Tests may be done for several reasons:
- To detect high blood pressure and confirm its persistence
- To determine whether the cause is an underlying medical condition that can possibly be resolved or controlled
- To evaluate the status of body organs and get a baseline of organ health prior to the start of drug therapies
- To monitor hypertension control and organ status over time
Blood pressure measurement
Blood pressure was traditionally measured using a stethoscope and a blood pressure cuff (called a sphygmomanometer), a device that includes a cuff, a bulb, and a pressure dial that reads the pressure in millimeters of mercury (mm Hg). This is still considered the best method but, more commonly, devices that combine a blood pressure cuff with electronic sensors are used to measure blood pressure. (For more about the procedure, see How is High Blood Pressure Diagnosed? on the National Heart Lung and Blood Institute website.)
Another method is to have the individual wear a device that monitors and records the blood pressure at regular intervals during the day to evaluate blood pressure over time. This is especially helpful during the diagnostic process and can help rule out the high measurements that are sometimes present only when the person is in the doctor's office. (See High Blood Pressure: Using an Ambulatory Blood Pressure Monitor on FamilyDoctor.org.)
These forms of blood pressure measurement are considered indirect. Very rarely, a direct measurement of blood pressure may be required. This can be obtained by inserting a catheter into an artery to measure the pressure inside the blood vessel.
Laboratory testing is not diagnostic for hypertension, but tests are frequently ordered to detect conditions that may be causing and/or exacerbating high blood pressure and to evaluate and monitor organ function over time.
General tests that may be ordered include:
- Urinalysis, urine protein – to help assess kidney function
- Urinary albumin (microalbumin), BUN (blood urea nitrogen) and/or creatinine – to detect and monitor kidney dysfunction or to monitor the effect of medications on the kidneys
- Potassium – as part of the electrolyte panel, which also includes sodium, chloride, and carbon dioxide (CO2); to evaluate and monitor the balance of the body's electrolytes. Cushing syndrome and Conn syndrome often cause low potassium, which can be a clue to their presence. Some high blood pressure medications can upset the balance by causing excessive loss of potassium or potassium retention.
- Fasting glucose, A1c – to help recognize diabetes and to monitor glucose control over time in diabetic patients
- Calcium – to determine how much total calcium or ionized calcium is circulating in the blood; increased activity of the parathyroid glands, which produces an increase in serum calcium, is associated with hypertension.
- TSH (thyroid stimulating hormone) and T4 – to detect and monitor thyroid dysfunction
- Lipid profile – to evaluate levels of total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides and assess the risk of developing atherosclerosis
- The basic metabolic panel (BMP) includes several of the tests listed above, so it may be ordered instead of the individual tests.
Specific tests based on the individual's medical history, physical findings, and routine laboratory test results may be ordered to help detect, diagnose, and monitor conditions causing secondary hypertension. They include:
- Aldosterone and renin – to help detect the overproduction of aldosterone by the adrenal glands (which may be due to a tumor) or renin by the kidneys (which may be due to kidney damage or narrowing of the arteries bringing blood to the kidneys)
- Cortisol – to detect an overproduction of cortisol that may be due to Cushing syndrome
- Catecholamines and metanephrines – to measure epinephrine, norepinephrine, and their metabolites, primarily to help detect the presence of a pheochromocytoma that can cause episodes of severe hypertension
As part of the diagnostic process and to help evaluate the status of vital organs, a health practitioner may order or perform one or more of the following:
- ECG (electrocardiography) – to evaluate the heart rate and rhythm and look for evidence of heart damage
- Eye exam – to look at the retina for changes in the blood vessels (retinopathy) that are caused by prolonged hypertension
- Physical exam – to look for abdominal tenderness, listen for bruits (the sound of blood flowing through a narrowed artery), examine the thyroid gland in the throat for any enlargement or signs of dysfunction, and to detect any other clinical signs as they present
- Imaging scans, such as X-ray or ultrasound of the kidneys or chest X-ray