Hypertension or high blood pressure is a common and deadly health problem, however hypotension or low blood pressure can also cause symptoms. The Mayo Clinic defines blood pressure as the measurement of force in the arteries during the phases of the heartbeat. The first or top number is the systolic pressure, which records the force generated when the heart contracts. The second or bottom number in a blood pressure reading is called the diastolic pressure, which refers to the force in the arteries when the heart is at rest between contractions. Generally, a blood pressure reading of 90/60 or lower is considered low blood pressure. In some cases only the diastolic pressure is low; there are several causes for this.
Heart Disease
The heart directly affects blood pressure and when there are heart problems, these effects arise quickly. The National Heart, Lung and Blood Institute note that heart conditions can cause low systolic and diastolic blood pressure. These heart problems include bradycardia or low heart rate, heart valve problems, a heart attack and heart failure. These conditions reduce blood pressure and the ability of the heart to pump blood throughout the body effectively.
Endocrine Disease
Endocrine diseases affect the organs that produce hormones in the body. These hormones affect the heart and blood pressure and can lower systolic and diastolic pressure. Endocrine diseases include hypothyroidism or an underactive thyroid gland, hyperthyroidism or overactive function of the thyroid, Addison's disease which, affects the adrenal gland, and in some cases diabetes which affects the pancreas. These disorders directly and indirectly cause low blood pressure.
Pregnancy
The LifeClinic.com notes that blood pressure can drop during pregnancy because a woman's circulatory or blood vessel system expands to supply blood to the developing baby. This occurs during the initial 24 weeks of pregnancy. The systolic pressure drops by five to 10 points while the diastolic pressure drops by up to 10 to 15 points. These values may rise later in the pregnancy and will return to normal, pre-pregnancy blood pressure readings after the baby is born.
Dehydration
Dehydration occurs when the body loses more water than it ingests. Even mild levels of dehydration can cause symptoms such as fatigue, drowsiness, dizziness and weakness. More serious levels of dehyration can cause hypovolemic shock, which is a sudden drop in systolic and diastolic blood pressure that can be life-threatening. Causes of mild to severe dehydration include vomiting, severe diarrhea, fever, excess use of diuretics and strenuous exercise or physical activity.
