In adults, the ideal top number (systolic pressure) should be less than 120 mmHg. The bottom number (diastolic pressure) should be less than 80 mmHg.

Prehypertension:

• Top number is consistently 120 to 139 or the bottom number reads 80 to 89.

Stage 1: Mild high blood pressure:

• Top number is consistently 140 to 159 or the bottom number reads 90 to 99.

Stage 2: Moderate to severe high blood pressure:

• Top number is consistently 160 or over or the bottom number reads 100 or over.

Low blood pressure (hypotension):

• Top number reading lower than 90 or pressure 25 mmHg lower than usual

Blood pressure readings may be affected by many different conditions, including:

• Cardiovascular disorders
• Neurological conditions
• Kidney and urological disorders
• Pre-eclampsia in pregnant women
• Psychological factors such as stress, anger, or fear
• Various medications
• "White coat hypertension" may occur if the medical visit itself produces anxiety