Blood pressure is something most of us are familiar with – but do we really understand what it means? Blood pressure is the way the medical profession measures arterial pressure during both the active and resting phases of a single heartbeat. This pressure can be likened to the pressure of a tyre – too much and there is the danger of damage, too little and things may go a little flat! For humans the normal, expected blood pressure is 120/80 mm Hg.

When a medical practitioner refers to ‘systolic’ blood pressure they are referring to the top number of the equation, this number represents the maximum arterial pressure during contraction of the left ventricle of the heart. The lower, or second, number in a blood pressure reading is referred to as ‘diastolic’ - the time when the heart is at rest and dilated.

A systolic blood pressure reading of below 90 mm Hg (millimetres of mercury) is considered low blood pressure (or hypotension); a diastolic reading of 60 mm Hg or less is also considered too low.

Low blood pressure

Low blood pressure causes the flow of blood to the vital organs of the body to be restricted – for some individuals this may result in a faint. Individuals with a lower than average blood pressure are at decreased risk of major disease and illness, such as stroke, cardiac disease, or kidney disease. Those who undertake regular exercise do not smoke, maintain a healthy weight and athletes tend to have a naturally occurring low blood pressure reading. Provided the pressure is not so low as to cause symptoms, or even damage to the vital organs, low blood pressure may be considered a good thing.

There are a number of symptoms of low blood pressure including the following –

• Fainting
• Shortness of breath
• Light headedness and/or dizziness
• Chest pain
• Cold extremities

What causes low blood pressure?

There are a number of causes for low blood pressure, these include the following –

• Low blood volume, widening of the blood vessels or anaemia
• Hormonal changes
• Side effects of some medications
• Heart disease – including decreased cardiac output, congestive heart failure, myocardial infarction, valve abnormality, heart failure, low heart rate (bradycardia)
• Gland disorders
• Severe injury, shock
• Dehydration

Testing for low blood pressure

An individual will usually discover they have a lower than average blood vessel reading during a routine blood pressure procedure in their doctor’s office. This may be followed, at the doctor’s discretion, by a number of other tests including –

• Monitoring of blood pressure for a number of days or weeks
• Blood tests
• Electrocardiogram
• Echocardiogram

Living with and treating hypotension

Whilst hypotension may be treated with medication, the condition can also be improved by simple lifestyle changes –

• Drink plenty of fluids in order to avoid becoming dehydrated
• Avoid excessive alcohol use – this may contribute to any existing dehydration
• Take care when getting out of hot showers or baths
• Avoid standing up too quickly
• Eat little and often, avoid consuming too many carbohydrates
• Eat a healthy, well balanced diet with a wide variety of foods from each of the major food groups.