General
ACTH (Adrenal Hormone)
Lab test

ACTH (Adrenal Hormone)

Ordered alongside cortisol when adrenal insufficiency or cortisol excess is suspected, or when prior testing has shown abnormal cortisol levels that need further context. Morning testing is required for accurate results. Results reviewed by a General Medicine clinician.

Receive actionable insights and deep analysis—not just lab values– in as little as 48 hours

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Most insurance accepted

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Available nationwide

What is an ACTH Test?

The ACTH test measures adrenocorticotropic hormone — the signal the pituitary gland sends to the adrenal glands to produce cortisol. Testing ACTH alongside cortisol is essential for pinpointing where in the hormonal axis a problem is occurring: whether the adrenal glands themselves are failing, or whether the pituitary or hypothalamus is not sending the right signal.

Adrenal insufficiency diagnosis

Elevated ACTH with low cortisol points to primary adrenal insufficiency (Addison's disease) — the adrenal glands are not responding to the pituitary's signal. This combination guides appropriate hormone replacement and investigation for the underlying cause.

Pituitary and hypothalamic dysfunction

Low ACTH alongside low cortisol indicates a problem at the pituitary or hypothalamic level rather than the adrenal glands — a critical distinction that changes both the diagnosis and treatment approach entirely.

Cushing's syndrome evaluation

Elevated cortisol with inappropriate ACTH levels helps distinguish between ACTH-dependent Cushing's (pituitary or ectopic tumor) and ACTH-independent Cushing's (adrenal tumor) — directing the appropriate next steps in evaluation and management.

Complete insights in as little as 48 hours

1

Book your test

Instantly schedule at 2,000+ labs nationwide, at a time that works for you. Most visits take 15 minutes or less, with both walk-ins and appointments available.

2

Get results in 48 hours

Your results are delivered quickly—and reviewed by medical professionals. You’ll get clear explanations, robust health insights, and recommended next steps tailored to your health needs.

3

Take action with physician guidance

Choose to review your results and manage your plan with a General Medicine physician—or simply use the insights on your own.

4

Track progress over time

Repeat annually to see trends, improvements, and new emerging risks or book individual tests that focus on your set goals

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We help you understand your options, connect you to the right clinicians, manage prescriptions, coordinate any needed evaluations, and keep an eye on your overall health along the way. It’s comprehensive care that looks at the full picture — your goals, your history, your lifestyle — and makes it simple to move forward with confidence.

Your care plan
Clinician

What's included

Test type

Blood sample

Collection method

Venipuncture

Fasting

Not required

Results processing time

1 to 3 days

ACTH Level

Measures the amount of the adrenocorticotropic hormone in your blood, indicating pituitary-adrenal function.

Virtual visit with clinician

Ongoing support, always available.

You’ll be supported by experienced clinicians who care for a wide range of health needs, from everyday concerns to more complex conditions.

Our clinicians track your progress over time and adjust your care as needed. If medication is prescribed, we’ll manage dosing and monitor for side effects. If lab testing is recommended, we review results and refine your plan accordingly. You’re never left to navigate care on your own.

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Frequently asked questions

What does an ACTH test measure?

ACTH (adrenocorticotropic hormone) is produced by the pituitary gland and signals the adrenal glands to produce cortisol. Testing ACTH alongside cortisol helps distinguish between primary adrenal insufficiency (Addison's disease), secondary adrenal insufficiency from pituitary dysfunction, and Cushing's syndrome.

When during the day should ACTH be tested?

ACTH follows a diurnal rhythm — levels are highest in the early morning (6–8 AM) and lowest in the evening. Testing should be done in the morning for the most diagnostically useful result. The sample must be handled carefully, as ACTH degrades quickly.

Do I need to fast for this test?

Fasting is generally recommended for 8–12 hours before ACTH testing for the most reliable results, and the blood draw should ideally be done early in the morning.

What symptoms would prompt ACTH testing?

Unexplained fatigue, weight loss, low blood pressure, salt craving, and skin darkening may suggest adrenal insufficiency. Weight gain, a rounded face, stretch marks, and easy bruising may suggest cortisol excess (Cushing's). Both scenarios warrant ACTH and cortisol testing.

Why is ACTH tested alongside cortisol?

The combination tells you where the problem is. High ACTH with low cortisol points to primary adrenal failure (Addison's). Low ACTH with low cortisol points to the pituitary or hypothalamus as the source. Testing one without the other provides an incomplete picture.
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