HIGH blood pressure, also known as raised blood pressure or hypertension, is described as a condition in which the blood circulates at persistently raised pressure.
Blood is carried from the heart to all parts of the body and each time the heart beats, it pumps blood around the body.
According to the National Food and Nutrition Centre, blood pressure is created by the force of blood pushing against the inside of blood vessels as it is pumped by the heart.
The centre said blood pressure was expressed in millimetres of mercury (mm Hg) and was recorded as two numbers, usually written one above the other.
It said the top number was the 'systolic' blood pressure or the highest pressure in blood vessels which occured as the heart contracts.
The second or lower number is the diastolic blood pressure — the lowest pressure in blood vessels in between heart beats, when the heart muscle relaxes.
Normal adult blood pressure is defined as a systolic blood pressure of 120mm Hg and a diastolic blood pressure of 80mm Hg.
However, the NFNC said cardiovascular benefits extended to lower systolic (105mm Hg) and lower diastolic blood pressure levels (60mm Hg).
It said hypertension was defined as a systolic blood pressure equal to or above 140mm Hg and/or diastolic blood pressure equal to or above 90mm Hg.
"Maintaining normal ranges of both systolic and diastolic blood pressure are particularly important for the efficient function of vital organs such as the heart, brain and kidneys and for overall health and well-being," said the NFNC in a statement.
"There is a common misconception that people with high blood pressure will always experience symptoms.
"Most people with high blood pressure actually have no symptoms at all and may not even know they have it.
"Sometimes high blood pressure can cause symptoms such as headache, shortness of breath, dizziness, chest pain, palpitations of the heart or nose bleeds.
"If people ignore measuring blood pressure because they think symptoms will alert them to the problem, then it can be dangerous because high blood pressure is often a silent killer."
The NFNC said high blood pressure was the result of many factors, with demographic transition, rapid and unplanned urbanisation and globalisation as the underlying determinants.