A patient is regarded as hypertensive when a thinning of blood vessels causes the magnitude of the force applied by the blood on the arterial walls to increase. This causes the heart to beat faster and harder. This can damage other organs of the body, such as the kidneys, the brain and the eyes, and eventually cause enlargement of the heart itself.

A person is considered to be hypertensive when his blood pressure is higher than 150/90 mmHg, where the upper range is the systolic pressure and the lower range the diastolic pressure. The systolic pressure is the pressure exerted by the blood on the walls of the arteries when the heart is contracting and beating. The diastolic pressure is the pressure exerted by the blood when the heart is relaxed between beats. The former allows blood to flow out of the heart and the latter allows blood to flow into the heart. Blood pressure can be called optimal, normal, high normal or hypertensive. Optimal blood pressure in human beings is less than 120/80mmHg.

High systolic pressure is the cause of cardiovascular problems among middle-aged people and elderly patients, while higher diastolic pressure causes problems in young adults. An increase in systolic pressure itself can cause strokes and heart-attacks.