How is blood pressure measured, and what constitutes hypotension?

Key takeaways

1. Low blood pressure (hypotension) occurs when blood pressure falls below levels needed for stable circulation, and symptoms, not just the numbers, determine whether it requires treatment.
2. Common symptoms include dizziness, fainting, blurred vision, fatigue, difficulty concentrating, nausea, and worsening symptoms when standing or after heat exposure.
3. Causes may include dehydration, medications, endocrine conditions, heart rhythm problems, prolonged bed rest, or nutritional deficiencies. Identifying the underlying cause is an integral part of management.
4. Treatment may involve hydration, controlled salt intake under medical guidance, compression garments, exercise, medication, and addressing any underlying condition contributing to low blood pressure.
5. Medical assessment is advised if symptoms persist or worsen, or if they include fainting, chest discomfort, palpitations, or cognitive changes. HeartWest can assess and manage heart-related causes of hypotension.
Low blood pressure, or hypotension, occurs when circulation is lower than the body needs. Although high blood pressure is more commonly discussed, low blood pressure can also affect daily well-being and organ function.

Readings below 90/60 mmHg may cause symptoms in some people, while others—especially younger or very fit individuals—have naturally low readings without concern. What matters is whether the level is low for that person and whether symptoms are present.

Let’s discuss sodium’s role, how blood pressure is measured, the causes and symptoms of hypotension, how high sodium levels affect circulation, the tests used for diagnosis, treatment options, and when to seek medical review.

How blood pressure is measured

Blood pressure is recorded using two numbers:

Systolic pressure: The pressure in the arteries when the heart contracts.

Diastolic pressure: The pressure in the arteries when the heart relaxes.

A typical reading is recorded as:
Systolic / Diastolic (e.g., 120/80 mmHg)

Hypotension is generally considered:

Systolic below 90 mmHg, or
Diastolic below 60 mmHg

However, diagnosis is based on both readings and symptoms.

Why does low blood pressure occur?

Low blood pressure can arise from several factors, often occurring together. It may result from reduced blood volume, medication side effects, or changes in how the heart or endocrine system regulates circulation. Typical causes include:

Inadequate fluid intake or dehydration
Medications such as blood pressure tablets, diuretics, or antidepressants
Heart rhythm issues, endocrine disorders, nutritional deficiencies, or pregnancy

Understanding the cause helps guide the most suitable treatment.

Symptoms of low blood pressure

Some people feel well despite low readings, while others develop symptoms when circulation cannot meet the body’s demands. These symptoms may appear gradually or during particular situations. Common signs include:

Dizziness, blurred vision, fainting, or nausea
Fatigue, weakness, or difficulty concentrating
Cold or clammy skin, with rapid, shallow breathing—especially after standing quickly or being in the heat

If symptoms persist or interfere with daily activities, a medical review is recommended.

Potential complications of hypotension

If blood pressure stays too low for an extended period, it can reduce blood flow to vital organs. This may lead to more serious effects beyond everyday symptoms. Key concerns include:

A higher risk of falls or fainting episodes when blood flow to the brain drops
Reduced circulation to the heart or kidneys, affecting how these organs function over time
Pregnancy-related complications occur if blood flow to the placenta is affected

Sudden, severe, or worsening symptoms should be assessed promptly.

Why sodium matters when blood pressure is low

Sodium supports several essential processes that keep the body functioning well. It helps regulate fluid balance, nerve signals, and muscle contractions. When blood sodium levels change, you may notice the effects on:

Overall fluid levels in the body, which can raise or lower blood pressure
How the heart and blood vessels respond to changes in circulation
Symptoms of hypotension, especially when sodium levels fall and blood pressure drops

This relationship helps explain why sodium intake influences blood pressure and well-being.

Diagnosis and management of low blood pressure

Identifying the underlying cause of low blood pressure is an important step in choosing the appropriate treatment. Your doctor may look at how your readings change throughout the day or in different positions, and may review results from Home monitoring or a 24-hour BP monitoring test.

Assessment often includes:

Blood pressure checks while resting, during activity, or across a full day
Blood tests to check for anaemia, electrolyte imbalance, kidney function, or thyroid conditions
An ECG or a tilt table test to review the heart rhythm or how blood pressure responds to position changes

Management aims to improve circulation and ease symptoms. Many people improve with simple changes, while others may need more tailored support. Helpful steps include:

Drinking enough fluids and adjusting salt intake when advised
Avoiding triggers such as heat, long periods of standing, or sudden posture changes
Supporting circulation with regular physical activity or compression garments

Symptoms often improve once underlying issues such as dehydration, anaemia, thyroid imbalance, medication effects, or heart rhythm concerns are addressed.

Where can I go for a low blood pressure assessment?

HeartWest provides care for adults experiencing low blood pressure or other cardiovascular concerns across five locations in Melbourne’s western and north-western regions. The team can assist with:

General cardiology, heart failure, and cardiac imaging needs
Interventional cardiology procedures, electrophysiology, and pacing concerns
Cardiothoracic assessments and ongoing follow-up care

If you are experiencing symptoms of low blood pressure or have concerns about your readings, you can arrange an appointment for further assessment. Contact us for more information or to request an appointment.

FAQs

1. What symptoms indicate low blood pressure?

Symptoms of hypotension may include dizziness, fainting, blurred vision, fatigue, nausea, headaches, and difficulty concentrating. Some people also experience a rapid heartbeat or worsening symptoms when standing. If these symptoms occur regularly, a medical review is recommended.

2. What causes low blood pressure?

Low blood pressure can be caused by dehydration, medication side effects, heart rhythm problems, hormonal or endocrine conditions, prolonged bed rest, nutritional deficiencies, anaemia, or neurological conditions affecting blood pressure control. Identifying the cause helps guide treatment.

3. How is low blood pressure diagnosed?

Diagnosis may include blood pressure monitoring, orthostatic readings, blood tests, ECG, and, in some cases, a tilt table test. These assessments help determine whether symptoms are related to blood pressure changes or another condition.

4. How can low blood pressure be managed?

Management depends on the cause and symptoms. It may include increasing fluid intake, adjusting salt intake under medical guidance, wearing compression stockings, modifying medications, exercising regularly, and addressing underlying conditions such as hormonal imbalance or anaemia.

5. When should I seek medical care for low blood pressure?

You should seek medical care if you have frequent dizziness, fainting, persistent fatigue, chest discomfort, palpitations, or confusion. Immediate assessment is recommended if symptoms develop suddenly or worsen quickly, or if they interfere with daily activities.