High blood pressure, also called hypertension, is one of the most common health conditions in North America. In the United States, nearly half of adults have it, and in Canada roughly one in four adults has been diagnosed. Many more don't know they have it, because high blood pressure usually causes no symptoms at all. That's why it's often called the "silent killer."
The good news: your blood pressure is easy to measure, and once you understand your numbers you can work with your doctor to keep them in a healthy range. Here's what those numbers mean.
The two numbers in a blood pressure reading
A reading is written as two numbers, for example 128/82 mmHg (millimetres of mercury).
- Systolic (top number): the pressure in your arteries when your heart beats and pushes blood out.
- Diastolic (bottom number): the pressure in your arteries between beats, when the heart is resting and refilling.
Both numbers matter. After about age 50, the systolic number tends to rise as arteries stiffen, and it becomes an especially important marker of heart and stroke risk.
Blood pressure chart: normal to stage 2 hypertension
These are the categories used by the American Heart Association for adults:
| Category | Systolic (top) | Diastolic (bottom) | |
|---|---|---|---|
| Normal | Less than 120 | and | Less than 80 |
| Elevated | 120–129 | and | Less than 80 |
| Stage 1 hypertension | 130–139 | or | 80–89 |
| Stage 2 hypertension | 140 or higher | or | 90 or higher |
| Severe (hypertensive crisis) | Higher than 180 | and/or | Higher than 120 |
Canadian guidelines use slightly different cut-offs for diagnosis. A doctor's office reading of 140/90 or higher, or an average home reading of 135/85 or higher, is generally considered high. Either way, the direction is the same: the lower your numbers are within the healthy range, the less strain on your heart and blood vessels.
One high reading does not mean you have hypertension. Blood pressure changes through the day with activity, stress, caffeine and even a full bladder. A diagnosis is based on several readings taken on different days, which is why home monitoring is so useful.
Why high blood pressure matters for your heart
When the pressure inside your arteries stays high, your heart has to work harder with every beat. Over months and years this extra workload can:
- thicken and stiffen the heart muscle, especially the left ventricle;
- damage the smooth inner lining of the arteries, making it easier for plaque to build up;
- raise the risk of heart attack, heart failure and stroke;
- strain the small blood vessels in the kidneys and eyes.
High blood pressure is one of the leading risk factors for cardiovascular disease worldwide. Keeping it in a healthy range is one of the most effective things you can do for long-term heart health.
Common risk factors
- Age (risk rises steadily after 40)
- Family history of high blood pressure
- A diet high in sodium and low in potassium
- Carrying extra weight, especially around the waist
- Low physical activity
- Regular heavy drinking
- Smoking
- Ongoing stress and poor sleep, including sleep apnea
- Diabetes or kidney disease
You can't change your age or genes, but most of the other factors on this list respond to everyday habits. See our guide to 9 research-backed habits that support healthy blood pressure.
When a reading is an emergency
If your reading is higher than 180/120, wait five minutes and measure again. If it is still that high and you have chest pain, shortness of breath, back pain, numbness or weakness, changes in vision, or trouble speaking, call 911 right away. These can be signs of a hypertensive emergency, heart attack or stroke.
If the second reading is still above 180/120 but you feel fine, contact your doctor promptly.
What to do with your numbers
- Know your baseline. Take readings at home in the morning and evening for a week and share the average with your doctor.
- Look at your daily habits. Salt, potassium, movement, alcohol, sleep and stress all play a role.
- Follow your doctor's advice. If you've been prescribed medication, keep taking it as directed. Lifestyle changes and supplements are meant to work alongside medical care, not replace it.
- Consider natural support. Many people also look to traditional herbs such as hawthorn and garlic. Learn more in Herbs for high blood pressure: the ingredients in Alistrol.
Looking for natural blood pressure support? Alistrol is a herbal formula registered by Health Canada (NPN 80047013) with daikon seed, holly leaf, aged garlic, hawthorn berry and fulvic minerals. It has been clinically studied in an 8-week, double-blind, placebo-controlled trial, and made in Canada since 2009.
This article is general information, not medical advice. Talk to your doctor or pharmacist before starting any supplement, especially if you take blood pressure medication, and never stop or change a prescribed medication without medical advice.