Cardiovascular disease
Low blood pressure (hypotension)
Low blood pressure, also known as hypotension, means the pressure inside your blood vessels is lower than it needs to be. Blood pressure below 90/60mmHg is classed as hypotension, and they can cause symptoms such as dizziness and fatigue. When blood is not being pumped with enough pressure to meet the body's needs, it can lead to fainting or blackouts, otherwise known as syncope.
What low blood pressure is
Blood pressure is a measurement of the pressure at which blood flows through your blood vessels. Two numbers are recorded during a blood pressure measurement, a systolic and a diastolic reading, and both are recorded in millimetres of mercury (mmHg).
The systolic reading is the force with which your heart pumps blood under pressure, during systole. The diastolic reading is measured when the heart is at rest and reflects the resistance of the blood flow in the vessels between heartbeats. The British Heart Foundation puts the normal range at 90/60mmHg to 130/85mmHg.
Readings below 90/60mmHg are known as hypotension, or low blood pressure. It sits at the opposite end of the scale to hypertension, where readings of 140/90mmHg or higher are classed as high blood pressure.
- Systolic pressure is the top number, the force with which the heart pumps blood out
- Diastolic pressure is the bottom number, the resistance in the vessels between beats
- A reading below 90/60mmHg is classed as hypotension
- A reading of 140/90mmHg or higher is classed as hypertension
What happens in the heart and circulation
With hypotension, blood is not being pumped with enough pressure to meet the body's needs. Blood flow to the brain can then fall below what it needs, and that is what produces the symptoms.
The brain depends on a continuous supply of oxygen-rich blood. If that supply drops, even for a short time, the body responds by briefly shutting down. This is what happens during a faint, or syncope.
A drop in blood pressure can happen for many reasons. It may occur when you stand up quickly, or as a result of dehydration, medication, or certain medical conditions. In some cases the heart itself does not respond quickly enough to maintain stable circulation.
Where the heart is involved, the causes tend to fall into three broad groups. A slow heart rhythm may not pump enough blood to meet the body's needs. A fast or irregular rhythm may not allow the heart to fill and pump effectively. Conditions affecting the heart muscle or valves can reduce the efficiency of blood flow, particularly when demand rises during physical activity.
Symptoms you may notice
Low blood pressure can cause symptoms such as dizziness and fatigue. The dizziness tends to be described as light-headedness, or a feeling of nearly fainting, rather than the spinning sensation of vertigo, which is usually related to the inner ear rather than the heart.
If the pressure falls far enough, it can lead to fainting or blackouts. Most episodes last only a few seconds to a minute, and people often recover quickly, although they may feel tired or unsettled afterwards.
Many people describe warning symptoms such as light-headedness, nausea or blurred vision before they lose consciousness. In some cases, however, fainting happens with no warning at all.
- Dizziness
- Light-headedness, or a feeling of nearly fainting
- Fatigue
- Fainting or blackouts, known as syncope
- Nausea before an episode
- Blurred vision before an episode
When low blood pressure may be linked to the heart
Not every drop in blood pressure points to a heart problem. One of the most frequent causes of fainting is vasovagal syncope, where the body overreacts to triggers such as pain, emotional stress, or standing for long periods, which leads to a temporary drop in heart rate and blood pressure. Dehydration, sudden changes in posture, low blood sugar and heat exposure are also common causes and are generally benign.
Certain patterns do make a cardiac cause more likely, and Dr Jogiya will pay closer attention when symptoms fall into these groups.
A common mistake is to dismiss these episodes, particularly when they are brief. What tends to happen is that patients wait until the episodes become more frequent before seeking advice. Early assessment is always preferable.
- Dizziness or fainting that occurs during physical activity
- Fainting that happens suddenly, with no warning symptoms
- Symptoms that occur alongside palpitations
- Symptoms that occur alongside chest discomfort or breathlessness
- Episodes in someone already known to have heart disease
- Fainting that happens more than once, or that results in injury
How low blood pressure is diagnosed
Assessment usually begins with a detailed discussion of your symptoms. Dr Jogiya will usually ask when the dizziness or faintness occurs, how long it lasts, and whether it is linked to activity or to a change of posture.
Blood pressure is then measured directly, including lying and standing readings.
Tests of the heart itself are used to look for a rhythm or structural cause.
Symptoms often come and go, which can make diagnosis more difficult. Capturing the heart rhythm during an episode is frequently what provides the answer.
- A 12 lead ECG to assess the heart rhythm
- An ECG monitor worn over a longer period to detect intermittent rhythm problems
- An echocardiogram to assess the structure and function of the heart
- Blood pressure monitoring, including lying and standing readings
What you can do day to day
Some simple measures can reduce how often symptoms occur, particularly where low blood pressure is related to posture, hydration or lifestyle.
If you feel light-headed or sense that you may faint, sit or lie down immediately. These measures can help, but they should not replace medical assessment when episodes are recurrent or unexplained. Where an underlying rhythm problem or structural heart problem is identified, treatment is directed at that condition.
- Stay well hydrated
- Rise slowly from sitting or lying positions rather than standing up quickly
- Avoid standing still for prolonged periods
- Maintain regular meals
- Prioritise sleep and manage stress
- Keep a note of when symptoms occur and what you were doing at the time
When to seek help
Call 999 immediately if someone collapses and does not wake up quickly, or if a faint or a blackout comes with chest pain, or with signs of a stroke, or leaves someone injured. A stroke needs immediate and urgent treatment.
Arrange an assessment promptly if fainting happens more than once, happens during exercise, occurs without any warning, or comes alongside chest discomfort or palpitations. Fainting during exertion is always taken seriously and should always be investigated promptly. Persistent or unexplained dizziness should also be investigated rather than left.
Early evaluation often provides reassurance. Where a heart condition is identified, it also allows appropriate treatment to begin.
Where the figures on this page come from
Every figure above is quoted from one of these. This page is general information, not individual medical advice.
More in cardiovascular disease
Related conditions he treats.
- AnginaAngina is a chest pain that comes on when the flow of blood to your heart muscle is reduced, usually because the arteries supplying it have been narrowed by fatty substances. It is a symptom rather than a disease in its own right, and it tends to appear when your heart is asked to work harder, then settle again after a few minutes of rest. Angina is not usually life threatening on its own, but it is a signal worth taking seriously, because it can warn that you are at higher risk of a heart attack or a stroke, and chest pain that is new or has changed its pattern always needs prompt medical assessment.
- Coronary artery diseaseCoronary artery disease, often shortened to CAD, affects the coronary arteries, the blood vessels that supply the heart with oxygenated blood so the muscle can keep pumping. When those arteries become narrowed or blocked, the heart muscle can be left short of the blood it needs. Over time this can lead to worsening symptoms and can cause angina, heart attacks and other serious events.
- Heart attackA heart attack is what happens when a portion of the heart muscle is deprived of blood flow, which is why doctors usually call it a myocardial infarction, or MI. Without fresh blood that area of muscle receives no oxygen and begins to die, so it stops moving and stops pumping efficiently. Heart attacks can be treated if they are detected early, so the symptoms below are worth knowing, and any suspected heart attack is a 999 call rather than something to wait out.
- High blood pressureHigh blood pressure, also known as hypertension, means the force of blood pushing against the walls of your arteries stays consistently too high. Readings of 140/90mmHg or higher when checked by a healthcare professional are classed as hypertensive, against a normal range of 90/60mmHg to 130/85mmHg. It often develops quietly over time without causing any obvious symptoms, which is why regular measurement matters so much.
- StrokeA stroke is a serious, life-threatening condition that occurs when the blood supply to a part of the brain is cut off. The brain needs oxygenated blood to function properly, so any restriction or blockage causes brain cells to die and brain function to be lost. A stroke requires immediate and urgent treatment, so if you think you or someone with you may be having one, call 999 straight away.
- Transient ischaemic attack (TIA)A transient ischaemic attack, usually shortened to TIA, happens when the blood supply to part of the brain is interrupted for a short time. The name explains it, since transient means temporary and ischaemic means a restricted blood supply. The effects pass, but the cause of them does not, which is why a TIA is investigated with the same seriousness as a stroke.