Low Blood Pressure: A Primer

1. What is blood pressure

Blood  pressure  is  a  measurement  of  the  pressure  in  the arteries during the active and resting phases of each heartbeat. The blood pressure  readings  consist  of  two  numbers:  systolic  and  diastolic.

The first (top) number in a blood pressure reading, known as the Systolic pressure, is the amount  of pressure the heart generates when pumping blood through the arteries to the rest of the body.

The second (bottom) number in a blood pressure reading is the Diastolic pressure and  refers to the amount of pressure in the arteries when the heart is at rest between beats.

The  normal  blood  pressure  range is 120/80 mm Hg. 

The blood  pressure  isn’t always  the  same.  It  can vary  considerably  in  a short  amount  of  time  sometimes  from  one heartbeat  to  the  next, depending on body position, breathing rhythm, stress level, physical  condition, medications, time of day, etc. Blood pressure is usually lowest during a period of rest and rises sharply following activity.

2. Low blood pressure

The medical term for low blood pressure is hypotension. What is considered an abnormally low blood pressure for one person may be normal for someone else. Most doctors consider chronically low blood pressure too low only if it causes noticeable symptoms. Some  experts  define  low  blood  pressure  as  readings  lower than  90  mm  Hg  systolic  or  60  mm  Hg  diastolic. you  need  to have only one number in the low range for your blood pressure to be considered lower than normal. In other words, if your systolic pressure is a perfect 115, but your diastolic pressure is 50, you're considered to have lower than normal pressure.

A  sudden  fall  in  blood  pressure  also  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. Any  big  plunges,  especially  those  caused  by  uncontrolled  bleeding,  severe  infections  or  allergic  reactions,  can  be  life threatening. Athletes and people who exercise regularly tend to have a lower blood pressure and a slower heart rate than do people who aren't as fit. So, in general, do non-smokers and people who eat a healthy diet and maintain a normal weight. But in some rare instances, low blood pressure can be a sign of  serious, even life-threatening disorders.

3. Symptoms

In  many  instances, low  blood  pressure isn’t  serious.  If  you have  consistently  low readings but feel fine, you  may  not  go  to a  doctor.  You  must recognize,  however, that the causes of low 

blood  pressure  can range  from  trivial  to the serious.  The secret is to find out what’s causing your condition so that it can be properly  treated. If you have any of the following signs and symptoms,  this could be a signal of an underlying problem:

• Feeling dizzy, lightheaded, or faint.
• Feeling sick to your stomach or vomiting.
• Feeling more thirsty than usual.
• Having blurry vision.
• Feeling weak.
• Being confused.
• Lack of concentration.
• Feeling depressed

If low blood pressure causes lack of blood flow to the organs of the body, then those organs will start to fail. This may result in stroke, heart attack, kidney failure, and bowel ischemia (decreased blood supply to the small and large intestine).

Shock and death are the end result of prolonged low blood pressure. But usually, low blood pressure with no symptoms requires little intervention.

4. Causes

There are a number of potential causes of low blood pressure. In some cases, the underlying condition will need to be treated to correct low blood pressure.

Some of the most common causes include:

• nutritional deficiencies
• prolonged bed rest
• pregnancy
• medications
• severe infections
• allergic reactions
• fall in blood volume
• heart issues

However, low blood pressure can also be an indicator of good health if a person is not experiencing any symptoms.

5. Diagnosis and treatment

Please visit the following link for detailed information related to diagnosis and treatment of low blood pressure

Mayo Clinic