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.

Bahar Gholipour is a staff reporter for Live Science covering neuroscience, odd medical cases and all things health. She holds a Master of Science degree in neuroscience from the École Normale Supérieure (ENS) in Paris, and has done graduate-level work in science journalism at the State University of New York at Stony Brook. She has worked as a research assistant at the Laboratoire de Neurosciences Cognitives at ENS.

Blood pressure is the force of your blood pushing against the walls of your arteries. Each time your heart beats, it pumps 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 called diastolic pressure.
High blood pressure is a major risk factor for cardiovascular disease. Without treatment, you can have a transient ischemic attack (TIA) or stroke, heart attack, enlarged heart, heart failure, peripheral vascular disease (such as poor circulation and pain in your legs), aneurysms, kidney disease, and broken blood vessels in your eyes. Treatment includes making changes recommended by your healthcare provider.
In the 19th and 20th centuries, before effective pharmacological treatment for hypertension became possible, three treatment modalities were used, all with numerous side-effects: strict sodium restriction (for example the rice diet[152]), sympathectomy (surgical ablation of parts of the sympathetic nervous system), and pyrogen therapy (injection of substances that caused a fever, indirectly reducing blood pressure).[152][158]

Remember that registered users of My HealtheVet can track their blood pressure as part of their Personal Health Record. When you are logged in, the Track Health "Vitals and Readings" section lets you enter your own systolic and diastolic numbers. You can also print out your data as part of your Blue Button report using "Vitals and Readings, Self Reported."
When blood pressure is measured, there are two numbers for each reading: for example, "120 over 80" is written as 120/80. This is because each heartbeat sends a pressure wave through the bloodstream. The higher number (systolic blood pressure) is the peak of the wave, when your heart contracts (the loud "thump" when you listen to your heartbeat). The lower number (diastolic blood pressure) is the lower "dip" or trough of the wave, when your heart relaxes.
In most people with established essential hypertension, increased resistance to blood flow (total peripheral resistance) accounts for the high pressure while cardiac output remains normal.[52] There is evidence that some younger people with prehypertension or 'borderline hypertension' have high cardiac output, an elevated heart rate and normal peripheral resistance, termed hyperkinetic borderline hypertension.[53] These individuals develop the typical features of established essential hypertension in later life as their cardiac output falls and peripheral resistance rises with age.[53] Whether this pattern is typical of all people who ultimately develop hypertension is disputed.[54] The increased peripheral resistance in established hypertension is mainly attributable to structural narrowing of small arteries and arterioles,[55] although a reduction in the number or density of capillaries may also contribute.[56]
Important complications of uncontrolled or poorly treated high blood pressure are due to chronic damage that occurs to different organs in the body and include heart attack, congestive heart failure, stroke, kidney failure, peripheral artery disease, and aneurysms (weakening of the walls of an artery, leading to a sac formation or ballooning of the artery wall). Aneurysms can be found in the brain, along the route of the aorta (the large artery that leaves the heart), and other arteries in the abdomen and extremities.
Hypertension is rarely accompanied by symptoms, and its identification is usually through screening, or when seeking healthcare for an unrelated problem. Some people with high blood pressure report headaches (particularly at the back of the head and in the morning), as well as lightheadedness, vertigo, tinnitus (buzzing or hissing in the ears), altered vision or fainting episodes.[20] These symptoms, however, might be related to associated anxiety rather than the high blood pressure itself.[21]
Fludrocortisone . Fludrocortisone is a medication that seems to help most types of low blood pressure. It works by promoting sodium retention by the kidney, thereby causing fluid retention and some swelling, which is necessary to improve blood pressure. But this sodium retention also causes a loss of potassium. So when taking fludrocortisone, it's important to get enough potassium each day. Fludrocortisone has none of the anti-inflammatory properties of cortisone or prednisone and does not build muscle like anabolic steroids.
High blood pressure is a common disease in which blood flows through blood vessels, or arteries, at higher than normal pressures. Blood pressure is the force of blood pushing against the walls of your arteries as the heart pumps blood. High blood pressure, sometimes called hypertension, is when this force against the artery walls is too high. Your doctor may diagnose you with high blood pressure if you have consistently high blood pressure readings.
Hypertension results from a complex interaction of genes and environmental factors. Numerous common genetic variants with small effects on blood pressure have been identified[34] as well as some rare genetic variants with large effects on blood pressure.[35] Also, genome-wide association studies (GWAS) have identified 35 genetic loci related to blood pressure; 12 of these genetic loci influencing blood pressure were newly found.[36] Sentinel SNP for each new genetic locus identified has shown an association with DNA methylation at multiple nearby CpG sites. These sentinel SNP are located within genes related to vascular smooth muscle and renal function. DNA methylation might affect in some way linking common genetic variation to multiple phenotypes even though mechanisms underlying these associations are not understood. Single variant test performed in this study for the 35 sentinel SNP (known and new) showed that genetic variants singly or in aggregate contribute to risk of clinical phenotypes related to high blood pressure.[36] 

Researchers at the University of Melbourne and Macquarie University have uncovered unusual activity between neurons controlling breathing and blood pressure during the development of essential hypertension. Essential hypertension, which is high blood pressure with no known cause, affects 30% of the global population and is a major contributor to cardiovascular disease.
The kidney can respond to changes in blood pressure by increasing or decreasing the amount of urine that is produced. Urine is primarily water that is removed from the blood. When the kidney makes more urine, the amount (volume) of blood that fills the arteries and veins decreases, and this lowers blood pressure. If the kidneys make less urine, the amount of blood that fills the arteries and veins increases and this increases blood pressure. Compared with the other mechanisms for adjusting blood pressure, changes in the production of urine affect blood pressure slowly over hours and days. (The other mechanisms are effective in seconds.)

Dizziness : While dizziness can be a side effect of some blood pressure medications, it is not caused by high blood pressure. However, dizziness should not be ignored, especially if the onset is sudden. Sudden dizziness, loss of balance or coordination and trouble walking are all warning signs of a stroke. High blood pressure is a leading risk factor for stroke.
^ Jump up to: a b c d e National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents (August 2004). "The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents". Pediatrics. 114 (2 Suppl 4th Report): 555–76. doi:10.1542/peds.114.2.S2.555. PMID 15286277.
Effective lifestyle modification may lower blood pressure as much as an individual antihypertensive medication. Combinations of two or more lifestyle modifications can achieve even better results.[87] There is considerable evidence that reducing dietary salt intake lowers blood pressure, but whether this translates into a reduction in mortality and cardiovascular disease remains uncertain.[96] Estimated sodium intake ≥6g/day and <3g/day are both associated with high risk of death or major cardiovascular disease, but the association between high sodium intake and adverse outcomes is only observed in people with hypertension.[97] Consequently, in the absence of results from randomized controlled trials, the wisdom of reducing levels of dietary salt intake below 3g/day has been questioned.[96]
Hypertension may not produce any symptoms, even if you have had it for years. That's why it is sometimes referred to as a "silent killer." It's estimated that 1 out of every 5 people with high blood pressure aren't aware that they have this major risk factor for strokes and heart attacks. If not properly treated, high blood pressure can damage the heart and circulation, lungs, brain, and kidneys without causing noticeable symptoms. Symptoms of high blood pressure may be present in those who have an extremely high blood pressure. Symptoms of extremely high blood pressure include the following:
Weakened heart muscle can cause the heart to fail and reduce the amount of blood it pumps. One common cause of weakened heart muscle is the death of a large portion of the heart's muscle due to a single, large heart attack or repeated smaller heart attacks. Other examples of conditions that can weaken the ability of the heart to pump blood include medications toxic to the heart, infections of the muscle of the heart by viruses (myocarditis), and diseases of the heart's valves such as aortic stenosis that reduce the flow of blood from the heart and into the arteries.
*Your diet is an important part of blood pressure control. The Dietary Approaches to Stop Hypertension (DASH) eating plan and limiting sodium (salt) help control blood pressure. Ask your doctor to refer you to a dietitian for specific dietary guidelines. More information is available from the National Heart, Lung and Blood Institute at www.nhlbi.nih.gov or the American Heart Association at www.americanheart.org.*

The guidelines, from the American Heart Association (AHA) and the American College of Cardiology (ACC), now define high blood pressure as 130 mm Hg or higher for the systolic blood pressure measurement, or 80 mm Hg or higher for the diastolic blood pressure measurement. (Systolic is the top number, and diastolic is the bottom number, in a blood pressure reading.) Previously, high blood pressure was defined as 140 mm Hg or higher for the systolic measurement and 90 or higher for the diastolic measurement.

High blood pressure is a common disease in which blood flows through blood vessels, or arteries, at higher than normal pressures. Blood pressure is the force of blood pushing against the walls of your arteries as the heart pumps blood. High blood pressure, sometimes called hypertension, is when this force against the artery walls is too high. Your doctor may diagnose you with high blood pressure if you have consistently high blood pressure readings.
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