Blood pressure is the pressure that the blood presses against the walls of arteries. Two numbers associated with measuring blood pressure are obtained when a blood pressure reading is made. The first number is called the systolic number and is given before or above the second number. The systolic pressure reading is an indication of blood pressure when the heart is pushing out blood. The second number is called the diastolic number and is given after or below the systolic reading. The diastolic reading is an indication of blood pressure in between heart beats. A low blood pressure reading can be an indication of a medical problem.
Hypotension
Low blood pressure is a condition also called hypotension, and blood pressure readings can indicate this condition. When the systolic pressure reading is 90 millimeters of mercury (mm Hg) or less, this is an indication of hypotension. When the diastolic pressure reading is 60 mm Hg or less, this is also an indication of hypotension. It should be noted that blood pressure varies between individuals.
Symptoms
Low blood pressure readings might not be an indication that there is a problem with low blood pressure if the readings are not accompanied by other low blood pressure symptoms. But when other low blood pressure symptoms occur along with low blood pressure readings, this can be an indication of an underlying medical problem. The symptoms that are associated with low blood pressure include dizziness, blurred vision, fainting, fatigue, thirst, depression, nausea, lack of concentration, cold, clammy pale skin, and rapid, shallow breathing.
Conditions
There are conditions that can yield low blood pressure readings, like pregnancy. During the first 24 weeks of pregnancy, the systolic pressure can drop 5 to 10 points, and the diastolic pressure can drop 10 to 15 points. These drops are considered normal, though. Heart problems are not normal, however, and can give low blood pressure readings. Endocrine problems such as an overactive or underactive thyroid can cause low blood pressure readings as well. Other conditions that can give low blood pressure readings include dehydration, blood loss, severe infections, severe allergic reactions and a lack of proper nutrients in the diet.
Medications
Medications can also give low blood pressure readings. These medications include diuretics, alpha and beta blockers, some types of antidepressants, certain drugs that are used in the treatment of Parkinson's disease, and Viagra, especially when it is used in conjunction with a heart medication called nitroglycerine.
Types
Low blood pressure readings are indications of hypotension, which are broken down into several types. Postural or orthostatic hypotension occurs when there is a drop in blood pressure when standing up from a sitting or lying down position. Postprandial hypotension happens when there is a drop in blood pressure after eating a meal. Neurally mediated hypotension is a result of incorrect brain signals, a type of miscommunication between the brain and the heart.
There is another type of hypotension that yields low blood pressure readings that is due to damage of the nervous system. This is called Shy-Drager syndrome, otherwise known as multiple system atrophy with orthostatic hypotension.
