Cortisol (serum, random or 8 AM)

Pick Ordered or Not ordered to see the note.

Indicated when

• —Suspected primary or secondary adrenal insufficiency: unexplained weight loss, orthostatic hypotension, hyperpigmentation (primary AI), low sodium or high potassium, hypoglycemia, or chronic glucocorticoid or opioid exposure carrying suppression risk [1, 3]
• —8 AM cortisol used as an initial screen for adrenal insufficiency, with a low value prompting formal corticotropin (ACTH) stimulation testing [1]
• —Acutely unwell patient with predisposing factors for adrenal insufficiency, where a low testing threshold is recommended [1]

Not indicated when

• —Screening for Cushing's syndrome: a random or single serum cortisol is not a validated screening test for cortisol excess [2]
• —Fatigue alone, with no other feature suggestive of adrenal insufficiency or Cushing's syndrome [1, 4]
• —Routine 'adrenal function' screening without directed clinical suspicion [5]

Why not

A single random cortisol has wide diurnal and stress-related variability, so an isolated normal or borderline result neither confirms nor excludes adrenal insufficiency, and a low result out of context can trigger unnecessary corticotropin-stimulation testing and patient anxiety; it is also not sensitive or specific enough to rule Cushing's syndrome in or out on its own [2].

Better first step

For suspected adrenal insufficiency: 8 AM serum cortisol, followed by a formal corticotropin (ACTH) stimulation test if low [1]. For suspected Cushing's syndrome: late-night salivary cortisol, 24-hour urine free cortisol, or a 1 mg overnight dexamethasone suppression test, only with discriminating clinical features present [2].

Typical ND rationale

An ND may order a random or AM cortisol as a first check on 'adrenal function' in a patient with fatigue, poor stress tolerance, or disrupted sleep, reasoning that cortisol drives energy and the stress response, so an abnormal level would explain the symptoms.

Ontario coverage & CONO orderability

OHIP status

insured

Listed by name in the 2026 Schedule of Benefits for Laboratory Services (L303 Cortisol, fee $5.87); insured when ordered by a physician, midwife, or NP who has clinically assessed the patient. When the same test is ordered by a naturopathic doctor it is not an insured service and is billed privately, regardless of this listing (Reg. 552 s.22(1); SOB-LS 2026 preamble).

CONO orderable

Yes — CONO list #45

CONO list item 45, blood: 'Cortisol – bound and unbound, no differentiation.'

Linked conditions

• Adrenal insufficiency ↗
• Cushing's syndrome ↗
• "Adrenal fatigue" ↗

Counselling script

“A single cortisol level isn't a good test for tiredness on its own, because cortisol normally rises and falls through the day. It is the right first test when there are signs of low adrenal function, such as weight loss, dizziness on standing, darkening skin, or long-term steroid or opioid use. I don't see those signs today, so I'd rather look for the more common causes of fatigue, and I'll test it if any of them appear.”

Revisit if

• —New unexplained weight loss
• —Postural dizziness or fainting
• —Salt craving or new skin darkening
• —Persistent nausea, vomiting, or abdominal pain
• —Starting or stopping chronic glucocorticoid or opioid therapy

References

1. [1]Endocrine Society (2016). Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline. link8 AM cortisol as initial screen for primary adrenal insufficiency; diagnostic thresholds
2. [2]Endocrine Society (2008). The Diagnosis of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline. linkolder guidelineRandom serum cortisol is not a validated screening test for Cushing's syndrome; testing requires discriminating features
3. [3]European Society of Endocrinology / Endocrine Society (2024). European Society of Endocrinology and Endocrine Society Joint Clinical Guideline: Diagnosis and therapy of glucocorticoid-induced adrenal insufficiency. linkChronic glucocorticoid exposure carries risk of adrenal insufficiency and warrants testing
4. [4]BMC Endocrine Disorders (2016). Adrenal fatigue does not exist: a systematic review. linkolder guidelineSystematic review of 58 studies: cortisol testing for fatigue produced an almost systematic pattern of conflicting results; 'adrenal fatigue' not substantiated
5. [5]College of Family Physicians of Canada / Choosing Wisely Canada (2026). Family Medicine: Fifteen Tests and Treatments to Question. linkDon't do annual or routine screening blood tests unless directly indicated by the patient's risk profile
6. [6]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026) - L303 Cortisol. linkCortisol (L303) is listed by name in the 2026 OHIP Schedule of Benefits for Laboratory Services
7. [7]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkCommunity lab tests are insured only when ordered under the Schedule by an authorized prescriber
8. [8]Government of Ontario (e-Laws) (2026). Health Insurance Act, R.R.O. 1990, Reg. 552: General, s. 22 (insured laboratory services). linkA lab test is insured only when ordered by a physician, midwife, or NP who has clinically assessed the patient
9. [9]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkTests ordered by anyone other than an authorized provider, including NDs, are not insured services