Blood pressure, as defined by the Mayo Clinic, is the pressure of the blood in your arteries. The top number represents the systolic pressure, the pressure in your arteries when your heart is pumping blood. Your bottom number, or diastolic pressure, represents the pressure in your arteries while your heart is at rest.
Currently, a normal blood pressure is 120/80. While this may vary slightly for each person, a considerable or sudden drop in this number can be dangerous, and in some cases life-threatening, according to the Mayo Clinic.
Dehydration
Both the American Heart Association (AHA) and the Mayo Clinic state that dehydration is a possible cause of low blood pressure. The AHA points out that while dehydration may cause a drop in blood pressure, it should not automatically be considered a sign of low blood pressure, as dehydration has a variety of causes. Some of these causes include fever, vomiting, severe diarrhea and an overuse of diuretics (water pills). All of these cause the body to lose more water than it takes in, the prime reason for dehydration.
However, in some cases, a complication of dehydration can arise called hypovolemic shock. According to the Mayo Clinic, this is a life-threatening complication and occurs due to a low volume of blood in your body, resulting in a drop in blood pressure.
Pregnancy
According to the AHA, it is normal for a woman's blood pressure to drop during the first 24 weeks of pregnancy. This is due to her circulatory system expanding at a rapid rate, resulting in both her systolic and diastolic pressures dipping a bit.
A woman's systolic may drop by as much as five to 10 points, while her diastolic can drop between 10 and 15 points, according to the Mayo Clinic. Once a woman has delivered, her pressure typically returns to normal.
Heart Conditions
Certain heart conditions can cause your blood pressure to drop because they prevent the body from circulating enough blood through the body.
Some of the more common heart conditions responsible for a drop in blood pressure include heart valve problems, a low heart rate (known also as bradycardia), heart failure and heart attack.
Anaphylaxis
Anaphylaxis is the medical term used to describe a severe allergic reaction. It also has the potential of being life-threatening and generally occurs in people who are allergic to peanuts, bee stings, penicillin and latex products.
Aside from a sudden drop in blood pressure, other symptoms of anaphylaxis include hives, swelling of the throat, difficulty breathing and itching.
Septic Shock
Referred to medically as septicemia, septic shock occurs when bacteria leaves the original infection site, such as the abdomen, lungs or urinary tract, and finds its way into the bloodstream. The bacteria then produces toxins that affect the blood vessels, eventually leading to a massive drop in blood pressure.
