Hypertension, commonly known as high blood pressure, is typically classified into stages based on the severity of the condition and the level of blood pressure readings. The American College of Cardiology (ACC) and American Heart Association (AHA) defined the following stages of hypertension:

Normal: Systolic blood pressure (the top number) is less than 120 mm Hg, and diastolic blood pressure (the bottom number) is less than 80 mm Hg.

Elevated: Systolic blood pressure ranges from 120 to 129 mm Hg, and diastolic blood pressure is less than 80 mm Hg.

Stage 1 Hypertension: Systolic blood pressure ranges from 130 to 139 mm Hg, or diastolic blood pressure ranges from 80 to 89 mm Hg.

Stage 2 Hypertension: Systolic blood pressure is 140 mm Hg or higher, or diastolic blood pressure is 90 mm Hg or higher.

Hypertensive Crisis: This is a severe stage where blood pressure readings are significantly high and require immediate medical attention. In this stage, systolic blood pressure is usually higher than 180 mm Hg, and/or diastolic blood pressure is higher than 120 mm Hg. Hypertensive crisis requires prompt medical intervention to avoid potential organ damage.