For an accurate diagnosis of hypertension to be made, it is essential for proper blood pressure measurement technique to be used.[76] Improper measurement of blood pressure is common and can change the blood pressure reading by up to 10 mmHg, which can lead to misdiagnosis and misclassification of hypertension.[76] Correct blood pressure measurement technique involves several steps. Proper blood pressure measurement requires the person whose blood pressure is being measured to sit quietly for at least five minutes which is then followed by application of a properly fitted blood pressure cuff to a bare upper arm.[76] The person should be seated with their back supported, feet flat on the floor, and with their legs uncrossed.[76] The person whose blood pressure is being measured should avoid talking or moving during this process.[76] The arm being measured should be supported on a flat surface at the level of the heart.[76] Blood pressure measurement should be done in a quiet room so the medical professional checking the blood pressure can hear the Korotkoff sounds while listening to the brachial artery with a stethoscope for accurate blood pressure measurements.[76][77] The blood pressure cuff should be deflated slowly (2-3 mmHg per second) while listening for the Korotkoff sounds.[77] The bladder should be emptied before a person's blood pressure is measured since this can increase blood pressure by up to 15/10 mmHg.[76] Multiple blood pressure readings (at least two) spaced 1–2 minutes apart should be obtained to ensure accuracy.[77] Ambulatory blood pressure monitoring over 12 to 24 hours is the most accurate method to confirm the diagnosis.[78] 

However, the guidelines stress that, for most of the newly classified patients, the recommended treatment will be lifestyle modifications, such as weight loss and changes in diet and exercise levels, as opposed to medications. Only a small increase in the percentage of U.S. adults receiving blood pressure medications — about 2 percent — is expected, the authors said.
Hypertension with certain specific additional signs and symptoms may suggest secondary hypertension, i.e. hypertension due to an identifiable cause. For example, Cushing's syndrome frequently causes truncal obesity, glucose intolerance, moon face, a hump of fat behind the neck/shoulder (referred to as a buffalo hump), and purple abdominal stretch marks.[23] Hyperthyroidism frequently causes weight loss with increased appetite, fast heart rate, bulging eyes, and tremor. Renal artery stenosis (RAS) may be associated with a localized abdominal bruit to the left or right of the midline (unilateral RAS), or in both locations (bilateral RAS). Coarctation of the aorta frequently causes a decreased blood pressure in the lower extremities relative to the arms, or delayed or absent femoral arterial pulses. Pheochromocytoma may cause abrupt ("paroxysmal") episodes of hypertension accompanied by headache, palpitations, pale appearance, and excessive sweating.[23]
Regular visits with your doctor are also key to controlling your blood pressure. If your blood pressure is well-controlled, check with your doctor about how often you need to check it. Your doctor may suggest checking it daily or less often. If you're making any changes in your medications or other treatments, your doctor may recommend you check your blood pressure starting two weeks after treatment changes and a week before your next appointment.