Checking your adrenal glands typically involves a combination of blood tests, urine collection, saliva samples, and sometimes imaging scans. The specific tests your doctor orders depend on whether they suspect your adrenal glands are producing too much or too little of certain hormones. No single test gives the full picture, so most evaluations use at least two or three different methods to confirm a diagnosis.
Physical Signs That Prompt Testing
Before ordering any lab work, doctors look for physical clues that point to adrenal problems. People with underactive adrenal glands often have low blood pressure, darkened patches of skin (especially in skin creases, gums, or scars), fatigue, weight loss, salt cravings, and recurrent abdominal pain. A characteristic finding is orthostatic hypotension, where your blood pressure drops noticeably when you stand up from sitting or lying down.
Overactive adrenal glands produce a different set of signs. Doctors look for thin, fragile skin, wide purple or reddish stretch marks (particularly on the abdomen), swelling, central obesity with thin arms and legs, and muscle wasting. Mood and cognitive changes can accompany either condition. High blood pressure that doesn’t respond well to standard medications can also signal excess aldosterone, the adrenal hormone that controls sodium and potassium balance.
Morning Blood Cortisol Test
The most common starting point is a simple blood draw to measure cortisol, the primary stress hormone your adrenal glands produce. Cortisol follows a predictable daily rhythm, peaking in the early morning and dropping through the afternoon. Because of this, timing matters. Blood is drawn between 6 a.m. and 8 a.m., when normal levels fall between 10 and 20 micrograms per deciliter. By around 4 p.m., normal levels drop to 3 to 10 micrograms per deciliter. A result that falls well outside these ranges in either direction raises a flag for further testing.
Late-Night Saliva Test
If your doctor suspects your adrenal glands are overproducing cortisol (a condition called Cushing syndrome), one of the most convenient screening tools is a late-night salivary cortisol test. You collect a saliva sample at home before bed, typically between 11 p.m. and midnight. Healthy cortisol levels should be at their lowest point at that hour. If levels remain elevated, it suggests your adrenal glands aren’t following their normal daily cycle.
This test has a sensitivity and specificity above 90%, making it a reliable first-line screen. Most doctors will ask you to repeat the collection on at least two separate nights, because two normal results effectively rule out the condition more than 95% of the time. It’s also used as an annual monitoring tool for people who’ve previously been treated for Cushing disease, since recurrence is possible.
Dexamethasone Suppression Test
This test checks whether your body’s cortisol production responds normally to a feedback signal. You take a small pill (a synthetic steroid) between 11 p.m. and midnight. The next morning, between 8 and 9 a.m., your blood is drawn to measure cortisol. In a healthy system, the pill tells the brain to stop signaling the adrenal glands, and cortisol drops. If your morning cortisol stays above 1.8 micrograms per deciliter, that’s considered abnormal and suggests your adrenal glands may be overproducing cortisol independent of normal brain signals. This cutoff catches about 95% of true cases.
There are also longer versions of this test that span two days and use higher doses to help pinpoint whether the problem originates in the adrenal glands themselves or in the pituitary gland in the brain.
ACTH Stimulation Test
When adrenal insufficiency (underactive glands) is the concern, the gold standard is a stimulation test. You receive an injection of a synthetic version of the brain hormone that normally tells your adrenal glands to produce cortisol. Blood is drawn right before the injection and again 30 to 60 minutes later. Healthy adrenal glands respond with a sharp rise in cortisol. If cortisol stays flat or barely increases, it confirms the adrenal glands aren’t functioning properly. The test takes about an hour in a clinic or hospital and doesn’t require fasting.
24-Hour Urine Collection
Some adrenal tests require you to collect all of your urine over a full 24-hour period. This approach measures the total daily output of specific hormones and their breakdown products rather than capturing a single snapshot. It’s used for two main purposes: measuring total cortisol output (called urinary free cortisol) and detecting certain adrenal tumors.
For tumor screening, the lab measures catecholamines and their breakdown products called metanephrines. These are the “fight or flight” hormones your adrenal glands produce. Certain rare tumors (pheochromocytomas and paragangliomas) overproduce these hormones, and the excess shows up reliably in a 24-hour urine sample.
The collection itself takes some planning. You start with an empty bladder, note the time, then collect every drop of urine for the next 24 hours into a special container that needs to stay refrigerated. You should drink at least eight 8-ounce glasses of liquid during the collection period. Starting three days before and continuing through the collection, you’ll need to avoid alcohol, caffeine, chocolate, vanilla-flavored products, bananas, and citrus fruits. Nicotine products, decongestants, cough suppressants, and certain medications (including some stimulants and antidepressants) can also skew results, so your doctor will review your medication list beforehand.
Aldosterone and Renin Blood Test
If high blood pressure is the primary concern, doctors check the ratio of aldosterone to renin in your blood. Aldosterone is the adrenal hormone responsible for telling your kidneys to hold onto sodium and release potassium. Renin is an enzyme your kidneys produce that normally helps regulate aldosterone. When an adrenal problem causes excess aldosterone production (called primary aldosteronism), aldosterone rises while renin drops, creating a characteristically abnormal ratio.
This condition is more common than many people realize and is a significant cause of treatment-resistant high blood pressure. The blood test is straightforward, though your doctor may adjust certain blood pressure medications beforehand since some can interfere with results. A hallmark pattern on routine blood work is low potassium combined with high blood pressure, which often triggers the more specific aldosterone-to-renin ratio test.
Basic Blood Work as an Early Clue
Standard electrolyte panels can offer indirect clues about adrenal function before specialized testing even begins. Because aldosterone drives sodium retention and potassium excretion in the kidneys, persistently low potassium (hypokalemia) alongside high-normal or elevated sodium can suggest excess aldosterone production. In adrenal insufficiency, the pattern reverses: sodium tends to run low while potassium creeps up, because the adrenal glands aren’t making enough aldosterone to maintain the balance. These findings alone don’t confirm an adrenal problem, but they often prompt the more targeted hormone tests described above.
CT Scans and MRI
Imaging comes into play in two situations: when blood or urine tests point to excess hormone production and doctors need to locate the source, or when an adrenal mass is discovered incidentally during a scan done for another reason. The second scenario is surprisingly common. Adrenal abnormalities show up in 5 to 8% of people undergoing CT scans, with the likelihood increasing with age. The vast majority of these incidental findings are benign.
When a mass is found, doctors evaluate its size, density, and whether it’s producing excess hormones. A follow-up CT scan at six months is standard to check whether the mass has grown. Benign growths rarely change size in that window. Any growth is treated as suspicious for malignancy until proven otherwise, and typically leads to further evaluation or surgery. MRI is sometimes used instead of CT, particularly when radiation exposure is a concern or when more detailed tissue characterization is needed.
What to Expect From the Process
Adrenal testing is rarely a single-visit affair. Most evaluations begin with one or two screening tests (often a morning cortisol blood draw combined with either a saliva test or a suppression test), then progress to confirmatory testing if those results are abnormal. The entire workup can take several weeks, partly because some tests need to be repeated for reliability and partly because preparation requirements (like dietary restrictions or medication adjustments) build in waiting time. If imaging is needed, that adds another step. Throughout the process, an endocrinologist typically coordinates which tests to order and in what sequence, based on the specific symptoms and initial results.