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What is hypertension (high blood pressure)?

To understand high blood pressure, you must first understand what blood pressure is. Very simply, this refers to the force of blood against the walls of your arteries. Think of this as water rushing through a pipe.

High blood pressure can cause damage to the walls of your arteries. This can create scarring, which in turn causes fatty plaque to build up, contributing to the narrowing and blocking of your arteries. Your heart will become strained and weakened. Blood vessels in your brain can burst – causing a stroke – if your blood pressure is very high.

Your blood pressure varies during the day, moving up and down, often linked to activity or the lack of it (for example, your blood pressure is usually lowest at night but rises quite quickly once you get out of bed in the morning).

Everyone’s blood pressure goes up occasionally if, for example, something has frightened you, or you are angry or feeling stressed. But when your blood pressure remains high for long periods of time it means you have high blood pressure. This is also referred to as hypertension, a term you may hear your doctor use.

Systolic and diastolic: what the numbers mean

Blood pressure is measured with two numbers – systolic and diastolic. The systolic is an indication of how much pressure there is in the arteries (the maximum amount) when the left ventricle of the heart contracts. The diastolic indicates what the pressure is in your arteries between heartbeats.

There are several categories of blood pressure levels, which are all measured as mmHg (millimetres of mercury). Let’s look at some numbers:


Systolic (mmHg)

Diastolic (mmHg)


Below 120

Below 80


Below 130

Below 85

High-normal (prehypertension)



High blood pressure — if measured by healthcare professional

Above 140

Above 90

High blood pressure — if measured at home

Above 135

Above 85

High blood pressure — if you have diabetes or chronic kidney disease

Above 130

Above 80

High blood pressure is referred to as the “silent killer”, because it often has no symptoms. This is why regular check-ups with your doctor are a good idea.

To learn more about symptoms, read Your blood pressure: the one number that could save your life.

What is prehypertension?

We previously showed you the numbers (systolic and diastolic) that would indicate prehypertension: 130-139 mmHg (systolic) or 85-89 mmHg (diastolic). This is sometimes also referred to “high-normal” blood pressure.

According to the Heart and Stroke Foundation, 1 in 5 Canadians (or about 20% of adults) have high blood pressure; another 1 in 5 have blood pressure in the high-normal range. Hypertension Canada adds that more than half of those in the high-normal category will develop hypertension within 5 years — unless they make changes.

If you have high-normal blood pressure, you might be headed towards a situation where you will need medications for life. But by making lifestyle changes, you can get your blood pressure down to a safe range – and then by keeping it at this level, you can delay your chances of developing high blood pressure for many years.

Living well with high blood pressure

Here are some easy ideas that will help you lower and maintain your blood pressure, help you feel better and may even save you money!

  • Eat well
    • Try to eat more fresh foods, particularly fruits and vegetables. Select those that are high in potassium but low in sodium – like bananas, cantaloupe, and nectarines, asparagus, broccoli, and potatoes.
    • Check the labels for fat content, sugar content, and sodium. Try to eat foods that have less than 120 mg or less than 5% Daily Value (DV) of sodium per serving.
    • Don’t eat foods that contain a lot of salt – like crackers, chips, processed lunchmeats, or some pickled foods.
    • Don’t use sauces (like ketchup or seafood sauce) as often.
    • Eat at home more often, and avoid fast food restaurants.
    • Don’t add salt  while you’re cooking, or at the table.
    • To flavour your food, use other spices in place of salt. Lemon or lime juice, fresh garlic, and a splash of wine – all make good substitutes.
    • Choose grains and grain products.
    • Eat lean meats, fish, and poultry.
    • Emphasize low fat or non-fat dairy products.
  • Get physical. Exercise regularly. Talk to your doctor about an exercise program that is right for you, pick an exercise program that appeals to you, and ask a friend to join you.

  • Watch your weight. Even a weight loss of 8-10 lbs can lower your blood pressure significantly. Keep an eye on your BMI and waist circumference. Read Obesity and cardiovascular risk for more information.

For more information and support, search “hypertension” in Find Support for organizations in your area.

What is hypertension?