Blood pressure readings fall into four general categories, ranging from normal to stage 2 high blood pressure (hypertension). The level of your blood pressure determines what kind of treatment you may need. To get an accurate blood pressure measurement, your doctor should evaluate your readings based on the average of two or more blood pressure readings at three or more office visits.

Your doctor may also use a device called an ophthalmoscope to look at the blood vessels in your eyes. Doctors can see if these vessels have thickened, narrowed, or burst, which may be a sign of high blood pressure. Your doctor will also use a stethoscope to listen to your heart and the sound of blood flowing through your arteries. In some cases, a chest x-ray and electrocardiogram may be needed.
Anyone can develop hypotension, but certain groups of people are more likely to experience it, and there are different types. For instance, orthostatic (positional) hypotension, which occurs when you stand up after sitting or lying down, is more common in older adults. Typically, “your body has certain compensatory mechanisms to prevent your blood pressure from falling when you stand up,” explains Willie Lawrence, MD, an interventional cardiologist at Research Medical Center in Kansas City, Missouri, and a spokesperson for the American Heart Association. But, he adds, “orthostatic hypotension is a problem for some people because these reflexes that should occur, don’t occur.”
Hypertension causes complications such as heart attack and stroke, and these complications are less likely to occur in women who have undergone menopause than men of the same age. When comparing the complication risks of hypertension between men and women aged between 40 and 70 years, it is seen that men are at a higher risk of developing complications than women.
Normal systolic blood pressure is 90 to 119 mm of Hg and normal diastolic blood pressure is 60 to 79 mm Hg. Even in this range, the lower blood pressure is better. So even if one has a blood pressure of 118/78 mm Hg, adopting a healthier lifestyle (quitting smoking, reducing alcohol, reducing weight if obese, exercises, reduced salt intake, healthier diet, etc.) is a good choice. However, self-medications to reduce the blood pressure further should never be attempted.
The World Health Organization has identified hypertension, or high blood pressure, as the leading cause of cardiovascular mortality.[162] The World Hypertension League (WHL), an umbrella organization of 85 national hypertension societies and leagues, recognized that more than 50% of the hypertensive population worldwide are unaware of their condition.[162] To address this problem, the WHL initiated a global awareness campaign on hypertension in 2005 and dedicated May 17 of each year as World Hypertension Day (WHD). Over the past three years, more national societies have been engaging in WHD and have been innovative in their activities to get the message to the public. In 2007, there was record participation from 47 member countries of the WHL. During the week of WHD, all these countries – in partnership with their local governments, professional societies, nongovernmental organizations and private industries – promoted hypertension awareness among the public through several media and public rallies. Using mass media such as Internet and television, the message reached more than 250 million people. As the momentum picks up year after year, the WHL is confident that almost all the estimated 1.5 billion people affected by elevated blood pressure can be reached.[163]

Your doctor may diagnose you with high blood pressure when you have consistent systolic readings of 140 mm Hg or higher or diastolic readings of 90 mm Hg or higher. Based on research, your doctor may also consider you to have high blood pressure if you are an adult or child age 13 or older who has consistent systolic readings of 130 to 139 mm Hg or diastolic readings of 80 to 89 mm Hg and you have other cardiovascular risk factors.

^ Qaseem A, Wilt TJ, Rich R, Humphrey LL, Frost J, Forciea MA (17 January 2017). "Pharmacologic Treatment of Hypertension in Adults Aged 60 Years or Older to Higher Versus Lower Blood Pressure Targets: A Clinical Practice Guideline From the American College of Physicians and the American Academy of Family Physicians". Annals of Internal Medicine. 166 (6): 430–437. doi:10.7326/M16-1785. PMID 28135725.
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.
If dehydration contributes to the problem, increased fluid intake would be needed based in part on your body mass index (BMI). For example, a person with a normal BMI would likely only need eight to ten 8-ounce glasses of water per day to maintain ideal hydration. People with a high BMI may need far more. Adding more salt to your diet may also aid in normalizing your blood pressure.

For example, in a hypertensive patient with asthma, it may be inadvisable to prescribe a beta blocker, as these drugs can aggravate that respiratory condition. Similarly, in patients prone to constipation (the elderly, for example) use of certain calcium channel blockers might best be avoided -- along with diuretics -- as both these classes of drugs can inhibit proper bowel function.
Vasovagal reaction is a common condition in which a healthy person temporarily develops low blood pressure, slow heart rate, and sometimes fainting. A vasovagal reaction typically is brought on by emotions of fear or pain such as having blood drawn, starting an intravenous infusion, or by gastrointestinal upset. Vasovagal reactions are caused by activity of the involuntary (autonomic) nervous system, especially the vagus nerve, which releases hormones that slow the heart and widen the blood vessels. The vagus nerve also controls digestive tract function and senses activity in the digestive system. Thus, some people can have a vasovagal reaction from straining at a bowel movement or vomiting.
However, if a patient has any kind of cardiovascular disease and stage 1 hypertension (a blood pressure over 130 systolic or 80 diastolic), or no existing cardiovascular disease but a significant risk of developing it (over 10% risk within the next 10 years), then lifestyle changes plus medications are recommended. And, even if someone has less than a 10% risk, if their blood pressure is over 140 systolic or 90 diastolic, which is now stage 2 high blood pressure, they ought to be treated with medication as well.
Extremely high levels of blood pressure, i.e. systolic above 180 mm Hg or diastolic above 110 mm Hg requires immediate medical attention. Delayed treatment in such cases may result in various hypertensive emergencies like stroke, heart attack, hypertensive encephalopathy, malignant hypertension, aortic dissection, etc. These conditions may cause death.
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.
Low blood pressure due to nervous system damage (multiple system atrophy with orthostatic hypotension). Also called Shy-Drager syndrome, this rare disorder causes progressive damage to the autonomic nervous system, which controls involuntary functions such as blood pressure, heart rate, breathing and digestion. It's associated with having very high blood pressure while lying down.
Blood pressure (BP) recordings consist of two numbers. The top one is the systolic blood pressure and relates to the contraction of the left side of the heart and the peak pressure achieved when it pumps blood round the body. The bottom number is the diastolic recording and is the lowest pressure achieved in the circulation; this relates to the relaxation of the heart. Blood pressure is measured in millimetres of mercury (mmHg), e.g. 120/70 mmHg.

If your blood pressure is always on the low side and you do not have any of the above symptoms, there is usually no cause for concern. Similarly, if you have a single at-home blood pressure reading that is abnormally low without any symptoms, you probably do not need to see your doctor. It is normal for your blood pressure to rise and fall over time, and your body is usually able to get your blood pressure back to normal.

Hypertension is diagnosed on the basis of a persistently high resting blood pressure. The American Heart Association recommends at least three resting measurements on at least two separate health care visits.[74] The UK National Institute for Health and Care Excellence recommends ambulatory blood pressure monitoring to confirm the diagnosis of hypertension if a clinic blood pressure is 140/90 mmHg or higher.[75]