A low blood pressure is anything less than 90/60, according to MayoClinic.com. The top number is the systolic, a measurement of blood pressure when the heart is pumping. The bottom number is the diastolic, the measurement in between heartbeats. Even if the systolic number is in the healthy range but the diastolic is not, a person is diagnosed with low blood pressure. This condition has specific causes, and knowing them helps both doctors and patients keep blood pressure in a healthy range.
Being Pregnant
During the first 24 weeks, many changes take place in a woman's body as it prepares for pregnancy. One of these changes is a rapid expansion of her circulatory system. MayoClinic.com states that this is when a woman's blood pressure is likely to drop, as her body may not have the ability to circulate enough blood right away. Her diastolic pressure can drop as much as 10 to 15 points when this occurs, MayoClinic.com explains.
Heart Conditions
The American Heart Association states that the heart may not be able to circulate enough blood through the bodies of those with certain heart conditions. These conditions include heart valve problems; heart failure; heart attack; and bradycardia, or low heart rate.
Medications
Diastolic pressure can drop due to certain medications people are taking. Diuretics, or drugs to alleviate excess fluid from the body, are one example. Medications for high blood pressure can lower blood pressure too much and may need to be adjusted. Beta-blockers doctors prescribe for heart conditions are another cause, as are drugs to treat erectile dysfunction, according to the American Heart Association.
Becoming Dehydrated
Dehydration is yet another reason for a decline in a person's diastolic pressure, according to MayoClinic.com. When a person is dehydrated, he loses more water than he takes in. In severe cases, a complication---hypovolemic shock---can occur. When it does, a severe drop in diastolic pressure occurs due to low blood volume. A potentially life-threatening complication, death can occur within minutes or hours if not treated.
Loss of Blood
A more obvious cause of low diastolic pressure, any loss of blood can cause blood pressure to drop. This can be from an open wound or internal bleeding.
Anaphylaxis
Anaphylaxis is a severe allergic reaction in people who suffer from food allergies, allergies to bee stings or insect bites, allergies to medications like penicillin, or latex allergies. When their allergies become severe, anaphylaxis occurs, causing swelling of the throat, difficulty breathing, itching and a significant drop in diastolic blood pressure, MayoClinic.com explains.
