The aldosterone standing test is a very common functional test used clinically in the diagnosis of primary aldosteronism, and is performed by having the patient’s blood drawn in the prone position from 6:00 a.m. to determine basal levels of aldosterone, renin, and angiotensin. The patient is kept in a continuous upright position from 6:00 a.m. to 10:00 a.m., and at the end of the test at 10:00 a.m., blood is drawn again to determine plasma aldosterone, renin, and angiotensin levels in the upright position. In some hospitals, furosemide 40 mg was given along with the stance to improve the diagnostic value of the test.