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.
If you had previously been diagnosed with high blood pressure, the new guidelines don't affect you too much, says Dr. Conlin, as you still need to continue your efforts to lower it through medication, diet, exercise, and weight loss. "However, based on new information in the guidelines, your doctor may propose treating your blood pressure to a lower level," he says.
Normal blood pressure is less than 120/80. Knowing your blood pressure and remembering to check it regularly can help save your life. Choosing healthier, heart-conscious foods, maintaining a healthy weight, getting up and staying active, and managing your stress are great ways to help keep your blood pressure at the level it should be. Learn more about what you can do to help control your blood pressure. 

Even occasional dizziness or lightheadedness may be a relatively minor problem — the result of mild dehydration from too much time in the sun or a hot tub, for example. Still, it's important to see your doctor if you have signs or symptoms of hypotension because they can point to more-serious problems. It can be helpful to keep a record of your symptoms, when they occur and what you're doing at the time.
What about our continued evolution? Are we saying that homo sapiens are stuck in time ? Being a science student I am totally puzzled. Our stomach was never made to digest wheat and rice and so many grains and pulseswe eat now but then this how we evolved from the cave dwelling and flesh eating beings to what we are today. Does any doctor estimated the systolic and diastolic of our ancestors ?

As mentioned earlier, blood pressure increases with age, beginning from infancy to older adulthood. Since most healthy babies and children are typically not at risk for blood pressure problems, most doctors do not check their blood pressure routinely. But, the normal BP range for all adults, regardless of their age, is considered to be lesser than 120/80.

Dietary changes: The health care provider might recommend a diet that includes more vegetables (especially leafy green vegetables), fruits, low-fat dairy products, and fiber-rich foods, and fewer carbohydrates, fats, processed foods, and sugary drinks. He or she also might recommend preparing low-sodium dishes and not adding salt to foods. Watch out for foods with lots of hidden salt (like bread, sandwiches, pizza, and many restaurant and fast-food options).
A sudden fall in blood pressure can be dangerous. A change of just 20 mm Hg — a drop from 110 systolic to 90 mm Hg systolic, for example — can cause dizziness and fainting when the brain fails to receive an adequate supply of blood. And big plunges, such as those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening.
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]

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.

A person consistently showing blood pressure higher than 140/90 over several readings is considered to have hypertension. Doctors advise these people to make effective lifestyle changes to help lower their blood pressure, such as maintaining a healthy weight, including exercise in their daily routine, limiting salt and alcohol intake, and quitting smoking. The doctors will also recommend medication for hypertension depending on how much higher the BP is as compared to the normal blood pressure range and any other health problems that the patient faces.
Pulse pressure (the difference between systolic and diastolic blood pressure) is frequently increased in older people with hypertension. This can mean that systolic pressure is abnormally high, but diastolic pressure may be normal or low a condition termed isolated systolic hypertension.[59] The high pulse pressure in elderly people with hypertension or isolated systolic hypertension is explained by increased arterial stiffness, which typically accompanies aging and may be exacerbated by high blood pressure.[60]
Electrocardiogram (ECG): This tests the heart's electrical activity. This test is more commonly used for patients at high risk of heart problems, such as hypertension and elevated cholesterol levels. The initial ECG is called a baseline. Subsequent ECGs may be compared with the baseline to reveal changes which may point to coronary artery disease or thickening of the heart wall.
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.
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.