In its early stages, adrenal insufficiency can be difficult to diagnose. A health care provider may suspect it after reviewing a persons medical history and symptoms.
                
A diagnosis of adrenal insufficiency is confirmed through hormonal blood and urine tests. A health care provider uses these tests first to determine whether cortisol levels are too low and then to establish the cause. Imaging studies of the adrenal and pituitary glands can be useful in helping to establish the cause.
                
A lab technician performs the following tests in a health care providers office, a commercial facility, or a hospital.
                
Hormonal Blood and Urine Tests
                
- ACTH stimulation test. The ACTH stimulation test is the most commonly used test for diagnosing adrenal insufficiency. In this test, the patient is given an intravenous (IV) injection of synthetic ACTH, and samples of blood, urine, or both are taken before and after the injection. The cortisol levels in the blood and urine samples are measured in a lab. The normal response after an ACTH injection is a rise in blood and urine cortisol levels. People with Addisons disease or longstanding secondary adrenal insufficiency have little or no increase in cortisol levels.  Both low- and high-dose ACTH stimulation tests may be used depending on the suspected cause of adrenal insufficiency. For example, if secondary adrenal insufficiency is mild or has only recently occurred, the adrenal glands may still respond to ACTH because they have not yet shut down their own production of hormone. Some studies have suggested a low dose1 microgram (mcg)may be more effective in detecting secondary adrenal insufficiency because the low dose is still enough to raise cortisol levels in healthy people, yet not in people with mild or recent secondary adrenal insufficiency. However, recent research has shown that a significant proportion of healthy children and adults can fail the low-dose test, which may lead to unnecessary treatment. Therefore, some health care providers favor using a 250 mcg ACTH test for more accurate results.   - CRH stimulation test. When the response to the ACTH test is abnormal, a CRH stimulation test can help determine the cause of adrenal insufficiency. In this test, the patient is given an IV injection of synthetic CRH, and blood is taken before and 30, 60, 90, and 120 minutes after the injection. The cortisol levels in the blood samples are measured in a lab. People with Addisons disease respond by producing high levels of ACTH, yet no cortisol. People with secondary adrenal insufficiency do not produce ACTH or have a delayed response. CRH will not stimulate ACTH secretion if the pituitary is damaged, so no ACTH response points to the pituitary as the cause. A delayed ACTH response points to the hypothalamus as the cause.
                
Diagnosis during Adrenal Crisis
                
Although a reliable diagnosis is not possible during adrenal crisis, measurement of blood ACTH and cortisol during the crisisbefore treatment with corticosteroids is givenis often enough to make a preliminary diagnosis. Low blood sodium, low blood glucose, and high blood potassium are also sometimes present at the time of adrenal crisis. Once the crisis is controlled, an ACTH stimulation test can be performed to help make a specific diagnosis. More complex lab tests are sometimes used if the diagnosis remains unclear.