Causes of High Blood Pressure

Medically Reviewed by Poonam Sachdev on December 18, 2023
8 min read

Blood pressure is the measure of the force of blood pushing against blood vessel walls. The heart pumps blood into blood vessels, which carry the blood throughout the body.

High blood pressure, also called hypertension, means your heart is working harder to pump blood out to the body. It's a dangerous condition and contributes to hardening of the arteries, or atherosclerosis, stroke, kidney disease, and heart failure.

High blood pressure, or hypertension, affects nearly half of adults in the U.S. Because it usually doesn’t make you feel sick, many people are surprised to hear that they have it.

However, high blood pressure can have a big impact on your health, so it is important to understand what it is, what causes it, and how you can lower it.

A blood pressure reading is written like this: 120/80. It's read as “120 over 80.” It is measured in mmHg, which is a unit that doctors use to describe pressure. This is like how you use inches to describe length.

The top number of the reading is called the systolic pressure, and the bottom number is called the diastolic pressure. The systolic number measures your blood pressure at the exact moment your heart beats. Meanwhile, the diastolic number measures your blood pressure between each heartbeat.

The ranges are:

  • Normal: Less than 120 mmHg/less than 80 mmHg
  • Elevated: 120-129 mmHg/less than 80 mmHg
  • Stage 1 hypertension: 130-139 mmHg/80-89 mmHg
  • Stage 2 hypertension: 140 mmHg or higher/90 mmHg or higher
  • Hypertensive crisis: 180 mmHg or higher/120 mmHg or higher -- See a doctor right away

If even one of the numbers is in the hypertension range, you have it. For example, someone with a blood pressure of 133/79 has stage 1 hypertension.

If your blood pressure is above the normal range, talk to your doctor about how to lower it. Call 911 if you're having a hypertensive crisis.

Your blood pressure depends on how much blood your heart pumps and how difficult it is for your blood to flow through your arteries. Things that affect either of these factors, such as being dehydrated or having narrow arteries, can impact your blood pressure.

Several things may play a role in causing high blood pressure. Depending on what is causing your high blood pressure, your doctor will determine which type of hypertension you have: primary (or essential) or secondary. You can have one or both types.

Essential hypertension

When there isn’t an obvious cause of high blood pressure, it is called primary (or essential) hypertension. In the U.S., 19 out of 20 people with high blood pressure have this type of hypertension. It often takes many years to develop.

Essential hypertension has been linked to certain risk factors in your diet and lifestyle. For example, eating a lot of salt can cause your blood pressure to rise. Many people with this condition are sensitive to salt, so even eating a small amount can trigger a spike in blood pressure. 

Other risk factors that can raise the risk of having essential hypertension include:

  • Not getting enough exercise
  • Drinking too much alcohol
  • Having a family member with high blood pressure
  • Getting older (especially after 65 years of age)
  • Obesity
  • Diabetes
  • Stress
  • Insufficient intake of potassium, calcium, and magnesium
  • Lack of physical activity
  • Chronic alcohol consumption

Secondary hypertension

When a direct cause for high blood pressure can be identified, the condition is described as secondary hypertension. This type of high blood pressure is caused by a different health condition. It is usually more sudden and severe than essential hypertension. Some causes include:

  • Kidney disease. This is the most common cause of secondary hypertension.
  • Adrenal disorders. Hypertension can also be triggered by tumors or other abnormalities of adrenal glands (small structures that sit atop the kidneys). Adrenal tumors or disorders can cause them to release too much of the hormones that elevate blood pressure.
  • Thyroid disorders. Too much or too little thyroid hormone can affect your blood pressure.
  • Congenital heart defects. Some people are born with heart or blood vessel problems.
  • Obstructive sleep apnea. This condition causes breathing problems and lack of oxygen. This can harm your arteries.
  • Birth control pills. Pills used for birth control (specifically those containing estrogen) and pregnancy can boost blood pressure.
  • Cough, cold, and pain-relieving medications. These can temporarily raise blood pressure.
  • Certain medications. Some drugs can constrict blood vessels, making it harder for the heart to pump blood. 
  • Illegal drugs. Cocaine and amphetamines can raise blood pressure.


Sometimes, hypertension suddenly appears or gets worse during pregnancy. When hypertension develops after 20 weeks of pregnancy, it is called preeclampsia.

It is important to keep an eye on your blood pressure because it can have a big impact on you and your baby. Both high blood pressure and preeclampsia can cause problems such as:

  • Slow growth
  • Low birth weight
  • Prematurity
  • Separation of the placenta before delivery
  • Organ damage

Talk with your doctor about how to best monitor your blood pressure during pregnancy. Watch out for symptoms including headaches, vision problems, stomachache, nausea, and shortness of breath. These are signs of preeclampsia. Your doctor also can test for other signs of preeclampsia, such as having too much protein in your pee.

If you have high blood pressure or preeclampsia during pregnancy, it is very important to treat it. Your doctor can prescribe blood pressure medications that are safe for pregnant people. They also might recommend lifestyle changes such as regular activity and a healthy diet.

Causes of sudden high blood pressure

It is normal for your blood pressure to go up and down throughout the day. Many things can temporarily raise blood pressure. For example, your blood pressure might rise after a stressful event, smoking, or drinking alcohol.

But when your blood pressure rises too much, it can be a medical emergency. This is called a hypertensive crisis. It happens when your blood pressure is higher than 180 mmHg/higher than 120 mmHg. It can cause symptoms such as:

  • Difficulty breathing
  • Racing heartbeat
  • Chest pain
  • Anxiety
  • Headache
  • Dizziness
  • Nausea
  • Trouble speaking
  • Vision problems
  • Nosebleed

If you think you are having a hypertensive crisis, call 911 right away.

There are several risk factors for high blood pressure, including:

  • Smoking. When you smoke, vape, or chew tobacco, your blood pressure temporarily increases. Over time, regular smoking can damage and harden your blood vessels.
  • Being overweight or obese. Extra weight impacts your heart and blood vessels. For example, it can cause high cholesterol.
  • Lack of physical activity. People who don’t exercise tend to have higher heart rates.
  • Eating too much salt. Salt causes your body to hold onto water. This increases the amount of blood being pushed through your arteries.
  • Not eating enough potassium. Potassium helps balance the amount of salt and water in your body. Dehydration also can affect your potassium levels.
  • Drinking too much alcohol. Having more than one to two drinks per day can increase your blood pressure, especially if you are a man.
  • Stress. Feeling nervous or stressed can temporarily raise your blood pressure. When this happens at the doctor’s office, it is called white coat syndrome.
  • Age. As you get older, you are more likely to get high blood pressure. High blood pressure usually affects adults, but it is becoming more common among kids. 
  • Sex. Among people under age 64, high blood pressure is more likely to affect men than women. But after age 65, women are at a higher risk.
  • Family history. High blood pressure tends to run in families. 
  • Race. In the U.S., high blood pressure is more common among Black people than white people. It also usually starts at an earlier age. Blood pressure control, among those for whom blood pressure medication is recommended, is lower among Asian people and Black people compared to non-Hispanic white people.
  • Pregnancy. Blood pressure can rise during pregnancy. 
  • Certain health conditions. People with chronic kidney disease, adrenal and thyroid disorders, and sleep apnea are at risk for secondary hypertension.
  • Certain medications. Birth control pills, anti-inflammatory drugs, and other medicines can cause your blood pressure to go up.

There are many different causes of high blood pressure. Some risk factors, such as your age and family history, are things that you cannot change. However, many healthy habits, including eating a low-salt diet and getting regular exercise, can help lower your blood pressure. Talk with your doctor about how to manage your blood pressure and whether medication might help.

How do you feel when your blood pressure is high? High blood pressure usually doesn’t cause any obvious symptoms. Many people with high blood pressure feel fine, so they might not even realize they have it. However, if your blood pressure is very high (180 mmHg or above/120 mmHg or above), you might have heart palpitations, chest pain, dizziness, headaches, or other symptoms. These are signs of a hypertensive crisis, which is a medical emergency. If you think you are having a hypertensive crisis, call 911 immediately.

How do I lower my high blood pressure? 

There are many healthy habits that can help lower your blood pressure. You can try:

  • Eating a healthy, low-salt diet
  • Getting plenty of exercise
  • Quitting smoking
  • Avoiding alcoholic drinks
  • Losing weight (if you are not at a healthy weight)

Some people might also need medication to control their blood pressure. Ask your doctor if medication might be right for you.

What is stroke-level blood pressure? High blood pressure is the biggest risk factor for strokes. In general, to lower your risk for stroke, try to keep your blood pressure under control. A hypertensive crisis (blood pressure of 180/120 mmHg or higher) can cause an immediate stroke.

What is the normal blood pressure level by age? As you get older, your blood pressure tends to get higher. This is because arteries tend to become stiff and collect plaque over time. If you are over 50 years old, it is especially important to pay attention to your blood pressure. The ranges for healthy and unhealthy blood pressure are the same for all adult age groups.