Low Cortisol Symptoms: Causes, Signs & What to Do
Low cortisol, or adrenal insufficiency, causes profound fatigue, low blood pressure, and poor stress tolerance. This page covers the specific symptoms, likely causes, normal ranges, and when to act.
Low cortisol — adrenal insufficiency — is less common than high cortisol but more acutely dangerous. The body cannot mount a normal stress response, blood pressure drops, and energy becomes profoundly impaired. See the Cortisol biomarker overview for how cortisol is tested and what the result reflects.
What Low Cortisol Means
Cortisol is essential for maintaining blood pressure, blood glucose, and immune function, particularly during physical or psychological stress. When cortisol production falls — because the adrenal glands are damaged (primary insufficiency) or because the pituitary is not signaling them (secondary insufficiency) — the body loses its ability to respond normally to any physiologic demand. The result is a characteristic pattern of fatigue, hypotension, and electrolyte disruption.
Symptoms of Low Cortisol
- Profound fatigue that is worst in the morning and disproportionate to activity
- Dizziness or fainting when standing up quickly (orthostatic hypotension)
- Salt cravings
- Low blood pressure
- Nausea, vomiting, or abdominal pain
- Weight loss and poor appetite
- Disproportionate exhaustion during illness, surgery, or other physical stress
- Depression, low mood, and irritability
- Darkening of the skin, gums, and scars (in primary adrenal insufficiency only, from elevated ACTH driving melanin production)
What Causes Low Cortisol
- Addison’s disease: autoimmune destruction of the adrenal cortex (primary insufficiency, most common cause)
- Abrupt withdrawal from long-term corticosteroid medication
- Pituitary insufficiency reducing ACTH output (secondary insufficiency)
- Bilateral adrenal hemorrhage or infarction
- Infections affecting the adrenal glands, including tuberculosis and fungal infections
- Adrenal metastases from other cancers
Normal Cortisol Levels
| Time of Day | Reference Range | |---|---| | Morning (8 AM) | 5-25 mcg/dL | | Evening (4 PM) | 2-9 mcg/dL |
Cortisol follows a diurnal pattern, peaking in the early morning and declining through the day. Results should be interpreted against time-of-collection and the specific test method (serum, saliva, or urine). A single low morning cortisol combined with symptoms warrants formal stimulation testing.
When to See Your Care Team
Book a 1:1 consultation with a licensed care team lead promptly if you have the combination of profound fatigue, dizziness on standing, salt cravings, and skin darkening. Addisonian crisis — acute cortisol deficiency precipitated by illness or injury — is a medical emergency requiring immediate hospital evaluation. Do not manage suspected adrenal insufficiency without clinical supervision.
Frequently Asked Questions
What causes low cortisol?
The most common cause is Addison’s disease, where the immune system attacks the adrenal cortex. The second most common is abrupt cessation of long-term steroid medication, which suppresses the adrenal glands over time. Secondary insufficiency from pituitary disease accounts for a smaller proportion.
What is an Addisonian crisis?
An Addisonian crisis is an acute, life-threatening form of adrenal insufficiency triggered by physiologic stress such as infection, surgery, or injury. It presents with severe hypotension, vomiting, and confusion. It requires emergency glucocorticoid injection and IV fluids.
Does low cortisol cause skin darkening?
Yes, but only in primary adrenal insufficiency. When the adrenal glands fail, ACTH rises in compensation. High ACTH drives melanocyte-stimulating hormone production, causing hyperpigmentation of sun-exposed skin, scars, and mucous membranes. This sign does not occur in secondary insufficiency (pituitary disease), where ACTH is low.
How is low cortisol treated?
Primary and secondary adrenal insufficiency are treated with daily oral hydrocortisone replacement. Doses are increased during illness, surgery, or injury (sick-day rules). Patients also carry injectable hydrocortisone for emergencies.
References
- NIH: Adrenal Insufficiency and Addison’s Disease
- MedlinePlus: Cortisol test
- Cleveland Clinic: Addison’s Disease
