In blood pressure readings, “dia” refers to diastolic pressure. Diastolic and systolic readings are expressed as two numbers, one atop the other and divided by a line. The diastolic is the bottom number, and represents the pressure in the blood vessels when the heart is at rest. The top number, the systolic blood pressure, represents the pressure within the blood vessels when the heart is contracting, according to the American Heart Association.
A normal systolic blood pressure is less than 120. When the systolic pressure is between 120 and 139, the person has borderline high blood pressure. When the top number is 140 or greater, the person has high blood pressure, also known as hypertension. Normal diastolic pressure is less than 80. A diastolic blood pressure between 80 and 90 indicates pre-hypertension, while a diastolic blood pressure over 90 indicates hypertension. Elevated blood pressure is a risk factor for heart disease, according to WebMD.
Blood pressure tests are a crucial part of health checkups. Blood pressure tests are painless and are generally performed by a nurse or medical technician. Persons should empty their bladders and refrain from smoking, eating or consuming caffeine for at least one hour prior to a blood pressure test, says Mayo Clinic.