High blood pressure: what it is, which values matter, and what to do

If your monitor just read 145/92 and you are reading this with your heart rate up a bit, breathe. An isolated reading is not hypertension. Hypertension is a pattern, not a number.

Let’s put the ideas in order.

What counts as “high”

The classification most widely used in Europe sorts office blood pressure like this. Two caveats before you read it: guidelines do not fully agree with each other — some set the threshold for hypertension lower than this table does — and your own target figure is set by your doctor, not by any table.

Category	Systolic (mmHg)	Diastolic (mmHg)
Optimal	< 120	< 80
Normal	120-129	80-84
High-normal	130-139	85-89
Grade 1 hypertension	140-159	90-99
Grade 2 hypertension	160-179	100-109
Grade 3 hypertension	≥ 180	≥ 110
Hypertensive crisis	> 180 and/or	> 120

These are office values, not home values. At home, numbers run about 5 mmHg lower. If at home you average 135/85, at the clinic you will probably read 140-145/90-95.

Why the top and bottom numbers both matter

The reading has two numbers: systolic (the “high”, when the heart beats) and diastolic (the “low”, when the heart rests). Both matter, but they don’t weigh the same.

• In younger people, a high diastolic figure is usually what catches a doctor’s eye first.
• From around 60 onwards, the systolic figure tends to carry more information, because arteries stiffen with age.

A reading with a high systolic and a normal diastolic — 145/75, say — is a recognised pattern with a name of its own. Like every other pattern here, it is assessed by your doctor over several days of readings, never from a single figure.

Symptoms that are NOT from hypertension

This is important: hypertension produces no symptoms. The fatigue, headache, dizziness or ringing in the ears that many people blame on “blood pressure” do not correlate with actual numbers.

If you have acute symptoms (chest pain, sudden severe headache, blurred vision, confusion, difficulty speaking), do not wait to measure at home. Call emergency services. It could be a hypertensive crisis or a stroke, and every minute counts.

What to do if your average is high

If your average over the last two weeks is 135/85 or higher, book an appointment with your doctor. Don’t go to emergency with one isolated reading from a day. Bring the log (printed or on your phone) and tell them how you measured.

The doctor will decide if you need:

• Lifestyle changes (the five classics: less salt, more vegetables, move, stop smoking, moderate alcohol).
• 24-hour ambulatory monitoring (a cuff that inflates by itself at set intervals through the day and the night).
• Starting or adjusting medication.

What NOT to do

• Don’t medicate yourself. Taking a relative’s blood pressure pills can drop your pressure dangerously low: the drug and the dose were worked out for someone else.
• Don’t ignore a high average. Untreated high blood pressure is one of the main risk factors for stroke.
• Don’t obsess over an isolated reading. Numbers vary throughout the day. What matters is the trend.

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If you want a log that lets you see the trend, NurseAI stores every reading with its date and time, draws the trend as a moving median instead of reacting to isolated readings, and exports a monthly PDF you can print for the appointment. It is free, works offline and needs no account. The beta opens soon, sign up here.

To carry on: what the two blood pressure numbers mean and how to measure blood pressure correctly at home.

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Note: this article is general information and does not replace professional advice. NurseAI is a log and a summary to bring to your doctor: it is not a medical device, it does not diagnose and it does not recommend doses. For any question about your health or your medication, always ask your doctor. If you have severe symptoms, seek urgent medical care.