Yes, cortisol can be measured through blood, saliva, or urine. The type of test your provider orders depends on what they suspect: a simple blood draw can check your baseline levels, while more specialized tests can help diagnose conditions like Cushing’s syndrome or adrenal insufficiency. Here’s what each test involves and what to expect.
Why Timing Matters for Every Cortisol Test
Cortisol follows a predictable daily rhythm that directly affects how test results are interpreted. Levels are highest right when you wake up, then surge another 50 to 60% in the 30 to 40 minutes after waking. From there, cortisol drops steeply through the morning, declines more gradually through the afternoon, and reaches its lowest point around bedtime.
This is why most cortisol blood draws happen at two specific times: once in the morning when levels should be at their peak, and again around 4 p.m. when they should be significantly lower. A single reading without context can be misleading. Stress, poor sleep the night before, and even physical exertion can temporarily spike cortisol, so your provider may ask about your recent sleep and activity before interpreting results.
Blood Test: The Most Common Option
A standard blood draw is the most frequently used cortisol test. A phlebotomist draws blood from a vein in your inner arm, typically in the morning. For adults, healthy morning cortisol generally falls in a range that varies by lab, but levels taken later in the day should be noticeably lower than the morning value. Your provider compares both readings to see whether your cortisol is following its expected daily pattern.
The blood test is straightforward and widely available. It measures total cortisol, which includes both the active form and cortisol bound to proteins in your blood. This distinction matters because certain medications, particularly estrogen-containing birth control pills, increase those binding proteins and can make total cortisol appear artificially high.
Saliva Test: Convenient and Done at Home
Saliva testing is often used to check late-night cortisol, which should be at its lowest point of the day. Your provider gives you a kit with a small swab. You place the swab in your mouth, let it soak with saliva for a couple of minutes, then seal it in the provided container. Some providers ask you to collect multiple samples at different times to map how your cortisol rises and falls throughout the day.
Preparation is simple but specific: don’t eat, drink, brush your teeth, floss, smoke, or vape for 30 minutes before collecting the sample. These activities can contaminate the saliva or alter the reading. Late-night salivary cortisol is particularly useful for screening for Cushing’s syndrome, with studies showing it detects the condition with about 92% sensitivity and 89% specificity, making it a reliable first-pass screening tool.
24-Hour Urine Collection
A urine cortisol test captures your total cortisol output over an entire day rather than a single snapshot. You collect every drop of urine over a 24-hour period into a container provided by your lab. The process starts the morning after your first bathroom trip of the day (which you skip), and continues until the same time the next morning. The normal range for adults is 3.5 to 45 micrograms per 24 hours.
This test measures “free” cortisol, the unbound, active form, which makes it less susceptible to interference from medications that affect binding proteins. The tradeoff is convenience. You need to carry the collection container with you and be careful not to miss any urine over the full 24 hours, which can be impractical for people who work outside the home or travel during that window.
Stimulation and Suppression Tests
When basic cortisol levels come back borderline or your provider suspects a specific condition, they may order a more targeted test that challenges your adrenal glands to respond.
Stimulation Test for Adrenal Insufficiency
This test checks whether your adrenal glands can produce enough cortisol when prompted. You receive a synthetic version of the hormone that normally tells your adrenals to release cortisol. Your blood is drawn 30 and 60 minutes later. Healthy adrenal glands respond with a strong rise in cortisol. If your levels don’t reach the expected threshold, it suggests your adrenals aren’t functioning properly. The result is based on the peak cortisol value reached, not on how much it increased from baseline, because someone who starts with a high baseline from stress may not show a large jump even with healthy adrenal glands.
Suppression Test for Cushing’s Syndrome
This test works in the opposite direction. You take a small steroid tablet at bedtime (between 11 p.m. and midnight), and your blood is drawn between 8 and 9 the next morning. In a healthy person, the tablet signals the body to temporarily shut down its own cortisol production, so the morning reading should be very low. If cortisol remains above 1.7 micrograms per deciliter, the test is considered positive, meaning your body may be overproducing cortisol regardless of normal feedback signals. This is the standard overnight screening test for Cushing’s syndrome.
Medications That Can Skew Results
Several common medications interfere with cortisol testing, particularly with the suppression test. Drugs that speed up the liver’s processing of the test steroid, including certain anti-seizure medications, the antibiotic rifampicin, barbiturates, and alcohol, can cause the steroid to break down too fast. This leads to a falsely normal result even if cortisol production is actually excessive.
On the other side, medications that slow liver processing, including some antifungals, certain HIV medications, and the blood pressure drug diltiazem, can make the test steroid linger longer than expected. This can produce a falsely abnormal result. Providers typically recommend stopping these medications two weeks before testing when safely possible. Estrogen-containing contraceptives also raise cortisol-binding proteins, which inflates total cortisol readings on blood tests. If you’re on any of these medications, mention them before testing so your provider can choose the right test or adjust interpretation accordingly.
Which Test Gets Ordered First
For most people, the process starts with a basic blood or saliva cortisol test. If your provider suspects you’re making too much cortisol, they’ll likely order a late-night salivary cortisol, a 24-hour urine collection, or the overnight suppression test. Often two or three of these are used together because no single test is definitive on its own. If adrenal insufficiency is the concern, a morning blood cortisol that’s clearly low may be enough to move forward, but a stimulation test is usually needed to confirm the diagnosis. The path from screening to diagnosis typically involves repeating abnormal results at least once before starting treatment, since temporary stress, illness, or medication effects can all produce misleading numbers.