Blood pressure is measured with a blood pressure cuff (sphygmomanometer). This may be done using a stethoscope and a cuff and gauge or by an automatic machine. It is a routine part of the physical examination and one of the vital signs often recorded for a patient visit. Other vital signs include pulse rate, respiratory rate (breathing rate), temperature, and weight.
^ Roerecke, Michael; Tobe, Sheldon W.; Kaczorowski, Janusz; Bacon, Simon L.; Vafaei, Afshin; Hasan, Omer S. M.; Krishnan, Rohin J.; Raifu, Amidu O.; Rehm, Jürgen (27 June 2018). "Sex‐Specific Associations Between Alcohol Consumption and Incidence of Hypertension: A Systematic Review and Meta‐Analysis of Cohort Studies". Journal of the American Heart Association. 7 (13): e008202. doi:10.1161/JAHA.117.008202.
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.

Postural hypotension occurs most frequently in people who are taking drugs to control high blood pressure (hypertension). It can also be related to pregnancy, strong emotions, hardening of the arteries (atherosclerosis), or diabetes. The elderly are particularly affected, especially those who have high blood pressure or autonomic nervous system dysfunction.
Adrenal insufficiency, for example, due to Addison's disease, can cause low blood pressure. Addison's disease is a disorder in which the adrenal glands (small glands next to the kidneys) are destroyed. The destroyed adrenal glands can no longer produce sufficient adrenal hormones (specifically cortisol) necessary to maintain normal bodily functions. Cortisol has many functions, one of which is to maintain blood pressure and the function of the heart. Addison's disease is characterized by weight loss, muscle weakness, fatigue, low blood pressure, and, sometimes, darkening of the skin.

Other causes of dehydration include exercise, sweating, fever, and heat exhaustion or heat stroke. Individuals with mild dehydration may experience only thirst and dry mouth. Moderate to severe dehydration may cause orthostatic hypotension (manifested by lightheadedness, dizziness, or fainting upon standing). Prolonged and severe dehydration can lead to shock, kidney failure, confusion, acidosis (too much acid in the blood), coma, and even death.

If your blood pressure is 120/80 millimeters of mercury (mm Hg) or lower, it’s considered normal. Generally, if the blood pressure reading is under 90/60 mm Hg, it is abnormally low and is referred to as hypotension. Some adults regularly have a blood pressure in the hypotensive range, but have no symptoms at all and do not require treatment. In serious cases, though, hypotension can result in a decreased supply of oxygen and nutrients to your brain, which can eventually lead to life-threatening shock.
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]
Stress reduction techniques such as biofeedback or transcendental meditation may be considered as an add-on to other treatments to reduce hypertension, but do not have evidence for preventing cardiovascular disease on their own.[125][126][127] Self-monitoring and appointment reminders might support the use of other strategies to improve blood pressure control, but need further evaluation.[128]