Blood pressure is the result of circulating blood exerting pressure against the walls of your arteries. This pressure is very important because it allows the blood to flow through the arteries and deliver nutrients to all the organs of your body. Blood pressure is determined by the amount of blood your heart pumps and the amount of resistance to blood flow in your arteries. The more blood your heart pumps and the more narrow your arteries, the higher your blood pressure.
Your blood pressure is recorded as two numbers (for example, 124/85 mm Hg, as shown in the graphic). The top number is the systolic and the bottom the diastolic. These values are measured in millimeters of mercury (mm Hg).
- The systolic value represents your heart “at work,” the pressure exerted when your heart beats and fills your arteries with blood.
- The diastolic value represents your heart “at rest,” between beats. During this phase, your heart fills with blood in advance of the next beat.
Optimal blood pressure is a reading of lower than 120/80. When your blood pressure numbers are consistently greater than 135/85, you’re considered to have high blood pressure, or hypertension (but if you have diabetes or kidney disease, 130/80 is considered a high reading).
In addition to your normal, or “ideal,” blood pressure values, there are three categories of blood pressure — hypertension, pre-hypertension, and hypotension — each of which has a different impact on your health.
Hypertension, or high blood pressure, is present when there are consistent measures that exceed 135/85 (or readings higher than 130/80 for people with diabetes or kidney disease). This indicates that to reduce your risk of developing a serious condition, like heart disease, you should make significant lifestyle changes, including even medication, to lower your blood pressure.
High blood pressure, or hypertension, makes your heart work a lot harder and, while doing so, causes excess force on your artery walls. Any added force can damage arteries and increase your risk of developing cardiovascular disease.
High blood pressure contributes to cardiovascular disease through the scarring of artery walls where plaque can build up and narrow the vessels. This causes a type of cardiovascular disease known as coronary artery disease. A narrowing artery can become completely blocked, leading to a heart attack. Also, plaques can break away from the artery wall and cause a blockage elsewhere.
High blood pressure has been called the silent killer because it often has no warning signs or symptoms.
People with high blood pressure are often not aware they have it until they are diagnosed by a health care professional. You could have high blood pressure for years without knowing it, putting you at greater risk for cardiovascular disease and organ damage. If damage has occurred, you may have symptoms that include:
- Shortness of breath
Pre-hypertension indicates you have slightly surpassed the ideal target values and are at increased risk of developing high blood pressure, which may require medical therapy. If your systolic blood pressure is between 120 and 135 and/or your diastolic is between 80 and 85, you should take the necessary steps to decrease your blood pressure
Hypotension, otherwise known as low blood pressure, is a reading of less than 90/60. It can be just as serious and dangerous as high blood pressure and should not be ignored. Hypotension indicates that the force of your blood flow is inadequate, and this could mean certain of your vital organs are not receiving enough blood. Hypotension is a medical concern only if it causes signs or symptoms or is linked to a serious condition, such as heart disease. People who take certain high blood pressure medications, such as diuretics, have an increased risk for low blood pressure.
What is considered low blood pressure may vary from person to person. Low blood pressure can be considered “normal pressure” to some people who have low blood pressure all the time. In this case, they have no signs or symptoms. Symptoms of hypotension may include:
- Cold and sweaty or clammy skin
- Blurry vision
There are some risk factors you cannot control, and these put you at greater risk for high blood pressure (hypertension). They include:
- Age: About 50% of people older than the age of 65 have high blood pressure
- Family history of high blood pressure
- Ethnicity: High blood pressure is more common among people who are of African, South Asian, or First Nations descent.
- Gender: The risk for women increases after menopause, putting them in even greater jeopardy than men.
What causes high blood pressure?
There are two main types of high blood pressure:
1. Primary Hypertension (also known as “essential hypertension”): Cases in which there is no easily identifiable cause for high blood pressure. The risk of developing essential hypertension increases with age. A number of lifestyle factors can increase the risk for essential hypertension, including:
- Getting too much salt in the diet
- Drinking alcohol excessively (males no more than two drinks a day; females one drink a day)
- Being overweight
- Getting insufficient exercise
- Experiencing unmanageable stress
2. Secondary Hypertension: Cases in which high blood pressure does have an identifiable cause. Common causes of secondary hypertension include:
- Kidney disease
- Hormone disorders
- Some drugs (such as birth control pills and nonsteroidal anti-inflammatory drugs)
- Sleep apnea (repeated, short stops in breathing while sleeping)
- Arteriosclerosis (hardening of the arteries)
How is blood pressure diagnosed?
Blood pressure is diagnosed by a doctor using a blood pressure machine. The process includes:
- Being seated in a chair with your back supported
- Putting your feet flat on the floor and supporting your arm at heart level
- Remaining quiet for five minutes and refraining from talking
It is very important to use the proper size cuff when taking a blood pressure reading. Failure to do so will lead to inaccuracies. A cuff that is too small for the arm circumference will give an artificially high reading. A cuff that is too large will give too low a reading. Initially, blood pressure should be measured in each arm to make sure both readings are the same. The arm with the higher readings should then be targeted for all future blood pressure checks.
If your blood pressure readings are high, your doctor may ask that you return for additional measurements on different days because blood pressure can vary widely from day to day.
Your doctor will most likely diagnose you with high blood pressure if you have several readings of 140/90 or higher. If you have readings of 130/80 or higher and are diabetic or have chronic kidney disease, you are likely to be diagnosed with high blood pressure.
You can lower your blood pressure by changing some aspects of your lifestyle and, if necessary, taking medication prescribed by a properly trained health care professional. Changing what you eat, how much you exercise and other ways you live your life can help you prevent or control high blood pressure. Here’s what you can do, along with suggestions for getting started.
Eat healthy food
Make sure your diet emphasizes fruits, vegetables, whole grains, and low-fat dairy foods. An easy tool for planning health meals is the Dietary Approaches to Stop Hypertension (DASH) diet which can help you reduce your systolic blood pressure by 8-14 mm Hg.
Get plenty of potassium, which can help prevent and control high blood pressure an pay attention to the amount of salt that's in the processed foods you eat, such as canned soups or frozen dinners.
Achieve and Maintain a Healthy Weight
If you're overweight, a modest reduction in weight of 10% of your current body weight can lower your blood pressure. For every kilogram of weight loss, you can reduce your blood pressure by 1.1/0.9 mm Hg.
Increase Physical Activity
Regular physical activity can help lower your blood pressure and keep your weight under control. Aiming for 30 to 60 minutes of physical activity four to seven days a week can decrease total blood pressure by 4.9/3.7 mm Hg.
Limit Your Alcohol Intake
Even if you're healthy, alcohol can raise your blood pressure. If you choose to drink alcohol, do so in moderation — one to two drinks per day for a weekly maximum of nine for women and 14 for men. Limiting your alcohol could decrease your systolic blood pressure by 2-4 mm Hg.
Smoking leads to injured blood vessel walls and speeds up the process of hardening of the arteries. If you smoke and want to quit, visit our section about Smoking.
Set aside some time every day to relax. Practice healthy coping techniques, such as muscle relaxation and deep breathing. Getting plenty of sleep can help, too.
Monitor Your Blood Pressure
Have your blood pressure checked regularly. High blood pressure often has no symptoms, so have yours checked by a health care professional at least once every two years or as often as your doctor suggests. If you have been told you have high-normal blood pressure, or pre-hypertension, Canadian guidelines recommend that you have your blood pressure checked at least once a year.
Home blood pressure monitoring is a good idea because it can help avoid the possibility masking your true blood pressure values. You can find home blood pressure monitors in drugstores, pharmacies, grocery stores, and department stores. If you are taking your blood pressure at home, here are some important things to consider to get the most accurate results.
- You may experience higher numbers when you are taking your blood pressure at the doctor’s office. This could be from the anxious feeling people sometimes get when a health care professional or someone in a white coat is present. This is known as white coat syndrome.
- This detailed video provides correct guidelines for measuring your blood pressure at home (Hypertension Canada).
- View a printable form for home measuring instructions.
About Lifestyle Changes
Doctors often first try to lower a patient’s blood pressure by having the patient make lifestyle changes, but like most change, it can be hard. If you had to focus on just three, the most important ones would be:
- Physical Activity: Get 30 to 60 minutes of exercise a day for as many as four to seven days a week
- Diet: Follow the DASH diet and aim for less than 2,300 mg sodium each day
- Quit Smoking: Find a program to help you quit
If your blood pressure is under control, you may be able to make fewer visits to your doctor if you monitor your blood pressure at home. If your doctor has prescribed medication, take it as directed.
But sometimes lifestyle changes are not enough. If blood pressure levels do not diminish after several months of lifestyle changes, or when very high blood pressure poses an immediate threat to health, medication may be necessary, particularly for those with organ damage, chronic kidney disease or diabetes.
Most people who are on blood pressure medication require at least two different drugs in addition to lifestyle changes to properly treat their condition.
To learn more about the many treatment options for lowering high blood pressure on our Hypertension Medication page. More detailed information about the diagnosis and treatment of high blood pressure is available from Hypertension Canada.