Another word for “hypertension. ” Blood pressure rises and falls throughout the day. An optimal blood pressure is less than 120/80 mmHg. When blood pressure stays high—greater than or equal to 140/90 mmHg—you have high blood pressure. With high blood pressure, the heart works harder, your arteries take a beating, and your chances of a stroke, heart attack, and kidney problems are greater. Prehypertension is blood pressure between 120 and 139 for the top number, or between 80 and 89 for the bottom number. If your blood pressure is in the prehypertension range, it is more likely that you will develop high blood pressure unless you take action to prevent it.