Diagnosis

Your doctor will ask questions about your medical history and do a physical examination. The doctor, nurse or other medical assistant will place an inflatable arm cuff around your arm and measure your blood pressure using a pressure-measuring gauge.

Your blood pressure generally should be measured in both arms to determine if there is a difference. It's important to use an appropriate-sized arm cuff.

Blood pressure measurements fall into several categories:

• Normal blood pressure. Your blood pressure is normal if it's below 120/80 mm Hg.
• Elevated blood pressure. Elevated blood pressure is a systolic pressure ranging from 120 to 129 mm Hg and a diastolic pressure below (not above) 80 mm Hg. Elevated blood pressure tends to get worse over time unless steps are taken to control blood pressure. Elevated blood pressure may also be called prehypertension.
• Stage 1 hypertension. Stage 1 hypertension is a systolic pressure ranging from 130 to 139 mm Hg or a diastolic pressure ranging from 80 to 89 mm Hg.
• Stage 2 hypertension. More-severe hypertension, stage 2 hypertension is a systolic pressure of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher.
• Hypertensive crisis. A blood pressure measurement higher than 180/120 mm Hg is an emergency situation that requires urgent medical care. If you get this result when you take your blood pressure at home, wait five minutes and retest. If your blood pressure is still this high, contact your doctor immediately. If you also have chest pain, vision problems, numbness or weakness, breathing difficulty, or any other signs and symptoms of a stroke or heart attack, call 911 or your local emergency medical number.

Both numbers in a blood pressure reading are important. But after age 50, the systolic reading is even more important. Isolated systolic hypertension is a condition in which the diastolic pressure is normal (less than 80 mm Hg) but systolic pressure is high (greater than or equal to 130 mm Hg). This is a common type of high blood pressure among people older than 65.

Because blood pressure normally varies during the day and may increase during a doctor visit (white coat hypertension), your doctor will likely take several blood pressure readings at three or more separate appointments before diagnosing you with high blood pressure.

Taking your blood pressure at home

Your doctor may ask you to record your blood pressure at home to provide additional information and confirm if you have high blood pressure.

Home monitoring is an important way to confirm if you have high blood pressure, to check if your blood pressure treatment is working or to diagnose worsening high blood pressure.

Home blood pressure monitors are widely available and inexpensive, and you don't need a prescription to buy one. Home blood pressure monitoring isn't a substitute for visits to your doctor, and home blood pressure monitors may have some limitations.

Make sure to use a validated device, and check that the cuff fits. Bring the monitor with you to your doctor's office to check its accuracy once a year. Talk to your doctor about how to start checking your blood pressure at home.

Devices that measure your blood pressure at your wrist or finger aren't recommended by the American Heart Association because they can provide less reliable results.

Tests

If you have high blood pressure, your doctor may recommend tests to confirm the diagnosis and check for underlying conditions that can cause hypertension.

• Ambulatory monitoring. This 24-hour blood pressure monitoring test is used to confirm if you have high blood pressure. The device used for this test measures your blood pressure at regular intervals over a 24-hour period and provides a more accurate picture of blood pressure changes over an average day and night. However, these devices aren't available in all medical centers, and they may not be reimbursed.
• Lab tests. Your doctor may recommend a urine test (urinalysis) and blood tests, including a cholesterol test.
• Electrocardiogram (ECG or EKG). This quick and painless test measures your heart's electrical activity.
• Echocardiogram. Depending on your signs and symptoms and test results, your doctor may order an echocardiogram to check for more signs of heart disease. An echocardiogram uses sound waves to produce images of the heart.