It occurs more often in older people who are taking a lot of medication. However, it can cause symptoms in younger people. There may be underlying medical conditions such as joint hypermobility syndrome, diabetes, parkinson’s disease, addison’s disease or autonomic failure. Dehydration, hunger, low body weight and deconditioning (being out of shape/unfit) can reduce blood pressure.
If these lifestyle changes don't lower your blood pressure to a safe level, your doctor will also prescribe medicine. You may try several kinds or combinations of medicines before finding a plan that works best for you. Medicine can control your blood pressure, but it can't cure it. You will likely need to take medicine for the rest of your life. Plan with your doctor how to manage your blood pressure.
Patient-activated event recorder: If the episodes of bradycardia or tachycardia are infrequent, a 24-hour Holter recording may not capture these sporadic episodes. In this situation, a patient can wear a patient-activated event recorder for up to 4 weeks. The patient presses a button to start the recording when he or she senses the onset of an abnormal heart rhythm or symptoms possibly caused by low blood pressure. The doctor then analyzes the recordings later to identify the abnormal episodes.
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.
Health issues may happen; however, when a person's blood pressure suddenly drops and their brain is deprived of an adequate blood supply. The condition may lead to lightheadedness or dizziness. A sudden drop in blood pressure usually happens in a person who has risen from a prone or sitting position to a standing one. When this occurs it is referred to as, 'orthostatic hypotension,' or, 'postural hypotension.' Another type of low blood pressure may happen when a person stands for extended periods of time; it is referred to as, 'neurally mediated hypotension.'
Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2017; pii: S0735-1097(17)41519-1. PMID: 29146535
It wasn’t long ago (2013) that those over 60 were advised to aim for blood pressure below 150/90. Now, as a result of a single large trial, the numbers are being revised in a major way. But as Dr. Gilbert Welch has pointed out at , there are problems with this study. First, about 8% of patients aiming for 140 systolic (or less) had “cardiovascular events,” whereas only 6% of those in the 120 systolic group did. This is only a 2 point reduction, but as a percentage it’s a 25% reduction. This is the misleading use of percentage change instead of actual change. Second, the participants were already at higher than average risk for cardiovascular problems, so it was a study of a selected group and not of the general population.
It is important to recognise that low blood pressure can cause no symptoms at all, and is a common normal finding in young people and athletes. However, in some people, low blood pressure causes symptoms which can significantly interfere with their quality of life. These can include syncope (fainting), pre-syncope (near fainting, usually associated with feeling light-headed), sweating, tiredness, slow thinking (brain fog), nausea, visual blurring, hearing disturbances, headache, palpitations, neck pain, breathlessness and chest pain.
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.
Secondary hypertension results from an identifiable cause. Kidney disease is the most common secondary cause of hypertension.[23] Hypertension can also be caused by endocrine conditions, such as Cushing's syndrome, hyperthyroidism, hypothyroidism, acromegaly, Conn's syndrome or hyperaldosteronism, renal artery stenosis (from atherosclerosis or fibromuscular dysplasia), hyperparathyroidism, and pheochromocytoma.[23][47] Other causes of secondary hypertension include obesity, sleep apnea, pregnancy, coarctation of the aorta, excessive eating of liquorice, excessive drinking of alcohol, and certain prescription medicines, herbal remedies, and illegal drugs such as cocaine and methamphetamine.[23][48] Arsenic exposure through drinking water has been shown to correlate with elevated blood pressure.[49][50]
^ Jump up to: a b Go, AS; Bauman, M; King, SM; Fonarow, GC; Lawrence, W; Williams, KA; Sanchez, E (15 November 2013). "An Effective Approach to High Blood Pressure Control: A Science Advisory From the American Heart Association, the American College of Cardiology, and the Centers for Disease Control and Prevention". Hypertension. 63 (4): 878–85. doi:10.1161/HYP.0000000000000003. PMID 24243703. Archived from the original on 20 November 2013. Retrieved 20 November 2013.
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.

Many things can cause your blood pressure to be too low, ranging from normal pregnancy-induced changes to dangerous underlying conditions, like heart problems or hormone disturbances. In some instances, what causes low blood pressure could be a simple case of dehydration brought on by vomiting, intense exercise, or the overuse of diuretics. In fact, even mild dehydration can trigger symptoms such as dizziness, confusion, or other symptoms of low blood pressure.
Hypertension is the most important preventable risk factor for premature death worldwide.[149] It increases the risk of ischemic heart disease,[150] strokes,[23] peripheral vascular disease,[151] and other cardiovascular diseases, including heart failure, aortic aneurysms, diffuse atherosclerosis, chronic kidney disease, atrial fibrillation, and pulmonary embolism.[11][23] Hypertension is also a risk factor for cognitive impairment and dementia.[23] Other complications include hypertensive retinopathy and hypertensive nephropathy.[27]

Low blood pressure is also known as hypotension. This is usually defined in an adult as a systolic recording of less than 90 mmHg, although it has been suggested that for elderly people, below 110 mmHg is a more appropriate definition. Blood pressure and heart rate are controlled by the autonomic nervous system (the nervous system that controls bodily functions that we do not have to think about).                                                                                                                                                                                                
To control or lower high blood pressure, your doctor may recommend that you adopt heart-healthy lifestyle changes, such as heart-healthy eating patterns like the DASH eating plan, alone or with medicines. Controlling or lowering blood pressure can also help prevent or delay high blood pressure complications, such as chronic kidney disease, heart attack, heart failure, stroke, and possibly vascular dementia.
Although the guidelines do not change the traditional definition of high blood pressure, they do call for more aggressive treatment of the condition through the use of a combination of blood-pressure lowering medications. In fact, they say that most people with high blood pressure will require two or more drugs to achieve a blood pressure goal of less than 140/90. The blood pressure goal in people with diabetes or kidney disease should be less than 130/80.
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.
Much of the disease burden of high blood pressure is experienced by people who are not labeled as hypertensive.[87] Consequently, population strategies are required to reduce the consequences of high blood pressure and reduce the need for antihypertensive medications. Lifestyle changes are recommended to lower blood pressure, before starting medications. The 2004 British Hypertension Society guidelines[87] proposed lifestyle changes consistent with those outlined by the US National High BP Education Program in 2002[95] for the primary prevention of hypertension:
Postural hypotension is considered to be a failure of a person's cardiovascular system or nervous system to react appropriately to sudden changes. Usually, when a person stands up, some of their blood pools in their lower extremities. If this remains uncorrected, it would cause the person's blood pressure to fall or decrease. A person's body usually compensates by sending messages to their heart to beat faster and to their blood vessels to constrict, offsetting the drop in blood pressure. If this does not happen, or does not happen quickly enough, postural hypotension is the result.

Medications such as calcium channel blockers, beta blockers, and digoxin (Lanoxin) can slow the rate at which the heart contracts. Some elderly people are extremely sensitive to these medications since they are more likely to have diseased hearts and electrical conduction tissues. In some individuals, the heart rate can become dangerously slow even with small doses of these medications.

Being overweight increases the risk of getting hypertension and increases the workload required of your heart. Diets designed to control blood pressure are often designed to reduce calories as well. Most of these diets require decreasing consumption of fatty foods and sugars while increasing your intake of lean protein, fiber, fruits, and vegetables. A weight loss of just 10 pounds can make a significant difference in your blood pressure. 

With low blood pressure, the patient may feel faint or lose consciousness. This is due to lack of blood flow to the brain, and usually laying the patient supine will help them come round. This is also known as a blackout, and it could be accompanied by a dizzy feeling and light-headedness. Generally, your patient will report trouble focusing, difficulty keeping upright and lack of coordination.