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Low Cortisol Symptoms and Causes: When to Suspect Adrenal Issues

Low cortisol can cause long-lasting fatigue, weakness, weight loss, dizziness on standing, and salt cravings. Learn the causes, which test to get first, and when it is an emergency.

Published

March 27, 2026

Last updated

October 5, 2026

Read time

14 min read

Medically reviewed by

Rhonda Collins, FNP-C

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The most common symptoms of low cortisol (adrenal insufficiency) are long-lasting fatigue, muscle weakness, loss of appetite, weight loss, and abdominal pain. Other signs include nausea, vomiting, dizziness or fainting when you stand up, salt cravings, low blood sugar, joint pain, low mood, and, in women, irregular or missed periods. Symptoms usually build slowly, so they are easy to mistake for other problems [9].

Low cortisol becomes an emergency, called adrenal crisis, when it causes sudden severe pain in the lower back, abdomen, or legs, vomiting, confusion, or fainting. That needs emergency care right away. See When Low Cortisol Becomes an Emergency below [11].

What Are the Symptoms of Low Cortisol?

Low cortisol symptoms overlap with many other conditions, which is why they are often overlooked. The pattern below is what prompts a clinician to test cortisol. Most of these symptoms come from the missing cortisol itself. Salt cravings and darker skin point to primary adrenal insufficiency (Addison’s disease), where the adrenal glands also stop making aldosterone and ACTH rises [4][9].

The most typical complaint is fatigue that does not improve with rest, often together with weight loss and poor appetite. Because these signs come on gradually, some people are first diagnosed during an adrenal crisis [9]. Long-lasting tiredness, weakness, or weight loss without trying is the usual reason to check a morning cortisol.

When Low Cortisol Becomes an Emergency

Adrenal crisis is a life-threatening emergency. It happens when cortisol drops critically low, usually in someone with undiagnosed or undertreated adrenal insufficiency who meets a physical stressor such as an infection, injury, surgery, or dehydration. The body needs much more cortisol than usual at these times [11]. Symptoms include:

• Sudden, severe pain in the lower back, abdomen, or legs

• Vomiting and diarrhea, leading to dehydration

• Severe weakness

• Confusion or loss of consciousness

• Very low blood pressure, low blood sugar, low sodium, and high potassium on testing

If you have these symptoms, call emergency services. Treatment is an injection of a glucocorticoid (usually hydrocortisone) and fluids, given as soon as possible [4][11]. People with diagnosed adrenal insufficiency should carry an emergency glucocorticoid injection and a steroid card or medical alert tag, and make sure family and friends know how to give the injection [4][11].

What Causes Low Cortisol?

Low cortisol has distinct causes depending on where the hypothalamic-pituitary-adrenal (HPA) axis is disrupted. The most common cause of adrenal insufficiency overall is suddenly stopping corticosteroid medicines, such as prednisone, after taking them for a long time [9].

Primary Adrenal Insufficiency (Addison’s Disease)

The adrenal glands themselves are damaged, so they cannot make enough cortisol and often aldosterone. In developed countries, autoimmune disease causes 8 or 9 of every 10 cases: the immune system attacks the adrenal cortex [2][9]. Tuberculosis used to be the most common cause and is now much less common. Other causes include bleeding into the adrenal glands, cancer spread to the adrenals, surgical removal of the adrenal glands, some medicines (certain antifungals and the anesthetic etomidate), and genetic disorders such as adrenoleukodystrophy [4][9].

Secondary Adrenal Insufficiency

The adrenal glands are intact, but the pituitary gland does not make enough ACTH (adrenocorticotropic hormone), the signal that tells the adrenals to make cortisol. Causes include pituitary tumors or infection, bleeding into the pituitary, pituitary surgery, traumatic brain injury, autoimmune disease, and Sheehan syndrome, which is damage to the pituitary after severe bleeding during or after childbirth [3][8][9].

Tertiary Adrenal Insufficiency

The hypothalamus does not make enough corticotropin-releasing hormone (CRH), so the pituitary makes less ACTH. The most common cause is suddenly stopping corticosteroids after long-term use: high doses of these medicines suppress CRH, and the adrenal glands can take months to recover after the medicine stops [9]. The risk depends on the dose, duration, potency, and route of the steroid, and on the individual, which is why long-term steroids are tapered under medical supervision rather than stopped abruptly [7]. Tertiary insufficiency can also follow successful treatment of Cushing’s syndrome [9].

Relative Adrenal Insufficiency

In critical illness, such as sepsis, cortisol demand can outstrip production even in people without known adrenal disease. This is called critical illness-related corticosteroid insufficiency and is managed in intensive care settings [12].

How Is Low Cortisol Diagnosed?

Low cortisol is diagnosed with specific cortisol tests. A standard metabolic panel does not measure cortisol. Exact cut-offs depend on the laboratory’s cortisol assay, so a clinician reads each result against that lab’s method and the time of the draw [4][6].

• Morning serum cortisol with ACTH: Drawn in the early morning, when cortisol should be near its daily peak. The Endocrine Society guideline treats a morning cortisol below about 5 µg/dL (140 nmol/L), together with a raised ACTH, as suggestive of primary adrenal insufficiency until stimulation testing confirms it. A low morning value alone cannot make the diagnosis, because some people without adrenal insufficiency, especially older adults, have low levels [4].

• ACTH stimulation test (cosyntropin test): The standard confirmatory test. Synthetic ACTH is injected, and cortisol is measured before and 30 or 60 minutes later. In the guideline, a peak below about 18 µg/dL (500 nmol/L) indicates adrenal insufficiency, a cut-off it labels assay dependent [4]. That figure comes from older cortisol assays. With newer, more specific assays, researchers proposed a lower cut-off of about 14 to 15 µg/dL, depending on the assay [6].

• Plasma ACTH: Separates primary from secondary insufficiency. In Addison’s disease, ACTH is high because the pituitary is trying to stimulate failing adrenals. In secondary insufficiency, ACTH is low or inappropriately normal [4].

• 21-hydroxylase antibodies: Positive in most people with autoimmune Addison’s disease, which helps identify the cause [4][10].

• Pituitary tests: If the stimulation test is unclear or a pituitary cause is suspected, a specialist may use an insulin tolerance test or a CRH stimulation test, and an MRI of the pituitary [10].

Timing and medicines matter. Cortisol is normally low in the afternoon and evening, so an afternoon result cannot tell normal from deficient. Estrogen and pregnancy raise the protein that carries cortisol, which raises total cortisol, and steroid medicines can suppress or interfere with the result [4][7].

Which Cortisol Test Should You Get First?

If you suspect low cortisol, the usual first test is an early-morning blood cortisol, ideally drawn at the same time as a plasma ACTH [4]. Mito’s Cortisol, AM blood test is drawn between 7 and 9 AM, and the ACTH blood test is also a morning draw, so both can be checked from the same early visit.

• A clearly normal morning result makes adrenal insufficiency less likely, but it does not rule out early or secondary disease on its own [4][10].

• A low or borderline result is a reason for an ACTH stimulation test, which a clinician orders and interprets [4][10].

• Saliva and afternoon cortisol are not the tests to start with. Guideline diagnosis rests on serum cortisol measured in the morning and after stimulation [4]. Four-point salivary cortisol panels, often sold to map an “adrenal fatigue” curve, have given conflicting results in studies of fatigued people [5].

For how a morning draw is scheduled and prepared for, see how to test cortisol levels. For reference ranges by age and sex, see normal cortisol levels by age and sex, and for what each marker measures, see the cortisol and ACTH biomarker pages.

Low Cortisol vs. “Adrenal Fatigue”, What Is Real?

“Adrenal fatigue” is not a recognized medical diagnosis. It was popularized by alternative health practitioners to describe a state of mild, chronic cortisol depletion caused by prolonged stress. A 2016 systematic review of 58 studies found no substantiation for it, and no endocrinology society recognizes it [5].

The symptoms people attribute to adrenal fatigue, such as tiredness, poor concentration, and poor stress tolerance, are real. They just may have a different cause. Possible explanations a clinician may check include:

• True adrenal insufficiency: Rare, but testable with a morning cortisol and ACTH, then a stimulation test.

• Iron deficiency: A common cause of fatigue. Low ferritin can mimic many of the symptoms attributed to cortisol problems.

• Thyroid dysfunction: Hypothyroidism and low cortisol share symptoms such as fatigue and weight change.

• Vitamin D deficiency: Often checked as part of a fatigue workup.

Ideas such as “subclinical” adrenal insufficiency or a “dysregulated” daily cortisol curve are sometimes offered as explanations, but they are not established diagnoses, and the salivary cortisol tests used to look for them have produced conflicting results [5]. The take-home: do not accept “adrenal fatigue” as a diagnosis without proper hormonal testing, and do not dismiss the symptoms either.

What Does Cortisol Actually Do?

Cortisol is made by the adrenal glands, two small glands on top of the kidneys, under the control of the hypothalamic-pituitary-adrenal (HPA) axis. The hypothalamus releases CRH, the pituitary responds with ACTH, and ACTH tells the adrenals to make cortisol [1][11].

Cortisol follows a daily rhythm: it peaks in the early morning, then declines through the afternoon and evening, reaching its lowest point around midnight [1]. This is why the time of a cortisol test matters as much as the number.

Cortisol helps the body:

• Control blood sugar: It stimulates the liver to make glucose, keeping fuel available between meals and during fasting.

• Maintain blood pressure: It supports blood vessel tone and the response to adrenaline and noradrenaline.

• Regulate inflammation: It is the body’s main natural anti-inflammatory hormone.

• Respond to stress: During illness, injury, or surgery, the body needs much more cortisol than usual [11].

When cortisol is chronically low, these functions weaken, which explains most of the symptoms above.

Can Lifestyle Changes Fix Low Cortisol?

No. Confirmed adrenal insufficiency needs medically supervised hormone replacement, typically hydrocortisone, with fludrocortisone added for primary insufficiency, plus a plan for extra doses during illness [4]. Sleep, stress management, diet, and exercise do not treat it. If your question is about everyday cortisol rhythm rather than a diagnosed deficiency, see how to raise cortisol naturally.

Start with a morning cortisol. The Cortisol, AM blood test measures cortisol at its morning peak, and the ACTH blood test can be drawn alongside it. If you want cortisol in a broader picture, the Mito Core panel includes it with thyroid markers, inflammatory markers, and metabolic markers, with results reviewed by a clinician. Membership is optional. Order any test or panel at its listed price, or join for $9 a month or $99 a year for member pricing.

Your Next Move

Low cortisol is more than tiredness. It is a hormone deficiency that affects energy, blood pressure, blood sugar, and how well the body copes with illness or injury. The symptoms are real, the diagnosis is specific, and missing it can be dangerous.

If you have long-lasting fatigue, weakness, weight loss, dizziness on standing, or salt cravings, start with a morning cortisol and ACTH, and talk with a clinician about whether you need an ACTH stimulation test.

Frequently Asked Questions

What are the early warning signs of low cortisol levels?

Early signs often include fatigue that does not improve with rest, muscle weakness, loss of appetite, weight loss, dizziness when standing, and salt cravings. These symptoms come on slowly and overlap with many other conditions, so a morning cortisol test, followed by stimulation testing when needed, is the way to know [9][10].

What causes low cortisol in females?

The causes are the same in women and men, but some matter more for women. Addison’s disease, most often autoimmune, is more common in women than in men and occurs most often between ages 30 and 50 [11]. Sheehan syndrome, pituitary damage after severe bleeding during or after childbirth, is a cause seen only in women [8]. Stopping long-term steroids, often prescribed for conditions such as asthma, rheumatoid arthritis, and lupus, is the most common cause overall [9][11]. In women, low cortisol can also show up as irregular or missed periods and low sex drive [9]. The Endocrine Society advises testing pregnant women who have unexplained persistent nausea, fatigue, and low blood pressure [4].

What does a cortisol crash feel like?

“Cortisol crash” is not a medical term. People often use it for an afternoon energy slump, which is normal because cortisol falls through the day. A true drop in cortisol from adrenal insufficiency feels like the symptoms above: lasting fatigue, weakness, poor appetite, nausea, and dizziness on standing. A sudden, severe drop, called adrenal crisis, brings severe pain in the lower back, abdomen, or legs, vomiting, confusion, or fainting, and needs emergency care [9][11].

What is the difference between primary and secondary adrenal insufficiency?

In primary adrenal insufficiency (Addison’s disease), the adrenal glands themselves are damaged, most often by autoimmune destruction of the adrenal cortex. This can affect production of cortisol, aldosterone, and adrenal androgens. Secondary adrenal insufficiency occurs when the adrenal glands are intact but receive insufficient stimulation from the pituitary gland, which produces ACTH. The distinction matters because primary insufficiency may cause unique symptoms like skin darkening and salt cravings due to aldosterone deficiency, while secondary insufficiency typically does not [3][4].

Why does low cortisol cause fatigue even after sleeping enough?

Cortisol helps the liver make glucose and keeps blood pressure stable, so too little of it leaves less fuel available and can cause weakness and lightheadedness. Cortisol also normally peaks in the early morning. When the adrenal glands cannot make enough, more sleep does not replace the missing hormone [1][11].

Can low cortisol cause inflammation or autoimmune flare-ups?

Cortisol is the body’s main natural anti-inflammatory hormone, but the clearer link runs the other way: autoimmune Addison’s disease often occurs alongside other autoimmune conditions, particularly autoimmune thyroid disease, so people with it are screened for them [4]. Having another autoimmune condition along with persistent fatigue, weight loss, or dizziness on standing is a reason to consider cortisol testing.

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Resources

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