Living with low blood pressure: Advice for living with low blood pressure

Understand the medical jargon and tips on how to cope with low BP

What is low blood pressure?

Blood pressure (BP) is measured in millimetres of mercury (mm Hg) e.g. 120/70 mm Hg

Blood pressure recordings consist of 2 numbers:

Systolic – The top number is the systolic blood pressure and relates to the peak pressure in your arteries when blood is pumped around the body (when your heart beats).

Diastolic – The bottom number is the diastolic recording and is the pressure the arterial circulation when the heart is resting (between beats)

Blood pressure measurements and symptoms vary throughout the day and night which is why doctors may prefer to look at recordings over 24 hours rather than a single reading.

Low blood pressure is also known as hypotension. This is usually defined in an adult as a systolic recording of less than 90 mmHg, although it has been suggested that under 110 mmHg is a more appropriate definition in older people.

Blood pressure and heart rate are controlled by the autonomic nervous system (the nervous system that controls bodily functions that we do not have to think about).

There is a lot of overlap between low blood pressure, vasovagal syncope and PoTS (see last paragraph for further detail), and these conditions can exist in one person.

What are the symptoms of low blood pressure?

It is important to recognise that low blood pressure can cause no symptoms at all and is a common normal finding in young people and athletes.

However, in some people, low blood pressure causes symptoms which can significantly interfere with their quality of life.

Table 1 (Gilani 2021)

A drop in systolic BP of 50- 60 mmHg or more is usually associated with loss of consciousness.

Pre-syncope is when patients experience the above symptoms which may or may not lead on to syncope.

What causes low blood pressure?

There are many factors which can contribute to low blood pressure. In some people, they only have one factor e.g. dehydration. In others, there is a combination which add together to cause problems. For example, prolonged standing, heat, alcohol and hyperventilation (over-breathing) may also contribute.

It occurs more often in older people who are taking a lot of medication. However, it can cause symptoms in younger people. There may be underlying medical conditions such as Hypermobile Ehlers-Danlos Syndrome and Hypermobility Spectrum Disorder, Diabetes, Parkinson’s disease, Addison’s disease or Autonomic Failure. Dehydration, hunger*, low body weight and deconditioning (being chronically out of shape/unfit) can reduce blood pressure.

Different types of low blood pressure

There are many different names and definitions for different types of low blood pressure and this can seem very confusing.

Orthostatic hypotension (also called postural hypotension)

This is a fall in systolic BP of at least 20 mm Hg or diastolic BP of 10 mm Hg usually within 3 min of standing up.

‘Orthostatic’ means caused by upright posture; people with low blood pressure mostly have problems when they are standing, and occasionally with sitting up. This is the result of the brain being above the level of the heart.

Head rush (also known as initial orthostatic or postural hypotension)

This occurs within the first 15 seconds of standing up suddenly. The autonomic nervous system usually corrects this fall in BP very quickly and symptoms are usually very short-lived. ‘Head rush’ can occur in young, healthy people.

Neurally mediated hypotension

This is when blood pressure drops because of a change in the activity of the autonomic nervous system.

Vasovagal syncope (also known as neurally mediated syncope, neurocardiogenic syncope, or reflex syncope)

This occurs when this drop in blood pressure and/or heart rate results in fainting.  This may also be referred to as ‘the common faint’ or ‘simple faint’. Your doctor may classify this further into cardioinhibitory or vasodepressor vasovagal syncope:

Situational syncope

This term is used when there is a specific trigger (or situation) provokes vasovagal syncope such as coughing, swallowing, laughing and passing urine or faeces. Fear, pain or blood tests may also be triggers.

‘Shock’

People can suddenly develop hypotension when severely unwell eg due to loss of circulating blood volume (haemorrhage), loss of fluid (burns, dehydration) or when the heart doesn’t pump efficiently (heart failure).  This situation is called ‘shock’ when the low blood pressure results in inadequate blood supply to the body organs.

Post-prandial hypotension

If blood pressure falls as a consequence of eating food, this is called post-prandial hypotension. ‘Prandial’ means related to a meal. This problem is thought to be caused by dilation of blood vessels in the abdominal cavity and increased blood flow to the bowel, which reduces overall blood pressure.

How to manage fainting associated with low BP?

If you feel faint – act immediately! Try to sit or squat down, or better still, lie down and elevate your legs in the air. If you are unable to do this, cross your thighs, clench your buttocks and tummy* muscles and make tight fists. Taking a short walk or rocking up and down on your toes may help. These counter-manoeuvres squeeze blood back up towards the heart and head*.

Drink 2 glasses of water as soon as possible.

PoTS and low blood pressure

The symptoms of PoTS and orthostatic hypotension can be very similar. In fact, a number of people experience both problems at the same time. During a stand test or a tilt table test, people with PoTS have an increase in heart rate of 30 beats per minute or more within 10 minutes of becoming upright (or to more than 120 bpm). Although the definition says that there is no BP drop in PoTS, some people with PoTS can also develop vasovagal syncope with a drop in their BP and, occasionally, heart rate. This is because the abnormalities in the autonomic nervous system that cause PoTS can also cause a drop in BP – see diagram 1 above. This combination of findings is common in Hypermobile Ehlers-Danlos Syndrome and Hypermobility Spectrum Disorder and ME/CFS.

In vasodepressor syncope or presyncope, there may be an increase in heart rate that accompanies the drop in BP. This is called a reactive tachycardia and can look like PoTS. Treatment for both conditions is very similar.

*Currently no available medical evidence but generally accepted by experts.

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