These two numbers are called the systolic blood pressure and the diastolic blood pressure. They are measured by using a cuff with an attached gauge so that the numbers can be read by a machine, or by a person hearing the pressure rise and fall through a stethoscope. Both numbers are important but not always for the same reasons.
This article looks at how blood pressure is taken, what levels are normal, and what some of the results can mean. When the heart beats, blood pulses through the arteries to travel throughout the body. It is not the steady stream you might see from a garden hose or water faucet. The pulse of the the blood flow and the pressure it exerts change from moment to moment. It's highest during the heartbeat this is the systolic pressure and lowest between beats diastolic. A blood pressure reading includes both these measurements.
Doctors measure blood pressure in these numbers so that there is a standard way of describing the force of the pulsing blood. Both the systolic and diastolic pressures are important. If the readings are too high, it may mean a person has high blood pressure.
If the readings are too low, there may not be enough blood flowing to the brain and other critical organs. If there are changes in the difference between the two numbers, it's a clue that there may be a heart condition or other problem. During a heartbeat, the heart is pushing blood out into the arteries. Doctors call this "systole," and that's why it's called the systolic blood pressure. It's the pressure during a heartbeat and the highest pressure measured.
When the reading is mmHg or a little below while a person is sitting quietly at rest, the systolic blood pressure is considered normal. The heart muscle pushes out blood with higher pressure when a person is exercising , under stress, or at similar times when the heart rate is increased.
The systolic pressure goes up with it. In these cases, the increased pressure is normal. However, when the pressure is high while a person is resting, that's considered high blood pressure.
That's why it is so important to take your blood pressure during periods of quiet rest to diagnose hypertension , or high blood pressure. High systolic blood pressure is usually caused by narrowing of the arteries, which makes the heart have to work harder to push blood through. If the systolic blood pressure is lower than normal, it's called hypotension.
If this low blood pressure is serious enough, it can cause lightheadedness , dizziness , or fainting. If it lasts long enough and it isn't treated, it may cause organs like your kidneys to start shutting down. Systolic hypotension can occur if the amount of blood in your body becomes too low. This can happen if you are severely dehydrated or you have major bleeding; there just isn't enough blood to push through the body.
It also may happen if the heart muscle is too weak to push blood normally, as in cases of cardiomyopathy damaged heart muscle or if the arteries suddenly widen too much, as in vasovagal syncope a reflex that causes fainting. ISH can be treated like other forms of hypertension.
The goal is to reduce your systolic blood pressure to below mm Hg. This can be accomplished through implementation of lifestyle changes, through medication, or both.
Lower-than-normal diastolic blood pressure may lead to heart damage. A review of studies in elderly adults with ISH has found that the following medications had the greatest efficacy in reducing risk of stroke and other cardiovascular events.
The following drugs were found to have less efficacy, however they may still be effective in treating ISH. You may also need to make some lifestyle changes as part of your ISH treatment plan. These can include:. You can help to prevent high blood pressure by practicing all of the lifestyle changes mentioned above. Additionally, you should work with your doctor to carefully manage any preexisting health conditions that can contribute to high blood pressure, such as diabetes. The symptoms of high blood pressure are typically silent.
Many people may not find out they have high blood pressure until they visit their doctor for a routine physical. There are many home blood pressure monitors available so that you can monitor your blood pressure at home. Some people that should consider doing this include:. You should always keep a log of your readings. If you find that your readings are consistently high, you should make an appointment with your doctor to discuss them.
Isolated systolic hypertension is when your systolic blood pressure is high, but your diastolic blood pressure is normal. It can occur naturally with age or can be caused by a variety of health conditions including anemia and diabetes. ISH should still be treated even though your diastolic pressure is normal. This is because untreated high blood pressure, including ISH, can lead to a risk of things like heart attack and stroke. Be sure to have regular physical checkups with your doctor during which your blood pressure is taken.
If you have high blood pressure, your doctor will work with you to develop a plan to manage it. If your low blood pressure is caused by an infection, your doctor might prescribe an antibiotic to treat the infection. Proper management of the problem can help improve or limit episodes of low blood pressure. Unmanaged high blood pressure can lead to:. Symptoms or complications that may occur from low blood pressure can include:. You may head off blood pressure problems before they start, or limit your risk, if you follow a healthy lifestyle.
In addition, if you suspect you have sleep apnea symptoms, such as heavy snoring, daytime sleepiness, or restless sleep, talk to your doctor about a sleep study. Sleep apnea is believed to affect at least 25 million American adults. Research has shown that using a CPAP machine while sleeping can reduce blood pressure in people with sleep apnea.
To help prevent low blood pressure, drink plenty of fluids, preferably water, to prevent dehydration. Stand up slowly from a sitting position to help prevent orthostatic hypotension. Also, notify your doctor right away if you feel a medication is causing your blood pressure to drop.
There may be another medication option that will have less impact on your blood pressure numbers. Discuss which symptoms you should look out for and how to best monitor your condition. For many people, high or low blood pressure is manageable.
Shop for a home blood pressure monitor. High blood pressure readings are different for adults, children, and pregnant women. Learn which levels constitute high blood pressure for these…. High blood pressure is often associated with few or no symptoms. Many people have it for years without knowing it. Learn more.
Foods that are rich in potassium, magnesium, and calcium can help lower blood pressure. To ensure accurate readings when you're checking your blood pressure at home, be sure to sit comfortably with your back supported, your feet flat on the floor, and your arm resting on a table with your palm facing up.
If needed, support your arm with a pillow so that your elbow is at the level of your heart. As a service to our readers, Harvard Health Publishing provides access to our library of archived content.
Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
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