A hypertensive emergency, unlike the similar sounding hypertensive urgency, is characterized by serious, life-threatening complications. A hypertensive emergency means that the blood pressure is >180 mm Hg or the diastolic pressure is >120 mm Hg, and that end-organ damage is occurring. Signs and symptoms can include shortness of breath, anxiety, chest pain, irregular heart rate, confusion, or fainting. 
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.
Sodium (salt) sensitivity: Some people have high sensitivity to sodium (salt), and their blood pressure increases if they use salt. Reducing sodium intake tends to lower their blood pressure. Americans consume 10-15 times more sodium than they need. Fast foods and processed foods contain particularly high amounts of sodium. Many over-the-counter medicines also contain large amounts of sodium. Read food labels and learn about salt content in foods and other products as a healthy first step to reducing salt intake. Fast food restaurants also make the salt and calorie content of their food available to consumers at their restaurants,
Your total blood pressure reading is determined by measuring your systolic and diastolic blood pressures. Systolic blood pressure, the top number, measures the force your heart exerts on the walls of your arteries each time it beats. Diastolic blood pressure, the bottom number, measures the force your heart exerts on the walls of your arteries in between beats.

For older people, often the first number (systolic) is 130 or higher, but the second number (diastolic) is less than 80. This problem is called isolated systolic hypertension, which is due to age-related stiffening of the major arteries. It is the most common form of high blood pressure in older people and can lead to serious health problems (stroke, heart disease, eye problems, and kidney failure) in addition to shortness of breath during light physical activity, lightheadedness upon standing too fast, and falls. Isolated systolic hypertension is treated in the same way as regular high blood pressure (130 or higher for the first number, or 80 or higher for the second number) but may require more than one type of blood pressure medication. If your doctor determines that your systolic pressure is above a normal level for your age, ask how you can lower it.
Unlike high blood pressure, low blood pressure is defined primarily by signs and symptoms of low blood flow and not by a specific blood pressure number. Some individuals routinely may have blood pressure numbers of 90/50 with no symptoms and therefore do not have low blood pressure. However, others who normally have higher blood pressures may develop symptoms of low blood pressure if their blood pressure drops to 100/60.
NHLBI-funded Research Supports Development of Guidelines for High Blood Pressure Management. The Systolic Blood Pressure Intervention Trial (SPRINT) found that treating to a lower systolic blood pressure target—less than 120 mm Hg—reduced complications from high blood pressure and saved lives. SPRINT results informed recent high blood pressure clinical guidelines that aim to improve treatment for millions of people. SPRINT Memory and Cognition in Decreased Hypertension (SPRINT-MIND) is examining whether treating to the lower blood pressure target can reduce the rate of dementia and slow cognitive decline in the SPRINT participants.
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.
The veins can expand and narrow. When veins expand, more blood can be stored in the veins and less blood returns to the heart for pumping into the arteries. As a result, the heart pumps less blood, and blood pressure is lower. On the other hand, when veins narrow, less blood is stored in the veins, more blood returns to the heart for pumping into the arteries, and blood pressure is higher.
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.

Hi I am currently 9 months pregnant and today I got very hot and felt weak and had excessive sweating. My mom has a digital blood pressure cuff and during this I took it , which was 94/55 with a pulse of 90. It kind of freaked me out so I took another one a couple minutes later which was 105/50 with a pulse of 93. And last one I took was 107/55 with a pulse of 81. Does this sound normal for someone whose pregnant? I always thought high blood pressure was the issue not low. Just very curious, thanks.

Many expert groups recommend a slightly higher target of 150/90 mmHg for those over somewhere between 60 and 80 years of age.[99][100][101][105] The JNC-8 and American College of Physicians recommend the target of 150/90 mmHg for those over 60 years of age,[13][106] but some experts within these groups disagree with this recommendation.[107] Some expert groups have also recommended slightly lower targets in those with diabetes[99] or chronic kidney disease with protein loss in the urine,[108] but others recommend the same target as for the general population.[13][103] The issue of what is the best target and whether targets should differ for high risk individuals is unresolved,[109] although some experts propose more intensive blood pressure lowering than advocated in some guidelines.[110] 

Allergic reaction (anaphylaxis): Anaphylactic shock is a sometimes-fatal allergic reaction that can occur in people who are highly sensitive to drugs such as penicillin, to certain foods such as peanuts or to bee or wasp stings. This type of shock is characterized by breathing problems, hives, itching, a swollen throat and a sudden, dramatic fall in blood pressure.