Hypertension is when the blood pressure, force exerted by the circulating blood against the arterial wall is too high. Hypertension is diagnosed if, when it is measured on three different days, the systolic blood pressure readings on both days is ≥140 mmHg and/or the diastolic blood pressure readings on both days is ≥90 mmHg. The first (systolic) number represents the pressure in blood vessels when the heart contracts or beats. The second (diastolic) number represents the pressure in the vessels when the heart rests between beats.

Hypertension is a "silent killer". Most people with hypertension are unaware of the problem because it may have no warning signs or symptoms. For this reason, it is essential that blood pressure is measured regularly.

Kuruthi azhal noi is a condition which occurs when the vatham and pitham dosham responsible for blood circulation are affected and causes symptoms like headache, shortness of breath, nose bleeds etc. In siddha system of medicine pitham is increased due to excessive intake of sour, spicy and salty food, mental stress, excessive exposure to heat and sunlight, sleeplessness, uncontrolled anger etc. Thus according to siddha, diet and lifestyle are the major factors which influence the susceptibility to this disease.