16 May: Q&A with Dr Gordon Williams

What is the difference between hypertension and hypotension?

Dr Gordon Williams, Consultant Cardiologist, Spire Leeds Hospital

Both terms relate to levels of blood pressure (BP).  A person with normal pressure or “tension” within their arteries is described as being ’normotensive’.  If BP is higher than the normal range the person is then ‘hyper’ (more than) i.e. hypertensive.  If BP is lower than normal the term ‘hypo’ (less than) is used i.e. hypotensive.

BP, similar to pulse rate, is never static so there is a range of normality.  It is measured as two figures, a top or maximum value, peaking as the heart reaches its maximum contraction, this being termed ‘systolic’, followed by a lower value reflecting the pressure within the circulation between heart beats, the ‘diastolic’ pressure.  Both values are measured in terms of millimetres of mercury (mmHg). 

High BP below the threshold for hypertension generally is not associated with symptoms; its presence may be missed and recognised only by recording.  With BP values varying several separate recordings may be required to establish the diagnosis of hypertension.  It is influenced by heart rate, stress, anxiety (white coat effect) so isolated readings should not be used to establish the diagnosis.  Values of 120/80 or less are considered normal, with values up to 140/90 considered appropriate to monitor.  Persistently above this the term hypertension applies. 

Hypertension is associated with developing medical complications principally strokes, heart attacks, kidney damage and is linked to progressive dementia, hence diagnosing its presence is so important.

Hypotension with BP values of less than 90/60 may be associated with symptoms of intermittent dizziness.  A brief drop in blood pressure on standing (postural hypotension) is common in both the young and elderly.  Hypotension may reflect the presence of other medical conditions or medications.  BP recorders are less accurate at lower values so more people consider they have hypotension than actually do.

If you have concerns regarding your blood pressure always consult your doctor for clarification.

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The material published on this page is provided for general information only, and should not be treated as a substitute for the professional medical advice of your doctor or other health care professional.

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