This test measures the level of adrenocorticotropic hormone (ACTH) in your blood. ACTH is a chemical messenger made by the pituitary gland in your brain that tells your adrenal glands (small glands above your kidneys) to produce a hormone called cortisol. Cortisol helps your body handle stress, control blood sugar, and maintain blood pressure. Doctors use the ACTH test to check if your pituitary or adrenal glands are working properly. This test can help find the cause of symptoms like tiredness, weight changes, or high blood pressure, and is important for diagnosing some hormone-related health problems.

What it Measures

The ACTH test checks how much adrenocorticotropic hormone is in your blood. Here is what this means in simple terms:

ACTH (Adrenocorticotropic Hormone):
This hormone is made by your pituitary gland. Its main job is to signal your adrenal glands to make cortisol.
Cortisol:
Cortisol is a hormone that plays an important part in managing stress, reducing inflammation, controlling how your body uses sugar (glucose), and keeping your blood pressure normal.
Feedback System:
Your body has a feedback system to keep hormone levels balanced:

When cortisol is low, the pituitary gland makes more ACTH so the adrenal glands produce more cortisol.
If cortisol is high, ACTH levels drop to slow down cortisol production.

What the Test Shows:

The test helps check if your pituitary gland is making the right amount of ACTH.
It also tells if your adrenal glands are responding as they should by making enough cortisol.
Sometimes, high or low ACTH levels point to conditions like Cushing’s disease, Addison’s disease, or pituitary/adrenal gland problems.

Doctors may order both ACTH and cortisol tests together to better understand how your hormones are working.

Why is it Important

Helps Diagnose Hormone Problems:
This test helps doctors find out if your symptoms (like weakness or sudden weight changes) are caused by issues with your adrenal or pituitary glands, which are important for making hormones your body needs.
Monitors Conditions:
If you have a known hormone disorder, such as Addison's disease or Cushing’s disease, regular ACTH testing helps your doctor see how well your treatment is working or if your condition has changed.
Guides Treatment:
If the ACTH level is too high or too low, it helps your doctor decide which medicines or next tests you may need for better hormone balance. This helps you get the right care faster.
Detects Tumors or Gland Issues:
Abnormal ACTH levels can signal growths (tumors) or damage in your adrenal glands or pituitary gland. Early detection is key for better health outcomes.
Supports Stress and Metabolism Management:
Understanding your ACTH and cortisol can explain problems with handling stress, low energy, or metabolism issues, leading to safer and more effective treatment plans.

When Should I Get This Test?

Your doctor may suggest this test if you have:

Unexplained tiredness or muscle weakness
Sudden weight loss or gain
Darkening of the skin (especially not exposed to sun)
High blood pressure or changes in blood sugar
Signs of hormone imbalance, like mood changes, thin skin, or stretch marks

You might also need it if you have ongoing concerns with hormone health, adrenal or pituitary gland disorders, or your doctor wants to check your response to certain treatments.

Interpretation of Test Results

Understanding what your results might mean is helpful, but always discuss them with a doctor for a proper diagnosis.

Result Type	What it Means
Normal	Your ACTH level is balanced; pituitary & adrenal glands working well
Borderline	Slight changes; may need further tests to find the root cause
Abnormal	ACTH too high or too low; may signal a problem with adrenal or pituitary glands, or a related condition

(Note: Specific normal ranges can vary slightly between labs and depending on individual factors. Always refer to the ranges provided on your report and consult your doctor.)

Additional Information

ACTH levels can change with stress, time of day, and certain medicines.
This test alone cannot diagnose a disease; it’s one part of a bigger health picture.
If your results are unusual, your doctor might order more tests, ask about your medicines, or review your symptoms to guide care. Always follow your doctor’s advice.

Test Requirements

Sample type: Blood (taken from a vein in your arm)
Fasting: Not required—you can eat and drink normally unless your doctor tells you otherwise.
Precautions: Tell your doctor about any medicines (especially steroids) you take, as some drugs affect the results. Arrive at the lab in the morning for best accuracy, unless advised differently.

Partnered Health Labs:

FAQs

Do I need to fast before the ACTH test?
No, fasting is not necessary for the ACTH blood test. You can eat and drink as you normally would unless your doctor gives special instructions. However, try to avoid taking any steroid medication unless your doctor says it’s okay, as this can affect your results.
What should I do if my results are abnormal?
Don’t panic. Abnormal levels do not always mean you have a disease. Talk to your doctor—more tests might be needed before making any diagnosis. Together, you can decide on the right next steps for your health.
Can pregnancy affect my test result?
Yes, pregnancy can naturally change your hormone levels, including ACTH. If you are pregnant or believe you might be, let your doctor know before the test; this helps them interpret your results correctly.
How do I understand if my levels are high or low?
High levels may mean your body is making too much ACTH, sometimes from pituitary gland problems. Low levels may suggest your adrenal or pituitary gland is not working well. These results always need a doctor’s interpretation since normal ranges vary.
What if I am taking steroid medicines?
Steroid medicines can lower your ACTH readings. It is important to tell your doctor about all your medicines before the test. Never stop any prescribed medicine without speaking to your physician first.

For more detailed information, see Netmeds Health Library blog: Cortisol: Structure, Crucial Functions, Adverse Effects.

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