Hypertension means high blood pressure. This generally means:

• Systolic blood pressure is consistently over 140 (systolic is the "top" number of your blood pressure measurement, which represents the pressure generated when the heart beats)
• Diastolic blood pressure is consistently over 90 (diastolic is the "bottom" number of your blood pressure measurement, which represents the pressure in the vessels when the heart is at rest)

Either or both of these numbers may be too high.

Pre-hypertension is when your systolic blood pressure is between 120 and 139 or your diastolic blood pressure is between 80 and 89 on multiple readings. If you have pre-hypertension, you are likely to develop high blood pressure at some point. Therefore, your doctor will recommend lifestyle changes to bring your blood pressure down to normal range.

High blood pressure

Blood pressure is determined by the amount of blood pumped by the heart, and the size and condition of the arteries. Many other factors can affect blood pressure, including volume of water in the body; salt content of the body; condition of the kidneys, nervous system, or blood vessels; and levels of various hormones in the body.

Essential hypertension has no identifiable cause. It may be caused by genetics, environmental factors, or even diet, such as how much salt you use.

"Secondary" hypertension is high blood pressure caused by another disorder. This may include:

• adrenal gland tumors
• Cushing's syndrome
• kidney disorders
  • glomerulonephritis (inflammation of kidneys)
  • renal vascular obstruction or narrowing
  • renal failure
• use of medications, drugs, or other chemicals
• oral contraceptives
• hemolytic-uremic syndrome
• Henoch-Schonlein purpura
• periarteritis nodosa
• radiation enteritis
• retroperitoneal fibrosis
• Wilms' tumor

Wang Y, Wang QJ. The prevalence of prehypertension and hypertension among US adults according to the new joint national committee guidelines: new challenges of the old problem. Arch Intern Med. 2004;164(19):2126-34.

Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7). Rockville, Md. National Heart, Lung, and Blood Institute, US Department of Health and Human Services; August 2004. National Institutes of Health Publication No. 04-5230. 

Eyre H, Kahn R, Robertson RM, et al. Preventing cancer, cardiovascular disease, and diabetes: A common agenda for the American Cancer Society, the American Diabetes Association, and the American Heart Association. Circulation. 2004;109(25):3244-55.

Whelton PK, He J, Appel LJ, et al. Primary prevention of hypertension: Clinical and public health advisory from The National High Blood Pressure Education Program. JAMA. 2002;288(15):1882-8.