Moderate hypertension requires initiation of drug therapy. Hypertension is diagnosed if systolic blood pressure is ≥140 mmHg and/or diastolic blood pressure is ≥90 mmHg on 3 non-same day measurements of office blood pressure in the absence of antihypertensive medication. Patients with a previous history of hypertension who have received regular blood pressure-lowering therapy are diagnosed with hypertension despite a blood pressure <140/90 mmHg. In a population with a continuous normal distribution of blood pressure levels, there is no clear line of demarcation between normotension and elevated blood pressure, and the criteria for hypertension are defined based on clinical and epidemiological data. Hypertension is further classified into three levels according to the level of elevated blood pressure. Class I hypertension (mild) is systolic blood pressure 140-159 mmHg and diastolic blood pressure 90-99 mmHg; Class II hypertension (moderate) is systolic blood pressure 160-179 mmHg and diastolic blood pressure 100-109 mmHg; Class III hypertension (severe) is systolic blood pressure ≥180 mmHg and diastolic blood pressure ≥110 mmHg. The above criteria apply to males and females over 18 years of age. For children, the 95th percentile of blood pressure values for different age groups, usually below adult levels, is used. Medication must be initiated for moderate hypertension. Oral calcium antagonists, angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, diuretics, and beta-blockers are available.