Cortisol levels: what high and low results mean and how tests work

What cortisol level is considered high?

There is no single number. The Endocrine Society guideline on diagnosing Cushing's syndrome recommends against using a random blood cortisol to screen for it. Cushing's syndrome is the name for sustained cortisol excess.

Instead, the guideline points to one of three recommended screening tests. Each has its own line, and the guideline algorithm lists these.

Treat these as examples, not universal lines. A 2009 study used 45 µg/24 h for urine and two different salivary cutoffs depending on the assay. Guideline commentary says labs should use method-specific ranges.

One more caveat: the guideline's recommendations rest largely on low-quality evidence. That is common in rare-disease medicine, but it is a reason to expect judgment calls rather than bright lines.

What are the signs of high cortisol, and what causes it?

The signs tend to show up as a cluster, and the most common cause is a medication, not a tumor. NIDDK lists weight gain, a rounder face, fat at the base of the neck or between the shoulders, thin arms and legs, easy bruising, wide purple stretch marks, and muscle weakness.

Women may notice extra facial and body hair and irregular or absent periods. Men may have lower fertility and sex drive and erectile dysfunction. Cleveland Clinic adds high blood pressure, diabetes or prediabetes, and mood changes. Not everyone has all of these, which is part of why it gets missed.

The leading cause overall is long-term, high-dose glucocorticoid medicine, such as drugs for asthma, rheumatoid arthritis, lupus, or transplant rejection, and some joint injections. Doctors rule that out first.

Cushing's that the body produces on its own is rare, roughly 40 to 70 people per million, mostly adults aged 30 to 50 and about three times more often women. About 8 in 10 of those cases come from an ACTH-secreting pituitary tumor. The rest involve tumors elsewhere, most often the lung, or adrenal tumors. It can be mistaken for PCOS or metabolic syndrome.

A milder version, called mild autonomous cortisol secretion, means excess cortisol without classic features. A review reports it in 5 to 50 percent of adrenal incidentalomas, which are adrenal growths found by accident on imaging.

Can high cortisol cause hair loss, anxiety, or high blood pressure?

Blood pressure and mood, yes, in true Cushing's syndrome. Hair loss, we couldn't confirm.

A 2025 review puts hypertension at about 80 percent in endogenous Cushing's. The reverse is rare: among people with high blood pressure, a systematic review of 8 studies found Cushing's in 0 to 7.7 percent. Because hypertension is so common, it tells doctors little on its own.

For mood, reported rates in Cushing's are 50 to 81 percent for major depression and 66 percent for anxiety. Mood disorders can even be the first sign. But a separate review notes that depression and hypertension have low sensitivity and specificity for spotting the disease, so most anxious or depressed people do not have it.

The research we reviewed offers no controlled data tying everyday, stress-level cortisol swings to anxiety. Be skeptical of any claim that your "high cortisol" explains how you feel.

On hair, NIDDK and Cleveland Clinic list excess hair growth in women, not scalp hair loss. We could not verify a causal link, so we are not going to assert one.

What happens when cortisol is too low?

Yes, cortisol can be too low, and it is serious because the body needs it to live. The condition is adrenal insufficiency, and NIDDK describes three types: primary (Addison's disease, from adrenal gland damage), secondary (pituitary ACTH deficiency), and tertiary (hypothalamic CRH deficiency).

Addison's disease affects about 100 to 140 people per million in developed countries; secondary insufficiency, about 150 to 280. The most common cause overall is abruptly stopping long-term corticosteroids. In developed countries, autoimmune disease causes 8 to 9 of 10 Addison's cases.

Symptoms creep in and are easy to wave off: chronic fatigue, muscle weakness, poor appetite, weight loss, abdominal pain, nausea, low blood pressure that drops on standing, salt craving, low blood sugar, and irritability or depression. Addison's can also darken the skin.

The dangerous complication is adrenal crisis. Illness, injury, or surgery raises cortisol needs, and a severe shortfall can cause life-threatening drops in blood pressure, glucose, and sodium, with high potassium. With treatment, most people live normal, active lives.

Diagnosis often uses the cosyntropin (ACTH) stimulation test, the reference standard for primary insufficiency. Cortisol is drawn at baseline, 30, and 60 minutes. A peak below 500 nmol/L (18 µg/dL) is traditionally consistent with insufficiency, though thresholds vary by assay, and newer assays may need lower cutoffs, such as 14 to 15 µg/dL at 30 minutes.

How is cortisol measured, and which test is most accurate?

Doctors use blood, saliva, or urine, and no single test wins. NIDDK says "no one test is perfect," so clinicians generally combine tests rather than rely on one.

• 24-hour urine free cortisol: captures a full day of secretion. A JAMA Internal Medicine review cites sensitivity of 95 to 100 percent and specificity of 94 to 98 percent. Weak spots are collection errors, lab-to-lab range differences, and lower sensitivity for mild cases.
• Late-night salivary cortisol: checks whether the normal bedtime dip is missing. Saliva reflects the active, unbound hormone, and samples can be mailed. Shift work, irregular sleep, tobacco, and licorice can cause false positives.
• 1 mg dexamethasone suppression test: you take dexamethasone around 11 pm to midnight, and blood is drawn at 8 to 9 am. Missed doses, oral contraceptives, pregnancy, kidney disease, and some drug interactions can skew it.
• Blood cortisol: the standard for stimulation and suppression tests, but total cortisol depends on binding proteins, which can distort results.

Context decides the best pick. One NHS protocol calls the main tests broadly equal in accuracy but prefers the overnight dexamethasone test in morbid obesity, depression, alcohol excess, and diabetes, where urine and saliva tests err more.

In a retrospective study of 165 patients with adrenal incidentalomas, late-night salivary cortisol discriminated poorly. Salivary cortisone may do better: in one small study, 9 of 10 patients with autonomous cortisol secretion had elevated late-night cortisone, versus 4 of 10 for cortisol.

Mass spectrometry (LC-MS/MS) is increasingly favored over immunoassays because of cross-reactivity and interference from metabolites and synthetic steroids.

Why one cortisol reading rarely tells the full story

Cortisol is a moving target. For background on the hormone itself, see our cortisol topic page.

It peaks around 8 am and falls to a nadir near 11 pm to midnight, when it is at its lowest in most healthy people. It is also pulsatile, so levels swing within the hour. A review on screening explains why clinic-hours blood draws can't reliably detect a lost rhythm, and why the old 8 am and 4 pm pairing was abandoned.

The JAMA review adds that single morning or evening samples may fail to distinguish Cushing's, since rhythm persists in some patients, and that depression can cause false positives.

False alarms are the bigger risk in people without telltale signs. In the 2009 study, 369 overweight or obese people had no Cushing's despite many abnormal results. Even with two normal tests, combined specificity was only 84 to 90 percent. That is why guidelines call for at least two urine collections or two salivary samples, and why only people with more specific signs should be screened.

Home sampling adds its own noise. In a study of 19 healthy adults, reproducibility of home saliva cortisol and cortisone was moderate, and three to four days of sampling were needed for high reproducibility.

When is a cortisol test done, and who orders it?

Testing follows suspicion, not curiosity. For Cushing's, the guideline supports testing people with multiple, progressive features, especially high-discriminating ones like facial redness, easy bruising, stretch marks, and proximal muscle weakness.

It also covers people with features unusual for their age, such as osteoporosis, hypertension, or type 2 diabetes in the young, and people with an adrenal incidentaloma. Doctors first exclude steroid medicine use.

For low cortisol, triggers include unexplained fatigue, weight loss, low blood pressure, salt craving, recent steroid withdrawal, and pituitary disease.

Initial tests are commonly ordered in primary care. The guideline says abnormal results should go to an endocrinologist, who repeats testing and, if results agree, looks for the cause with ACTH measurement, imaging, and sometimes more specialized tests.

Should you try an at-home cortisol test?

Only if a clinician orders it. Home collection itself is not the problem; unsupervised, unvalidated readings are.

Late-night salivary cortisol is a guideline-endorsed first-line test, and NIDDK notes samples can be collected at home. A 2023 NEJM Evidence study tested home waking salivary cortisone, measured by LC-MS/MS, against the stimulation test in people at high risk of adrenal insufficiency. At cutoffs set for at least 95 percent sensitivity and specificity, negative predictive value was 96 percent and positive predictive value 95 percent. And 83 percent of patients preferred home collection. A Manchester NHS lab now offers it as a screening option.

Timing slips, smoking, licorice, shift work, and odd sleep schedules all muddy results, and single or random readings aren't recommended for Cushing's screening. Screening unselected people produces many false positives. If you have symptoms, see a doctor. If you take steroid medicine, don't stop it abruptly.