What Is High Blood Pressure? Numbers, Causes and What to Do
High blood pressure, also called hypertension, means the force of blood pushing against your artery walls stays higher than it should over a long period. It is common, it usually causes no symptoms, and it is one of the main risk factors for heart attack, stroke and kidney disease.
The reason it matters so much is that most people who have it do not know. The only reliable way to find out is to measure it.
What the two numbers mean
A blood pressure reading always has two numbers, written as one over the other, for example 118/76 mmHg.
- Systolic (the top number) is the pressure while your heart is contracting and pushing blood out.
- Diastolic (the bottom number) is the pressure while your heart is relaxed and refilling between beats.
mmHg stands for millimetres of mercury, which is the unit used because the first pressure gauges used a mercury column.
Blood pressure ranges
| Category | Systolic | Diastolic | |
|---|---|---|---|
| Normal | Below 120 | and | Below 80 |
| Elevated | 120 to 129 | and | Below 80 |
| Stage 1 hypertension | 130 to 139 | or | 80 to 89 |
| Stage 2 hypertension | 140 or higher | or | 90 or higher |
| Hypertensive crisis | Higher than 180 | and/or | Higher than 120 |
Notice the words “and” and “or”. For stage 1 and stage 2, only one of the two numbers has to be in that range for the reading to count.
A hypertensive crisis needs immediate medical attention, not a wait and see approach.
Why one high reading does not mean you have hypertension
Blood pressure moves constantly. It rises when you are stressed, when you have just climbed stairs, after coffee, and often simply because you are sitting in a clinic, which is common enough to have a name: white coat hypertension.
A diagnosis is based on several readings taken on different days, usually in a calm state. If a single reading at a pharmacy machine comes back high, that is a reason to measure again properly, not a reason to panic.
How to measure it properly at home
- Sit quietly for five minutes first, with your back supported and feet flat on the floor.
- Rest your arm on a table so the cuff is level with your heart.
- Do not talk during the measurement. Talking can add several points.
- Avoid caffeine, exercise and smoking for 30 minutes beforehand.
- Empty your bladder first. A full bladder raises the reading.
- Take two or three readings a minute apart and record them all.
An upper arm cuff is more reliable than a wrist device. Whatever you use, take it to a clinic once to check it against their equipment.
What causes high blood pressure
In the large majority of cases there is no single identifiable cause. This is called primary hypertension, and it develops gradually over years. The factors that push it up include:
- Age, as arteries naturally stiffen
- Family history
- Carrying excess weight
- A diet high in salt and low in potassium
- Low physical activity
- Regular heavy alcohol use
- Smoking
- Poor or short sleep, including untreated sleep apnoea
- Long running stress
A smaller number of cases are secondary hypertension, caused by something specific such as kidney disease, thyroid problems, certain medicines or sleep apnoea. These can sometimes be reversed by treating the underlying cause.
What the symptoms are
For most people, nothing at all. This is why hypertension is often called a silent condition, and why screening matters more than waiting for a sign.
Very high readings can produce headaches, nosebleeds, shortness of breath or visual changes, but these appear late and are not reliable warning signs. Anyone relying on how they feel to judge their blood pressure is relying on nothing.
What actually lowers it
Lifestyle changes work, and the effect sizes are meaningful rather than token.
- Reducing salt. Most salt in a typical diet comes from processed and restaurant food rather than the salt shaker.
- Regular activity. Around 30 minutes of brisk walking on most days has a measurable effect.
- Losing excess weight. Even a modest loss helps.
- Cutting back alcohol.
- Improving sleep. Short and broken sleep both raise blood pressure, which is covered in our guide on how to get good sleep.
- More potassium from vegetables, beans and fruit, unless a doctor has told you to limit it because of kidney issues.
Where lifestyle alone is not enough, medication is added. These are usually taken long term, and stopping them because the numbers improved is a common and risky mistake, since the numbers improved because of the medication.
Frequently asked questions
What is a normal blood pressure by age?
The targets are not set by age for most adults. Below 120/80 is considered normal whether you are 25 or 65. Older adults often have higher readings, but that reflects how common hypertension becomes, not a different healthy target.
Which number matters more?
Both are used, but above roughly age 50 the systolic number is generally the stronger predictor of cardiovascular risk, because arteries stiffen with age.
Can high blood pressure be cured?
Primary hypertension is managed rather than cured. It can often be controlled to normal levels, and some people control it with lifestyle alone. Secondary hypertension can sometimes resolve if the underlying cause is treated.
Does drinking water lower blood pressure?
Staying hydrated supports normal circulation, but drinking water is not a treatment for hypertension. Severe dehydration can actually raise blood pressure.
Is 130/85 high?
Under current categories, 130/85 falls into stage 1 hypertension because the systolic number is 130 or above. It is worth repeat measurements and a conversation with a doctor rather than immediate alarm.
How quickly can it come down?
Reducing salt and alcohol can show an effect within a couple of weeks. Weight loss and fitness changes take longer, usually a few months.
This article is general information, not medical advice. Readings, targets and treatment decisions should be discussed with a doctor who knows your history.
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