Your blood pressure is the force inside your blood vessels when your heart beats and relaxes. This force is measured in millimeters of mercury (mm Hg) and is represented as two numbers.

The upper number, called your systolic pressure, is measured when your heart beats. The lower number, called your diastolic pressure, is measured when your heart relaxes between beats.

High blood pressure can increase your risk of heart disease or stroke, but low blood pressure can also be a problem.

The medical term for low blood pressure is hypotension. If you have hypotension, your systolic pressure measurement is under 90 mm Hg and your diastolic number is under 60 mm Hg. Doctors have started to raise concerns specifically about diastolic blood pressure below 60.

Some people can have low diastolic pressure even when their systolic pressure is typical. This condition is called isolated diastolic hypotension. Low diastolic blood pressure may be particularly dangerous for your heart.

Unlike the rest of your body, which receives blood when your heart pumps, the muscles of your heart receive blood when your heart relaxes.

If your diastolic blood pressure is too low, your heart muscles won’t get enough oxygenated blood. This can lead to weakening of your heart, a condition called diastolic heart failure.

You may be at higher risk of this type of heart failure if you have coronary heart disease, which is narrowing of your heart arteries.

Symptoms of isolated diastolic hypotension include tiredness, dizziness, and falls.

Because low diastolic pressure decreases blood flow to your heart, you may also have chest pain (angina) or symptoms of heart failure, including:

  • shortness of breath
  • swelling of your feet or ankles
  • confusion
  • heart palpitations
Medical emergency

Call 911 and go to the nearest emergency room if you have chest pain or difficulty breathing.

Symptoms of low diastolic blood pressure and low systolic blood pressure

Symptoms of low diastolic blood pressure along with low systolic blood pressure (hypotension) include:

  • dizziness
  • fainting (syncope)
  • frequent falls
  • tiredness
  • nausea
  • blurred vision

Seek medical attention if you have any of these symptoms.

Causes of diastolic hypotension by itself

There are three known causes of isolated diastolic hypotension:

Medications

  • Alpha-blocker medications. These blood pressure medications work by causing your blood vessels to open up (dilate). Because they lower diastolic pressure more than systolic pressure, they may cause isolated diastolic hypotension. Common brand names include Minipress and Cardura.

Lifestyle

  • Aging. As we age, we lose the elasticity of our arteries. For some older adults, arteries may become too stiff to spring back between heartbeats, causing diastolic blood pressure to be low.
  • Too much salt in your diet. Dietary salt can decrease elasticity of your blood vessels. If you take in too much salt, you may increase your risk of low diastolic blood pressure.

Causes of overall low blood pressure

There are several common causes of overall hypotension, which would include a low diastolic number.

Medications

Medical conditions

  • Heart problems. Heart valve problems, heart failure, and a very slow heart rate (bradycardia) can lead to hypotension.
  • Dehydration. If you don’t take in enough fluids, your blood pressure can fall dangerously low. This may happen if you’re taking a diuretic and lose more fluids than you take in.

Treatment for low diastolic blood pressure largely depends on the type of hypotension. Your doctor will assess this closely to determine the appropriate treatment plan.

Isolated diastolic hypotension

Treating isolated diastolic hypotension is more difficult than treating general hypotension. If you’re taking an alpha-blocker, your doctor can prescribe a different high blood pressure medication.

If you have isolated low diastolic pressure and you’re not on blood pressure medication, the only option may be to see your doctor more frequently for checkups and to watch for symptoms of heart failure.

Currently, there’s not any medication available to treat isolated diastolic hypotension.

General hypotension

Treatment of general hypotension depends on the cause.

Overtreatment of high blood pressure can be managed by adjusting or changing medications. The goal is to keep the diastolic blood pressure between 60 and 90 mm Hg. Your doctor may also change other medications that cause hypotension.

Dehydration can be treated with fluid replacement. In some cases, you may need medications that increase blood pressure.

Low diastolic blood pressure doesn’t always lead to a larger health problem. But in some cases, the effects of low diastolic blood pressure can be long lasting and potentially life threatening if left untreated.

Complications of low diastolic blood pressure include:

Risk of injury from falls

If your blood pressure is low enough, the drop can cause symptoms such as fainting or dizziness.

This causes a significant risk of falling since you’re not conscious to stop the fall. Additionally, you’re not aware of how badly you’ve injured yourself during a fainting spell. This can lead to serious injuries, such as head trauma from hitting your head.

Heart tissue damage and heart disease

Researchers have found a link between low diastolic blood pressure and heart damage.

A 2016 study that lasted more than 3 decades and involved more than 11,000 people found that a diastolic blood pressure below 60 mm Hg is dangerous.

People with this level are 50 percent more likely to have heart damage. This is compared with those who have a low diastolic pressure level between 80 and 89 mm Hg.

Heart disease is another concern. The same study found that those with low diastolic blood pressure were 49 percent more likely to develop heart disease.

There are some things you can do to help prevent and manage low diastolic pressure:

  • Try to keep your salt intake to between 1.5 and 4 grams per day. An ideal number is about 3.5 grams. Read food labels to avoid added salt in your diet.
  • Eat a heart-healthy diet. This diet includes plenty of fruits, vegetables, and whole grains. For protein, stick to lean meats and fish. Avoid fatty foods.
  • Drink enough fluids and avoid alcohol, which can increase your risk of dehydration.
  • Stay physically active and start an exercise program. Ask your doctor what type and amount of exercise is safe for you.
  • Maintain a moderate weight. If you’re overweight, your doctor can help you create a safe weight loss plan.
  • If you smoke, quit. Quitting can be difficult, so consider reaching out for support.

Hypotension can be dangerous because it’s a frequent cause of falls. Isolated diastolic hypotension can be especially dangerous because it can decrease blood flow to your heart.

You may be at higher risk of low blood pressure if you have coronary artery disease. Over time, isolated diastolic hypotension can cause heart failure. In fact, it may be one of the most common causes of heart failure.

Pay attention to your diastolic number when you have your blood pressure checked. If your lower number is 60 or below, ask a healthcare professional about it.

Let a doctor know if you have any symptoms of hypotension or heart failure. In many cases, switching medications along with making lifestyle changes can help. A doctor may want to follow you more closely to ensure your diastolic pressure stays above 60.