I am stressed all the time — should I get my cortisol checked?

Cortisol testing is not particularly useful for everyday stress. The everyday meaning of 'stress' (work pressure, sleep loss, emotional strain) usually does not produce the kind of sustained cortisol changes that lab tests can reliably detect outside of acute illness. Cortisol testing is most useful when there are specific clinical signs of either too little (Addison's) or too much (Cushing's) cortisol production — not for general stress complaints. Many over-the-counter 'cortisol tests' from online vendors have limited clinical value; speak to your doctor about whether testing is appropriate.

Why does my doctor want the test at 8 AM?

Cortisol follows a strong daily rhythm — highest in the early morning, lowest around midnight. A morning value gives the best chance of seeing the peak and is what reference ranges are built around. Samples drawn later in the day can be 50–75% lower even in completely healthy people, which would look like 'low' cortisol without it actually being so.

I have been taking steroids for asthma / arthritis — does that affect cortisol?

Possibly, yes — especially with oral steroids, frequent steroid injections, potent topical steroids over large body areas, or high-dose inhaled steroids over months. Long-term steroid use suppresses the body's own cortisol production. If you stop suddenly or face an acute illness, surgery, or major stress, the suppressed adrenal glands may not respond adequately, which can be dangerous. Doctors usually plan steroid tapers carefully and may arrange cortisol testing or ACTH stimulation testing before stopping.

My cortisol is low — does that mean I have Addison's disease?

Not necessarily from a single test. A morning cortisol below 5 µg/dL is suggestive but not diagnostic. Confirmation usually requires an ACTH stimulation test (also called Synacthen test or cosyntropin test) which measures the adrenal glands' ability to respond to a stimulus — this is the diagnostic standard. The cause also matters — primary adrenal insufficiency (Addison's) is different from secondary adrenal insufficiency (from pituitary causes or steroid withdrawal). ACTH levels alongside cortisol help distinguish.

Do I need to fast for a cortisol test?

Most labs do not strictly require fasting for cortisol. Time of sample (morning, 7:00–9:00 AM) matters far more than fasting. Avoid intense exercise in the hour before the test. Pause biotin supplements for 48–72 hours before. Mention any steroid medications (including topical creams and inhalers), oral contraceptives, hormone therapy, and recent illness to the doctor — all can affect interpretation.

Cortisol Test: Normal Range & What It Shows

Also seen on reports as: Morning Cortisol, AM Cortisol, 8 AM Cortisol, S. Cortisol

What is Cortisol?

Cortisol is the body's main stress hormone, made by the adrenal glands (small glands sitting on top of the kidneys). It is essential for daily life — regulating blood sugar, blood pressure, immune response, fluid balance, and the body's response to stress and illness. Without cortisol, the body cannot maintain itself; with too much, the body develops a recognisable set of changes called Cushing's syndrome.

Cortisol levels follow a strong daily rhythm — highest in the early morning (peaking around 6:00–8:00 AM), falling through the day, and lowest around midnight. This is why time of sample matters substantially. A single morning cortisol gives only one snapshot of a system that varies throughout the day — for diagnostic confirmation, doctors often need more specialised tests.

The test is run on a small blood sample, typically drawn between 7:00 and 9:00 AM. NABL-accredited Indian labs report serum cortisol in micrograms per decilitre (µg/dL) or nanomoles per litre (nmol/L). Salivary cortisol, 24-hour urine cortisol, and dynamic tests (dexamethasone suppression, ACTH stimulation) are used for more specific diagnostic questions.

Why doctors order it

Cortisol is most commonly ordered when symptoms suggest either too little or too much cortisol. Suspected adrenal insufficiency (Addison's disease, secondary adrenal insufficiency from pituitary or hypothalamic causes, or after steroid withdrawal) typically presents with profound tiredness, weight loss, low blood pressure, darkening of skin in some areas, salt cravings, and low blood sodium. Suspected Cushing's syndrome — though much rarer — typically presents with weight gain (particularly around the abdomen and face), purple stretch marks, easy bruising, raised blood pressure, raised blood sugar, and muscle weakness.

It is also ordered in evaluation of unexplained low blood sugar, in patients on long-term steroid therapy who may have suppressed their own cortisol production, in patients being tapered off steroids, in critical illness and ICU monitoring, in some forms of PCOS evaluation, and in suspected pituitary disorders.

Cortisol is sometimes ordered in patients with chronic fatigue, recurrent infections, or stress-related complaints — but a single normal morning cortisol does not by itself rule out adrenal problems, and a slightly low value does not by itself diagnose adrenal insufficiency. Doctors interpret cortisol alongside symptoms, other hormones (ACTH), and sometimes dynamic tests.

What the result means

A morning cortisol firmly within the normal range (typically 10–20 µg/dL) usually argues against significant adrenal insufficiency, particularly when symptoms are mild. A value well below 5 µg/dL on a morning sample is suggestive of adrenal insufficiency and usually warrants confirmation with an ACTH stimulation test, which is the diagnostic standard.

An unexpectedly high morning cortisol can reflect acute illness or stress (cortisol naturally rises in response to physical or emotional stress, recent surgery, or hospitalisation), pregnancy, oral contraceptives or hormone therapy (which raise cortisol-binding globulin), or rarely Cushing's syndrome. Cushing's syndrome diagnosis is rarely made from a single morning cortisol — typical confirmation involves 24-hour urine cortisol, late-night salivary cortisol, or a low-dose dexamethasone suppression test.

Loss of the normal daily rhythm — high cortisol at night when it should be low — is a sensitive sign of Cushing's syndrome and is one of the reasons salivary cortisol at midnight is sometimes used as a screening test. A single morning sample misses this pattern. Borderline morning cortisol in someone on steroid medication (oral, injected, topical, or even inhaled) can reflect partial suppression of the body's own cortisol production rather than a primary adrenal problem.

Reference range

Values in µg/dL. Morning samples (7:00–9:00 AM) are preferred — cortisol naturally falls through the day.

Morning cortisol (7–9 AM) — typical range: Roughly 6 – 23 µg/dL (lab-dependent)
Afternoon / late-day: Lower than morning — daily rhythm is the key
Low morning cortisol: Below ~5 µg/dL — suggests adrenal insufficiency; confirm with ACTH stimulation test
Indeterminate: 5 – 18 µg/dL on a morning sample — neither rules in nor rules out adrenal insufficiency without further tests
Reassuring: Above ~18 µg/dL on a morning sample — usually rules out significant adrenal insufficiency
Cushing's screening tests: 24-hour urine free cortisol, late-night salivary cortisol, or low-dose dexamethasone suppression test — more reliable than single morning value

A single morning cortisol cannot reliably diagnose either adrenal insufficiency or Cushing's syndrome — it screens. Diagnosis usually requires dynamic tests (ACTH stimulation, dexamethasone suppression) and/or specialised samples (24-hour urine cortisol, late-night salivary cortisol). Oral contraceptives and pregnancy raise total cortisol substantially without changing the active free cortisol — pregnancy-specific interpretation applies.

Common factors that affect the result

Time of sample is the dominant factor — cortisol is highest in early morning and lowest at midnight. Samples drawn at 8 PM are typically a quarter or less of the morning value, even in healthy people. This is why most Indian endocrinology centres specify 7:00–9:00 AM for routine cortisol testing.

Acute illness, hospitalisation, recent surgery, fever, and even significant emotional stress raise cortisol substantially — this is the body's normal response. Testing during these times is rarely informative for chronic adrenal problems. Pregnancy raises total cortisol (cortisol-binding globulin increases); oral contraceptives and oestrogen therapy do the same. Free cortisol is less affected.

Medications can dramatically affect cortisol. Any form of steroid — oral (prednisolone), injected (depo-medrol, dexamethasone), topical (potent steroid creams), inhaled (asthma inhalers), or rectal — can suppress the body's own cortisol production over weeks to months. Even apparently 'safe' courses of oral steroids longer than 2–3 weeks can cause secondary adrenal insufficiency on withdrawal. Other medications affecting cortisol: ketoconazole, mitotane, etomidate, opioids, and some chemotherapy. Biotin supplements (popular in Indian beauty supplements) interfere with many cortisol assays.

When to talk to your doctor

You have symptoms suggestive of adrenal insufficiency — profound tiredness, unexplained weight loss, low blood pressure, salt cravings, dizziness on standing, darkening of skin in folds and scars, or unexplained low sodium.
You are recovering from a long course of steroids (oral, injected, or potent topical) and feel persistently unwell — cortisol testing alongside endocrine evaluation may be needed.
You have signs suggesting Cushing's syndrome — central weight gain with thin limbs, purple stretch marks, easy bruising, new-onset diabetes, raised blood pressure, muscle weakness — particularly if developing over a relatively short period.
You are critically ill or in ICU and cortisol is being checked — interpretation in acute illness needs specialist input.
You have been on long-term steroids and are planning to stop, taper, or have surgery or other medical procedures — adrenal coverage usually needs planning.

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