The first chemical for hypertension, sodium thiocyanate, was used in 1900 but had many side effects and was unpopular.[152] Several other agents were developed after the Second World War, the most popular and reasonably effective of which were tetramethylammonium chloride, hexamethonium, hydralazine, and reserpine (derived from the medicinal plant Rauwolfia serpentina). None of these were well tolerated.[159][160] A major breakthrough was achieved with the discovery of the first well-tolerated orally available agents. The first was chlorothiazide, the first thiazide diuretic and developed from the antibiotic sulfanilamide, which became available in 1958.[152][161] Subsequently, beta blockers, calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers, and renin inhibitors were developed as antihypertensive agents.[158]
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Health care providers measure blood pressure with a sphygmomanometer (sfig-mo-muh-NAH-muh-ter), which has a cuff that's wrapped around the upper arm and pumped up to create pressure. When the cuff is inflated, it squeezes a large artery in the arm, stopping the blood flow for a moment. Blood pressure is measured as air is gradually let out of the cuff, which allows blood to flow through the artery again.
Primary (or essential) hypertension is when the cause is unknown. The majority of hypertension cases are primary. When there is an underlying problem such as kidney disease or hormonal disorders that can cause hypertension, it is called secondary hypertension. When it is possible to correct the underlying cause, high blood pressure usually improves and may even return to normal.
^ Jump up to: a b c d e f Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo Jr. JL, Jones DW, Materson BJ, Oparil S, Wright Jr. JT, Roccella EJ, et al. (December 2003). "Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure". Hypertension. Joint National Committee On Prevention. 42 (6): 1206–52. doi:10.1161/01.HYP.0000107251.49515.c2. PMID 14656957. Archived from the original on 20 May 2012. Retrieved 1 January 2012.
Exercise every day. Moderate exercise can lower your risk of high blood pressure. Set some goals so you can exercise safely and work your way up to exercising at least 30 minutes a day most days of the week. Check with your doctor before starting an exercise plan if you have any health problems that are not being treated. You can find more information about exercise and physical activity at Go4Life.
An abnormally fast heart rate (tachycardia) also can cause low blood pressure. The most common example of tachycardia causing low blood pressure is atrial fibrillation (Afib). Atrial fibrillation is a disorder of the heart characterized by rapid and irregular electrical discharges from the muscle of the heart causing the ventricles to contract irregularly and (usually) rapidly. The rapidly contracting ventricles do not have enough time to fill maximally with blood before each contraction, and the amount of blood that is pumped decreases in spite of the faster heart rate. Other abnormally rapid heart rhythms such as ventricular tachycardia also can produce low blood pressure, and sometimes life-threatening shock.
An elevated blood pressure reading means that your blood pressure falls just above the normal level, corresponding to a systolic pressure between 120 and 129 or a diastolic pressure of 80 or less. The new guidelines eliminate the previous category of prehypertension. About one-fourth of Americans have elevated levels and they have two times the risk of heart disease compared with those who have lower blood pressures. Lifestyle changes can help many people with prehypertension lower their blood pressure. 

Understanding the normal BP range with age can help the doctor and you to estimate your cardiovascular health. Blood pressure levels can fluctuate significantly from one reading to the next and it is important to remember that just one abnormally high reading does not signify that you have high blood pressure. Doctors usually use an average of multiple blood pressure readings taken over a period of several days to arrive at a diagnosis of high blood pressure.
Blood pressure is the force of your blood pushing against the walls of your arteries. Each time your heart beats, it pumps out blood into the arteries. Your blood pressure is highest when your heart beats, pumping the blood. This is called systolic pressure. When your heart is at rest, between beats, your blood pressure falls. This is the diastolic pressure. Your blood pressure reading uses these two numbers. Usually they're written one above or before the other, such as 120/80. If your blood pressure reading is 90/60 or lower, you have low blood pressure.