When should i be worried about my diastolic blood pressure

Overview

What do your blood pressure numbers mean?

Blood pressure is a measure of the force of blood against the walls of your arteries. Blood pressure readings include two numbers. The first number is the systolic pressure (top number). This is the force of blood on the artery walls as your heart pumps. The second number is the diastolic pressure (bottom number). This is the force of blood on the artery walls between heartbeats.

If the top number stays high, or the bottom number stays high, or both, that means you have high blood pressure (hypertension). It's normal for blood pressure to go up and down throughout the day. Your doctor will give you a goal for your blood pressure.

What can cause blood pressure to go up or down?

It's normal for blood pressure to go up and down throughout the day. Things like exercise, stress, and sleeping can affect your blood pressure. Some medicines can cause your blood pressure to go up. These medicines include certain asthma medicines and cold remedies.

A low blood pressure reading can be caused by many things, including some medicines, a severe allergic reaction, or an infection. Another cause is dehydration, which is when your body loses too much fluid.

When should you call your doctor?

One high or low blood pressure reading by itself may not mean you need to call for help. If you take your blood pressure and it is out of the normal range, wait a few minutes and take it again. If it's still high or low, use the following guidance.

Call 911 anytime you think you may need emergency care. For example, call if:

  • You passed out (lost consciousness).

Call your doctor now or seek immediate medical care if:

  • Your blood pressure is much higher than normal (such as 180/120 or higher).
  • You think high blood pressure is causing symptoms such as:
    • Severe headache.
    • Blurry vision.
  • You are dizzy or lightheaded, or you feel like you may faint.

Watch closely for changes in your health, and be sure to contact your doctor if:

  • Your blood pressure measures higher than your doctor recommends at least 2 times. That means the top number is higher or the bottom number is higher, or both.
  • You think you may be having side effects from your blood pressure medicine.

Credits

Current as of: March 9, 2022

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine

Ask the doctor

When should i be worried about my diastolic blood pressure
Q. My doctor told me I should get a home monitor to keep tabs on my blood pressure. Which number is most important in the reading, the top or the bottom one?

A. This question comes up often, perhaps because doctors and patients alike tend to pay more attention to the top (first) number, known as systolic pressure. It reflects the amount of pressure inside the arteries as the heart contracts. The bottom (second) number, diastolic pressure, is always lower since it reflects the pressure inside the arteries during the resting phase between heartbeats.

As it turns out, both systolic and diastolic blood pressure are important. Per the most recent guidelines, you have what's called elevated blood pressure if your systolic blood pressure reading is 120 to 129 mm Hg (which stands for millimeters of mercury). Once your systolic reading reaches 130 or higher or your diastolic reading is 80 or higher, you're considered to have high blood pressure, or hypertension.

Most people have what's known as essential or primary hypertension, which means it's not caused by a medical condition, medication, or substance. Primary hypertension can affect both systolic and diastolic pressure to a similar degree. But sometimes, especially in older people, it affects mainly the systolic pressure; this is called isolated systolic hypertension.

Why does this happen? As you age, your arteries tend to become less elastic and less able to accommodate surges of blood. Blood flowing through your arteries at high pressure can damage the inner lining of these vessels, accelerating the buildup of cholesterol-laden plaque. This further stiffens and narrows the arteries, a condition known as atherosclerosis. Because the same volume of blood has to pass through a smaller area, the systolic pressure tends to rise, while the diastolic pressure remains the same or gradually falls over time. In some people with isolated systolic hypertension, the diastolic pressure reading may drop into the 50s or even the 40s.

Most studies show a greater risk of cardiovascular disease (especially strokes) related to high systolic pressure as opposed to elevated diastolic pressure. But in 2019, an eight-year-long study involving more than 1.3 million adults found that while elevated systolic pressure had a greater effect on cardiac outcomes, high diastolic readings also affected a person's risk, regardless of the systolic reading.

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.

— Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter

Image: © Vadim Zhakupov/Getty Images

What is an alarming diastolic number?

Once your systolic reading reaches 130 or higher or your diastolic reading is 80 or higher, you're considered to have high blood pressure, or hypertension.

What is an unhealthy diastolic number?

diastolic: 90 mm Hg or higher. High blood pressure (hypertension) systolic: 130 mm Hg or higher. diastolic: 80 mm Hg or higher. If you are diagnosed with high blood pressure, talk with your health care team about your blood pressure levels and how these levels affect your treatment plan.

When should I go to the ER for diastolic blood pressure?

Seek emergency care if your blood pressure reading is 180/120 or higher AND you have any of the following symptoms, which may be signs of organ damage: Chest pain. Shortness of breath. Numbness or weakness.

What factors affect diastolic blood pressure?

The factors discussed are heart rate, arterial pressure, coronary perfusion pressure, the pericardium, and the mechanical interplay between ventricles. The influence of heart rate, arterial pressure, and coronary perfusion pressure can be considered as minor provided they remain within their normal physiological range.