Low blood pressure or hypotension should not be confused with blood pressure reading which is merely below the threshold for hypertension (high blood pressure); that is obviously normal and desirable.
Lowish blood pressure usually does not cause any problems and is nothing to worry about. However, excessively low blood pressure may reduce oxygen supply to the brain and the other vital organs, causing symptoms such as dizziness, lightheadedness, fainting and collapses. However, much more frequent – and dangerous – is high blood pressure which is usually asymptomatic. Everybody should therefore get their blood pressure checked at least every five years. The gold standard in blood pressure diagnostic is a 24-hour blood pressure monitor.
Blood pressure is the force generated by the heart with which the blood expands arteries as it is being pumped. If blood pressure is too high, it applies extra strain on the heart and blood vessels, increasing the risk of heart attack, stroke, kidney disease, and many other conditions. Blood pressure measurements are given as two figures: systolic blood pressure and diastolic blood pressure. Systolic blood pressure indicates the pressure taken when the heart contracts to pump the blood into the arteries, and diastolic blood pressure refers to the measurement when the heart relaxes. Blood pressure is measured in millimetres of mercury (mmHg). When you hear from your doctor that your blood pressure is, e.g. 120/80 mmHg ("120 over 80"), it means your systolic blood pressure is 120 mmHg, and the diastolic reading is 80 mmHg.
Blood pressure around 110/60 mmHg to 130/80 mmHg is usually considered normal, while people with readings above 140/90 mmHg are hypertensive. People with blood pressure 90/60 mmHg or below are hypotensive and may suffer from the symptoms mentioned above.
A number of factors can cause low blood pressure, including raised temperature, infection, sepsis (severe infection), pregnancy, some medicines, bleeding, vomiting, diarrhoea, allergic reaction and heart failure. The most common cause is dehydration due to insufficient fluid intake and/or increased loss of fluids.
Low blood pressure usually does not generate any symptoms and therefore does not need any treatment. However, some people may present with dizziness, fainting and recurrent falls, which should trigger appropriate evaluation and treatment. You can follow several simple steps to avoid low blood pressure symptoms: