Cortisol AM · low result
Low cortisol: symptoms, what it means, causes and the tests for adrenal insufficiency
Short answer
A low morning cortisol — below about 3 mcg/dL at 8 a.m. — strongly suggests adrenal insufficiency; values between 3 and 15 are indeterminate and need an ACTH (cosyntropin) stimulation test. The most common cause by far is a steroid medicine suppressing the adrenal glands, followed by opioids; Addison's disease, pituitary disease and the hypophysitis caused by cancer immunotherapy are the uncommon ones. An afternoon draw is normally low and means nothing. Adrenal crisis — vomiting, abdominal pain, confusion and low blood pressure — is an emergency.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- Vomiting, severe abdominal pain, confusion, fainting or a very low blood pressure in someone with a low cortisol or on long-term steroids — adrenal crisis; emergency care and intravenous hydrocortisone
- Anyone on long-term steroids who stops them abruptly or becomes acutely ill and cannot keep tablets down — same-day care
What is the normal range for Cortisol AM?
- age 18+, drawn 6–10 AM: 6.2 – 19.4 mcg/dL
Can reflect adrenal insufficiency or recent steroid use.
Full reference table, citations and testing options: Cortisol AM biomarker page.
What are the common causes of low Cortisol AM?
- Timing — cortisol falls through the day and is normally low in the afternoon and evening; a 4 p.m. result is not a morning result
- Glucocorticoid medicines suppressing the adrenal glands — prednisone for more than three weeks, high-dose inhaled steroids, steroid joint injections, potent skin creams, and 'supplements' with hidden steroids; and recent withdrawal from any of them
- Opioids — chronic opioid use suppresses the pituitary ACTH signal (opioid-induced adrenal insufficiency)
- Primary adrenal insufficiency (Addison's disease) — autoimmune destruction of the adrenal glands in 80–90% of US cases; tuberculosis, adrenal hemorrhage, infiltration, adrenoleukodystrophy and drugs such as ketoconazole, mitotane and etomidate
- Secondary adrenal insufficiency — pituitary tumors, surgery or radiation, postpartum pituitary infarction (Sheehan's), head injury, and hypophysitis from immune checkpoint inhibitors (ipilimumab, nivolumab, pembrolizumab)
- Megestrol and medroxyprogesterone, which have glucocorticoid activity and suppress the axis
- Low cortisol-binding globulin — low estrogen states, nephrotic syndrome, cirrhosis and critical illness, where total cortisol is low but free cortisol is normal
- Night-shift work and sleep-phase shifts that move the morning peak
What symptoms go with low Cortisol AM?
- Fatigue and weakness that worsen through the day, loss of appetite and weight, nausea and abdominal pain
- Dizziness on standing and low blood pressure, salt craving, low blood sugar
- Darkening of the skin creases, scars, gums and knuckles in primary (Addison's) disease; pale skin in pituitary disease
- Low mood, poor concentration, joint and muscle aches, loss of body hair and libido in women
What do clinicians usually check next?
- Repeat at 8 a.m. — a value below 3 mcg/dL with symptoms is adrenal insufficiency until proven otherwise; above 15–18 mcg/dL rules it out in most settings
- An ACTH (cosyntropin) stimulation test for indeterminate values: cortisol is measured before and 30–60 minutes after synthetic ACTH; a peak below about 18 mcg/dL (14–15 on newer assays) confirms insufficiency
- Plasma ACTH drawn with the morning cortisol — high in Addison's disease, low or normal in pituitary causes — plus renin and aldosterone, sodium, potassium and glucose
- A complete inventory of steroid exposure (tablets, inhalers, injections, creams, supplements) and of opioid use — the two common, reversible causes
- 21-hydroxylase antibodies when Addison's is confirmed; TSH and free T4, and a pituitary MRI with the other pituitary hormones when ACTH is low
- Anyone diagnosed carries a steroid emergency card and learns sick-day rules; thyroid hormone is never started before cortisol is replaced
Follow-up tests available at TestWell: TSH Test (Thyroid Stimulating Hormone) ($20.99), TSH with Reflex to Free T4 Test ($29.99), TSH + Free T4 Test ($27.99), Aldosterone Test ($61.99), Free T4 Test (Thyroxine) ($20.99), Glucose Test ($14.99).
How do you recheck Cortisol AM?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Men's Hormone Panel | Panel · 7 tests | $199.99 | No | 3–5 business days |
| Metabolism & Weight Loss Panel | Panel · 8 tests | $119.99 | Yes | 2–5 business days |
| Fitness & Performance Panel | Panel · 8 tests | $119.99 | Yes | 2–5 business days |
| Cortisol Test (AM) | Test | $26.49 | No | 2–4 business days |
Common questions
What are the symptoms of low cortisol?
Fatigue that worsens through the day, weakness, loss of appetite and weight, nausea, abdominal pain, dizziness on standing, salt craving and low blood sugar; in Addison's disease the skin creases, scars and gums darken. Adrenal crisis — vomiting, severe abdominal pain, confusion and collapse with low blood pressure — is an emergency.
What causes low cortisol?
Most often a steroid medicine (prednisone, high-dose inhalers, joint injections, potent creams) suppressing the adrenal glands, or chronic opioid use. Addison's disease — autoimmune destruction of the adrenals — and pituitary disease, including the hypophysitis caused by cancer immunotherapy, are the uncommon causes. An afternoon draw is normally low and means nothing.
What level of cortisol is too low?
Below about 3 mcg/dL at 8 a.m. strongly suggests adrenal insufficiency; above 15–18 mcg/dL makes it unlikely; anything between needs an ACTH stimulation test, in which cortisol fails to rise above about 18 mcg/dL after synthetic ACTH. The cut-offs depend on the assay, so the result is read with the laboratory's range and the time of the draw.
Is 'adrenal fatigue' the same as low cortisol?
No. 'Adrenal fatigue' is not a recognised diagnosis and has no test; the Endocrine Society has stated there is no evidence for it. Adrenal insufficiency is a specific, measurable, treatable condition diagnosed with a morning cortisol and an ACTH stimulation test. Tiredness with a normal morning cortisol and a normal stimulation test is not an adrenal problem.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.