The renin test is used to evaluate adrenal glands and if they produce sufficient amounts of aldosterone thereby distinguishing between the potential causes of excess or deficiency. Along with aldostrone it is useful in testing for primary aldosteronism, also known as Conn syndrome, which causes high blood pressure. If the test is positive, aldosterone production may be further evaluated with stimulation and suppression testing.
Both aldosterone and renin levels are highest in the morning and vary throughout the day. They are affected by the body's position, by stress, and by a variety of prescribed medications.