Blood pressure is the pressure that blood flow exerts on artery walls during the heart's beating cycle. Blood pressure that is too high or too low can cause symptoms like headaches.

High blood pressure (hypertension) is very common, affecting nearly half of adults in the United States, so much emphasis is placed on preventing and treating it. However, low blood pressure (hypotension) can also cause symptoms, and it can even be a side effect of hypertension treatment.

This article discusses signs of low blood pressure, including headaches, and ways to prevent low blood pressure.

Low Blood Pressure and Headaches

A normal blood pressure is considered less than 120/80 milligrams of mercury (mmHg). The top number is called the systolic reading and the bottom number is the diastolic reading. They correspond to the different parts of the heart's beating cycle.

Hypotension occurs when blood pressure is low and causes symptoms. This varies by individual. For example, someone whose resting blood pressure is typically high may experience symptoms of low blood pressure at a higher level than another individual.

While there is no specific cutoff for blood pressure to be called hypotension, a blood pressure below 90/60 mmHg in an otherwise healthy person may be considered low.

Headaches can have a range of causes. Low blood pressure is just one of many possibilities.

Signs and Symptoms of Low Blood Pressure

Low blood pressure can cause the following symptoms:

• Light-headedness or dizziness
• Fatigue or weakness
• Headache
• Confusion
• Nausea
• Visual changes
• Fainting
• Pale and clammy skin

Causes of Sudden Drops in Blood Pressure

A sudden drop of blood pressure is more likely to cause symptoms of hypotension, such as headache, fatigue, and dizziness. Sudden drops in blood pressure may be life-threatening, depending on the cause.

Orthostatic hypotension is a common cause of sudden blood pressure drop that occurs with standing. This can be caused or worsened by dehydration, certain medications (particularly those used to treat high blood pressure), problems with the nervous system (dysautonomia), and Parkinson's disease.

Other, more serious causes of a sudden blood pressure drop include the following:

• Bleeding, such as gastrointestinal bleeding, intra-abdominal bleeding, or bleeding from a traumatic wound
• Severe dehydration, such as from fluid losses in illnesses causing vomiting or diarrhea
• Certain medication overdose
• Anaphylaxis (potentially life-threatening allergic reaction)
• Sepsis (potentially life-threatening reaction to an infection)
• Arrhythmia (heart rate or rhythm problem) such as atrial fibrillation, ventricular tachycardia, and others
• Heart attack
• Pericardial tamponade (condition in which extra fluid fills the space around the heart)
• Pulmonary embolism (clot in a blood vessel)
• Fluid shifts during hemodialysis (procedure that uses a machine to filter and clean the blood)

Causes of Chronic Hypotension

While having high blood pressure is much more common than having low blood pressure, long-standing low blood pressure can also contribute to headaches and other symptoms.

Causes of chronic hypotension include the following:

• Dehydration
• Use of medications such as those that treat high blood pressure, heart failure, prostate enlargement, and erectile dysfunction
• Parkinson's disease
• Pregnancy
• Hypothyroidism (underactive thyroid)
• Adrenal insufficiency (Addison's disease)
• Liver disease
• Anorexia nervosa (abnormally low body weight)
• Nutritional deficiency, including of B12, folate, and iron
• Long COVID (when symptoms of COVID-19 persist for a long time after recovery)
• Postural orthostatic tachycardia syndrome (POTS)

Preventing Low Blood Pressure Headaches

If low blood pressure is found to be a cause of your headaches, there are some steps you can take to keep your blood pressure up.

Hydration

Ensuring that you are well-hydrated is one of the most important things you can do to combat hypotension.

While the amount of necessary fluid intake varies per person based on body weight, activity levels, and environment, one way to ensure you are drinking plenty of water is to pay attention to urine color. Pale yellow urine color is normal, whereas dark-colored urine is an indicator of dehydration.

Nutrition

You may have heard that eating a lot of salt can cause high blood pressure. In fact, the body needs salt to hold onto water. Those who have low blood pressure may benefit from increasing the amount of salt in their diet. Some people with orthostatic hypotension may be prescribed salt tablets for this reason.

Make sure that you are also getting adequate levels of vitamins and minerals, since deficiencies of vitamin B12, folic acid, and iron can contribute to hypotension.

Lifestyle

In addition to hydration and nutrition, some other lifestyle considerations can help prevent hypotension, particularly for those with postural hypotension:

• Participating in an exercise program or physical therapy
• Rising slowly from a lying or seated position
• Avoiding large meals (have smaller meals throughout the day instead)
• Using compression stockings or an abdominal binder
• Performing maneuvers such as tensing leg and abdominal muscles upon standing

Medications

Discuss medications with your healthcare provider to ensure that none of your current medications could be causing or worsening low blood pressure. There may be alternatives or dosing adjustments that can be prescribed.

In some cases, medications midodrine and fludrocortisone may be used to help increase blood pressure or help with symptoms of low blood pressure.

When to See a Healthcare Provider

A sudden drop in blood pressure that is accompanied by other symptoms should prompt you to seek medical care. Concerning symptoms include fainting, rapid heart rate, bleeding, chest pain, shortness of breath, and signs of dehydration, such as decreased urination.

Summary

Headaches can be caused both by very high blood pressure or low blood pressure. One of the most common causes of blood pressure drops accompanied by symptoms is orthostatic hypotension.

Preventing headaches from low blood pressure includes adequate hydration, proper nutrition, lifestyle considerations, and some medications.

A Word From Verywell

Headaches can be uncomfortable and painful, especially when accompanied by other symptoms. If you suspect low blood pressure is causing your headaches, contacting your healthcare provider can help you determine the cause and discover treatment options.