Adrenal gland testing relies primarily on measuring hormone levels in your blood, urine, or saliva, with the specific test depending on whether your doctor suspects your adrenals are producing too much or too little of a given hormone. There is no single “adrenal test.” Instead, a combination of blood draws, urine collections, and sometimes stimulation or suppression tests builds a picture of how well your adrenal glands are functioning.
Cortisol Blood Tests
Cortisol is the most commonly measured adrenal hormone. Your body follows a predictable daily rhythm: cortisol peaks in the early morning when you wake up and drops to its lowest point around midnight. Because of this pattern, the timing of your blood draw matters as much as the result itself.
A standard cortisol blood test involves two draws in the same day. The first happens between 6 and 8 a.m., when normal levels fall between 10 and 20 mcg/dL. The second draw, taken around 4 p.m., should show a lower reading of 3 to 10 mcg/dL. If your levels don’t follow this expected drop, or if they fall outside normal ranges at either time point, that signals a problem worth investigating further.
24-Hour Urine Cortisol
Instead of capturing cortisol at a single moment, a 24-hour urine collection measures your total cortisol output over a full day. You collect every urine sample across 24 hours in a container your provider gives you. This approach smooths out the natural fluctuations and is particularly useful when screening for cortisol overproduction. In some cases, a single morning urine sample is used instead, though the full-day collection gives a more complete picture.
Late-Night Salivary Cortisol
This is one of the simpler tests and can be done at home. Because cortisol should be at its lowest late at night, an elevated reading at 11 p.m. is a strong signal that your body is making too much. You’ll collect a saliva sample at 11 p.m. on two separate evenings within the same week using tubes provided by your doctor. The test is especially useful for detecting Cushing’s syndrome, a condition caused by prolonged cortisol excess, because the late-night time window is where abnormal production is easiest to spot.
The ACTH Stimulation Test
When adrenal insufficiency (underproduction of cortisol) is suspected, the ACTH stimulation test is considered the gold standard. ACTH is the pituitary hormone that tells your adrenal glands to release cortisol. In this test, a synthetic version of ACTH is injected into a vein or muscle, and then your cortisol is measured at baseline, 30 minutes, and 60 minutes afterward.
Healthy adrenal glands respond by ramping up cortisol production. A normal result is a cortisol level above roughly 18 mcg/dL after stimulation. If cortisol stays flat or barely rises, that points to adrenal insufficiency. Your doctor can then check your natural ACTH levels to determine whether the problem originates in the adrenal glands themselves (primary insufficiency, also called Addison’s disease) or in the pituitary gland, which controls them (secondary insufficiency).
Dexamethasone Suppression Test
While the ACTH stimulation test checks whether your adrenals can produce enough cortisol, the dexamethasone suppression test checks whether they can be told to stop. Dexamethasone is a synthetic steroid that, in a healthy system, signals the brain to dial back cortisol production. If cortisol doesn’t drop after taking dexamethasone, something is overriding that normal feedback loop.
The most common version is the overnight low-dose test. You take a 1 mg tablet of dexamethasone at 11 p.m., then have your blood drawn at 8 a.m. the next morning. A normal result is a morning cortisol level below 1.8 mcg/dL. If your cortisol stays higher than that, your doctor will likely follow up with the high-dose version: 8 mg of dexamethasone at 11 p.m. with another morning blood draw.
The high-dose test helps pinpoint the cause. If cortisol drops by more than 50% after the high dose, the source is most likely a pituitary tumor (Cushing’s disease). If cortisol still doesn’t budge, the overproduction is more likely coming from an adrenal tumor or a hormone-producing tumor elsewhere in the body.
Aldosterone and Renin Testing
Your adrenal glands also produce aldosterone, a hormone that regulates blood pressure by controlling sodium and potassium balance. When a doctor suspects primary aldosteronism, a common cause of resistant high blood pressure, they’ll measure both aldosterone and renin (a kidney enzyme that normally controls aldosterone) and calculate the ratio between them.
This blood draw is typically done in the morning while you’re seated. In the days leading up to the test, you should eat a normal amount of salt rather than restricting it, since low sodium intake can skew results. Your potassium level is measured at the same time, because low potassium can falsely lower your aldosterone reading and mask the condition. Certain blood pressure medications can also interfere with results, so your doctor may adjust your medications temporarily before testing.
Testing for Pheochromocytoma
The inner part of the adrenal gland (the medulla) produces adrenaline and related stress hormones. Pheochromocytomas are rare tumors that cause this part of the gland to overproduce these hormones, leading to episodes of high blood pressure, rapid heartbeat, sweating, and headaches.
The key test measures metanephrines, which are breakdown products of adrenaline. This can be done through a blood draw (plasma metanephrines) or a 24-hour urine collection. Both approaches have similar diagnostic accuracy. The plasma test is more convenient since it requires only a single blood draw, ideally taken while you’re resting in a reclined position to avoid a false elevation from the stress of sitting upright or moving around.
When Imaging Comes In
CT scans and MRIs of the adrenal glands are not first-line tests. Imaging is used after blood or urine results have already confirmed a hormonal abnormality, to locate the source. The exception is when an adrenal mass is found incidentally during a scan done for another reason, which happens fairly often. Current guidelines recommend that every incidentally discovered adrenal mass, even one that looks benign on imaging, should be evaluated with hormone testing to rule out overproduction. A follow-up scan at six months is also standard to confirm the mass hasn’t grown.
Preparing for Adrenal Testing
Several factors can throw off adrenal test results. Stress, illness, pregnancy, oral contraceptives, and steroid medications (including creams and inhalers) all affect cortisol levels. Even your sleep schedule matters, since cortisol’s daily rhythm is tied to your wake-sleep cycle. If you work night shifts, let your doctor know, because the standard morning and afternoon reference ranges may not apply to you.
For the most accurate results, your doctor will likely ask you to fast before morning blood draws, stop certain medications temporarily, and avoid strenuous exercise the day before testing. If you’re collecting saliva at home, you’ll need to avoid eating, drinking, or brushing your teeth for a period before the sample, since even small amounts of blood from irritated gums can contaminate it.