What is Blood Pressure, and Why Is It Important?

Blood pressure is the force your heart exerts on your artery walls when it pushes blood into the arteries with every heartbeat. Arteries are the blood vessels that carry oxygen- and nutrient-rich blood to every cell and tissue in your body. Blood pressure is, therefore, necessary for your whole body to function.

In contrast, veins are also blood vessels, but they carry blood from the body’s cells back to the heart. Blood pressure is a less important factor when blood reaches the veins because the oxygen has already been delivered. Therefore, when discussing blood pressure affecting blood vessels, we talk about arteries, not veins.

Both high blood pressure (hypertension) and low blood pressure (hypotension) can cause health issues. When blood pressure rises or drops, the body tries to offset it by speeding up or slowing down the heart rate and tightening or relaxing the blood vessels. Symptoms of hypotension (low blood pressure) or hypertension (high blood pressure) develop when the body cannot correct the fluctuations in blood pressure.

Blood pressure differs from heart rate, which is the number of times your heart beats per minute.

Factors Affecting Blood Pressure

Your blood pressure varies throughout the day. For example, it is lower when resting and higher when exercising. Other factors that can affect blood pressure include age, diet, health conditions, medications, and lifestyle factors like stress and alcohol use.

What is Normal, High, and Low Blood Pressure?

Blood pressure readings consist of two numbers measured in millimeters of mercury (mmHg). The upper number is the systolic pressure, which is the pressure in your arteries when your heart beats. The lower number is the diastolic pressure, which is the pressure in your arteries when your heart rests between heartbeats.

Normal Blood Pressure

Systolic blood pressure less than 120 mmHg and diastolic blood pressure less than 80 mmHg is considered normal blood pressure. Find out Which Is More Important: Systolic Or Diastolic Blood Pressure?

Low Blood Pressure (Hypotension)

Low blood pressure is defined as systolic blood pressure below 90 mmHg or diastolic blood pressure below 60 mmHg at rest. Normal blood pressure is defined as systolic blood pressure less than 120 mmHg and diastolic blood pressure less than 80 mmHg.

Stages of High Blood Pressure (Hypertension)

Elevated blood pressure:

Prehypertension: systolic 120-129 mmHg and diastolic less than 80 mmHg
Stage 1 hypertension: systolic 130-139 mmHg or diastolic 80-89 mmHg
Stage 2 hypertension: systolic 140 mmHg or higher or diastolic 90 mmHg or higher

Hypertensive crisis: systolic 180 mmHg or higher or diastolic 120 mmHg or higher; hypertensive crisis requires emergency medical treatment.

Common Symptoms of Low Blood Pressure

Many people with low blood pressure don’t have any symptoms. A slight decrease in blood pressure can occur with age and may not be evident. A more rapid drop in blood pressure can lead to reduced blood supply to many organs in the body, causing unpleasant and potentially dangerous symptoms.

Symptoms of low blood pressure may include:

Lightheadedness or dizziness
Syncope (fainting or passing out)
Fatigue, weakness, sluggishness, lack of energy
Nausea, vomiting, upset stomach
Blurred vision or faded vision
Fast and shallow breathing
Confusion
Trouble concentrating
Agitation or other unusual changes in mood and behavior

Additional signs that may make your healthcare provider suspect low blood pressure include:

A fast or slow heart rate
Pale skin color, especially in the fingers and toes
Cool kneecaps
Reduced urine output
Low cardiac output (the amount of blood pumped by your heart)

Risk Factors and Causes of Low Blood Pressure

Low Blood Volume

Low blood pressure occurs in people who are dehydrated due to a lack of enough fluids in their body. Dehydration reduces blood volume, causing the blood pressure to drop. Severe blood loss from injuries can also lead to decreased blood volume and low blood pressure.

Postural or Orthostatic Hypotension

Orthostatic hypotension means there is a large drop in blood pressure upon sitting or standing. It is measured when the blood pressure drops 20 mmHg or more (systolic) or 10 mmHg or more (diastolic), and remains low for over 3 minutes. Another name for this is postural hypotension because it occurs with changes in posture.

Orthostatic hypotension often occurs when you stand up too quickly. Gravity causes blood to pool in your lower extremities, and when you get up quickly, your body doesn’t have time to compensate and improve blood flow to your brain. Orthostatic hypotension causes low blood pressure and symptoms such as lightheadedness, dizziness, and fainting.

It is normal for your blood to drop briefly with a change in position, but it should not last long.

Postprandial Hypotension

Low blood pressure can occur after meals because blood is redirected to the digestive system to help digest food. This drop in blood pressure typically happens 1 to 2 hours after eating and is called postprandial hypotension. It's most common in adults over 65, especially those with underlying hypertension (high blood pressure), Parkinson's disease, and other conditions of the autonomic nervous system, which controls heart rate and breathing.

Neurally Mediated Hypotension

Neurally mediated hypotension is a drop in blood pressure that occurs after standing for a long time. It commonly affects young adults and children due to a miscommunication between the brain and the heart.

Heart and Lung Problems

Low blood pressure can develop if your heart beats too fast or too slow or you have heart valve disease. A weak heart muscle in people with advanced congestive heart failure can also result in low blood pressure. Another cause is that the lungs are not working properly.

Life-Threatening Health Conditions

Serious conditions such as a heart attack, cardiac arrhythmias (irregular heartbeat), pulmonary embolism (PE) (blood clot in the lung), a collapsed lung, anaphylaxis (severe allergic reaction), severe infection, and sepsis (severe immune reaction) can also cause low blood pressure.

Central Nervous System (CNS) Diseases

Conditions such as Parkinson’s disease can affect how your brain controls blood pressure.

Medication Side Effects

Certain medications can cause low blood pressure as a side effect. Examples include prescription medications used to treat high blood pressure, heart failure, depression, neurological problems, and erectile dysfunction. Certain over-the-counter herbal supplements and vitamins can also lower blood pressure.

Substance Use

Drinking alcohol or using illegal recreational drugs can cause unpredictable changes in blood pressure.

Pregnancy

Orthostatic hypotension can occur in the first and second trimesters of pregnancy. Internal bleeding and other complications during pregnancy or childbirth can also result in low blood pressure.

Temperature Variations

Blood pressure is generally lower in hot weather because the blood vessels relax (widen) as the body attempts to disperse heat. The opposite is true in cold weather and blood pressure tends to be higher. Extreme cold and hot temperatures can make hypotension worse.

Rare Conditions

Certain rare conditions, such as multiple system atrophy (Shy-Drager syndrome), can cause orthostatic hypotension and very high blood pressure when supine (lying down) due to problems with the autonomic nervous system.

Diagnosis and When to Seek Medical Help

How is Low Blood Pressure Diagnosed?

Low blood pressure (hypotension) is relatively easy to diagnose. However, determining its cause can be more challenging.

If you have low blood pressure, your healthcare provider may order a range of tests, including blood tests, imaging studies, ECG, EKG, tilt table tests, and others, to determine the cause.

When To See a Doctor for Low Blood Pressure?

If you notice low blood pressure on a home blood pressure measuring device, visit your healthcare provider. Getting evaluated by a medical professional is especially important if you have low blood pressure symptoms such as dizziness, fatigue, weakness, blurred vision, nausea, upset stomach, problems concentrating, confusion, or agitation.

You should also see your provider if you have repeated dizziness or fainting spells, even if you don’t have low blood pressure. These symptoms can be present in serious health conditions that should be diagnosed and treated.

When to go to the ER for Low Blood Pressure?

It can be dangerous if your blood pressure drops suddenly. A fall of just 20 mmHg can result in dizziness and fainting. More significant drops in blood pressure due to severe bleeding or serious allergic reactions can be fatal.

Seek emergency medical care for chest pain, passing out or fainting, or falls due to lightheadedness (especially if you take anticoagulant medications).

Complications of Untreated Low Blood Pressure

Low blood pressure can be a symptom of an underlying health condition, especially when there is a rapid drop in blood pressure alongside other associated symptoms. It’s important to find out the underlying cause of hypotension and treat it. If you don’t have low blood pressure treated, it can lead to:

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Managing Low Blood Pressure

Quick Home Remedies

It’s important to have low blood pressure evaluated by a healthcare professional before using home remedies to treat it. After you have talked to your provider for specific recommendations, you may be able to use these natural remedies to raise your blood pressure:

Dietary Modifications: Increase your fluid and salt intake to prevent symptoms of hypotension. Eat small, low-carbohydrate meals (rather than large meals) to prevent postprandial hypotension. Stay away from alcohol to lower your risk of low blood pressure due to dehydration. You should talk to your doctor first to make sure additional fluid and salt intake is safe for you, especially if you have kidney or liver disease and heart failure.
Lifestyle Changes: To prevent orthostatic hypotension, avoid standing up too quickly from a sitting or lying position to prevent orthostatic hypotension. Sit down if you feel dizzy or lightheaded. Falls due to low blood pressure can cause serious injuries.
Compression Socks: Wear compression stockings to apply gentle pressure on your lower legs and feet. Gentle pressure can help push more blood toward your heart and raise your blood pressure.

Medications and Treatments

Hypotension treatment depends on the underlying cause. It can range from IV fluids (intravenous or “into the veins” fluids) for low blood volume, antibiotics for serious infections, corticosteroids for a severe allergic reaction, or a heart transplant for heart failure.

Treatment of the underlying condition usually improves hypotension. For example, if you are dehydrated, replacing fluids can increase blood volume and raise your blood pressure. If you take medications that affect your blood pressure, your healthcare provider can change the dosage or switch you to a different medication.

Your doctors can also treat low blood pressure directly with medications:

Fluid resuscitation with intravenous (IV) fluids to increase blood volume.
Vasoconstrictor drugs to make your blood vessels narrower.
Medications that help your kidneys retain fluids and salt in your body to help with low blood pressure.

Frequently Asked Questions

What Happens When Your Blood Pressure is Low?

When your blood pressure is low, you may experience symptoms such as dizziness, weakness, lethargy, nausea, upset stomach, and trouble concentrating. A severe drop in blood pressure can result in reduced blood supply to the heart, brain, and other vital organs, which can be life-threatening and require immediate medical attention.

What is the Quickest Home Remedy for Low Blood Pressure?

Drinking more fluids, eating salty foods, and consuming caffeine can help to increase blood pressure quickly. You should only treat low blood pressure at home after you’ve been evaluated by a healthcare provider for underlying health conditions and potentially serious causes.

What is a Dangerously Low Blood Pressure Emergency?

A sudden drop in blood pressure can result in a life-threatening emergency called shock. Shock is the body’s reaction to reduced blood supply by shutting down organ systems. Signs and symptoms of shock for which you should seek emergency medical care include:

Cold and clammy skin
Pale skin color
A weak and rapid pulse
Rapid and shallow breathing
Confusion (especially in older adults)

Is 80/40 Blood Pressure Too Low?

Yes, a blood pressure reading of 80/40 is too low. This pressure means your systolic pressure is 80 mmHg, and your diastolic pressure is 40 mmHg. A resting blood pressure below 90/60 mmHg is called hypotension (low blood pressure) and should be evaluated by a healthcare professional.

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