Given that people with high blood pressure (hypertension) are far more likely than others to die prematurely of heart disease and stroke, you might think that low blood pressure would be a good thing. However, abnormally low blood pressure, also called hypotension, can cause problems as well.
At the most basic level, hypotension can cause dizziness or blurry vision, which may increase the risk of falling or contribute to accidents. In more serious cases, it reduces the blood flow to the brain and other vital organs. This decreases the amount of oxygen and nutrients being delivered to these organs and impairs their ability to carry out normal functions. Hypotension may also indicate a more serious underlying health condition.
As blood travels throughout your body, it presses against the walls of your blood vessels, just like water in a hose or air in a tire. This is called blood pressure. When your heart beats (contracts), squeezing blood out and pumping it into your arteries, blood pressure peaks. This is called your systolic pressure. Between heartbeats, when your heart relaxes and blood flows back into it, your blood pressure is lower. This is your diastolic pressure.
A blood pressure reading measures these two pressures and expresses them as two numbers, your systolic pressure over your diastolic pressure. The normal blood pressure range for adults is lower than 120/80 mm Hg (mm Hg means "millimetres of mercury," referring to a pressure-measuring device similar to a thermometer).
Blood pressure changes throughout the day and varies from person to person. Various factors affect blood pressure, including your body position, breathing rhythm, stress level, physical activity, medications, what you eat or drink, and the time of the day (blood pressure is usually lowest at night when you sleep and rises when you wake up). In healthy individuals, your body responds and adapts to these changes to keep your blood pressure within a normal range. This ensures that vital organs, such as your brain and kidneys, receive a constant blood flow and nutrient supply.
When the systolic pressure drops below 90 mm Hg and the diastolic pressure falls below 60 mm Hg, this is categorized as low blood pressure. Some people may have low pressure all the time and this may be normal for them. If they do not experience any other signs or symptoms, medical treatment may not be necessary for them. Low blood pressure becomes a concern when it is accompanied by noticeable symptoms, such as dizziness, fainting and, in severe cases, shock. When this occurs, people should seek medical attention to determine if an underlying condition may be responsible for their hypotension.
Hypotension occurs when the body is unable to maintain blood pressure within a healthy range. Hypotension can be caused by a variety of factors and can affect people of all ages. However, there are certain types of hypotension that are more likely to affect certain age groups than others.
Orthostatic hypotension occurs when there is a sudden drop in blood pressure when a person stands up from a sitting or lying down position. This more commonly affects older adults.
Neurally mediated hypotension (NMH) results when a person has been standing for a long period of time or after having an unpleasant or upsetting experience. This is commonly referred to as fainting. Young children are more likely than adults to experience this form of hypotension, and will often outgrow NMH or a tendency to faint easily.
Low blood pressure can occur for some people after eating. This is called postprandial hypotension.
Other factors may cause low blood pressure:
In certain instances, people may experience low blood pressure but otherwise feel fine. Hypotension becomes a concern when it is accompanied by one or more of the following symptoms:
In the case of shock, a person may at first experience any of the above signs or symptoms. Over time, without immediate medical attention, a person may become unconscious.
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