High blood pressure, or hypertension, occurs when your blood pressure increases to unhealthy levels. Your blood pressure measurement takes into account how much blood is passing through your blood vessels and the amount of resistance the blood meets while the heart is pumping. Narrow arteries increase resistance. A condition in which the force of the blood against the artery walls is too high.Usually hypertension is defined as blood pressure above 140/90, and is considered severe if the pressure is above 180/120.High blood pressure often has no symptoms. Over time, if untreated, it can cause health conditions, such as heart disease and stroke.Eating a healthier diet with less salt, exercising regularly and taking medication can help lower blood pressure.