the floor, not crossed. Legs uncrossed.
• Rest your arm on a table so the cuff is at the same height as your heart.
• The cuff goes on your bare upper arm (roll up your sleeve, or remove the arm of a shirt — do not measure over a thick sleeve).
• The bottom edge of the cuff should sit about 2 cm above the elbow crease.
• Sit still. Do not talk during the measurement. Do not watch TV or scroll on your phone — both can change the reading.
Take the reading
• Press the start button. The cuff will inflate and then slowly deflate.
• Wait a minute, then take a second reading on the same arm. If they are within 5 mmHg of each other, write down the average. If they are more than 10 mmHg apart, take a third reading and average the last two.
• Always use the same arm — most people use their non-dominant arm (the left arm if you are right-handed).
When to measure
For the first two weeks after diagnosis, or when you start a new medication, or when your dose is changed:
• Two readings in the morning, before breakfast and before any medication.
• Two readings in the evening, before dinner.
• Every day, for 7 days. That gives you 28 readings — more than enough for any pattern to show.
Once your BP is stable and well-controlled, less often is fine:
• Two readings, twice a week, at the same times.
• A 7-day burst before each clinic visit, so you have fresh data to bring with you.
Common mistakes that ruin readings
Almost every false reading we hear about comes down to one of these:
• Measuring just after coffee, a cigarette, or a brisk walk. BP rises by 5 – 15 mmHg for half an hour afterwards.
• Measuring with a full bladder. Adds about 10 mmHg.
• Measuring on a sleeve. A thick shirt sleeve under the cuff can add 5 – 50 mmHg of nonsense.
• Talking during the reading. Adds 5 – 15 mmHg. Same for watching news on TV.
• Crossing your legs. Adds about 5 mmHg, occasionally more.
• Arm hanging down or held too high. The cuff must be at heart level. Resting on a table at the right height usually does this naturally.
• Wrong cuff size. Discussed above. The single biggest equipment error.
• Taking only one reading. The first reading of a session is almost always the highest. Average two or three.
Keep a simple record
The point of measuring at home is to share the pattern with your clinic. Most monitors have a memory function, but those tend to be hard to read out and easy to lose. A small notebook works just as well. So does a notes app on your phone, or a printable log.
A useful record looks like this:
Date Time Top Bottom Pulse Note 5 Aug 06:45 138 87 72 before med 5 Aug 18:30 132 84 76 before dinner 6 Aug 06:50 135 86 70 before med 6 Aug 18:45 129 82 74 after walk
The “note” column is the secret ingredient. A reading taken right after climbing the stairs is a different story to one taken first thing in the morning. Knowing what the reading was associated with makes the pattern much clearer to your clinic.
What numbers mean trouble — and what is just a normal wobble
One high reading is not a crisis. BP varies all the time. What matters is the average, the trend, and the size of the spike.
Normal wobble — don’t panic
• A reading 5 – 15 mmHg higher than usual on a stressful day.
• A reading that’s high once and then normal twice on the same day.
• A morning reading slightly higher than the evening reading — this is normal for most people.
If you have a wobble like this, sit quietly for 10 minutes and re-test. Almost always, the second reading is closer to your usual numbers.
Worth a clinic visit this week
• Your average over a week has crept up by more than 5 – 10 mmHg.
• You are starting to see readings above 150 / 95 more than once a week.
• You have been taking your medication, eating carefully, and walking — and the numbers are still not budging.
Go to a clinic or hospital today
If a reading is 180 / 120 or higher, sit quietly for 5 minutes and re-test. If it is still that high — or if you also have chest pain, a bad headache, blurred vision, weakness or numbness on one side of the body, or trouble speaking — get to a clinic or hospital immediately. Call 10177 for an ambulance.
What about the pulse reading?
Most home monitors show your pulse alongside the BP numbers. A normal resting pulse for most adults is 60 – 100 beats per minute. Lower is usually fine if you are fit. Higher is fine briefly after coffee or anxiety. Persistently above 100, or persistently irregular, is worth mentioning to your clinic, especially if you are taking BP medication.
The bigger picture
Measuring at home turns BP from something abstract and frightening into something concrete and manageable. You stop being a passenger and start being the driver. You see, in your own numbers, what salt does to you, what walking does, what stress does, what medication does, what one good night’s sleep does.
It also makes you a better patient. The clinic gets a record of weeks of real readings, not one number taken in a hurry. Your nurse or doctor can adjust treatment based on real life, not on a snapshot.
The next article in the series moves to food: the 10 most affordable South African foods that lower blood pressure, and how to actually use them in everyday meals.
Where to get more help
Heart and Stroke Foundation South Africa — heartfoundation.co.za · 021 422 1586 — for printable BP log templates.
Most pharmacies (Clicks, Dis-Chem, Pick n Pay) — for upper-arm monitors and cuff sizing.
British and Irish Hypertension Society — bihsoc.org — keeps a public list of clinically validated home monitors. Most brands sold in SA pharmacies are on it.
Phila Today High Blood Pressure Series — next: the 10 most affordable South African foods that lower blood pressure.
Phila Today · Article 4 of 12 in the High Blood Pressure Series