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Cortisol (serum/plasma, mass concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of cortisol, a natural steroid hormone produced by your adrenal glands, in your blood.

Quick summary

["Cortisol helps regulate metabolism, immune response, and stress reactions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
26532-2
Short code
Cortis 48h p ACTH SerPl-mCnc
Synonyms
Cortis 48h p ACTH SerPl-mCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
60
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order cortisol testing to diagnose or monitor conditions like Cushing’s syndrome, adrenal insufficiency, or to evaluate stress-related hormone imbalances. It can also help assess whether medications affecting cortisol levels are working properly.

What to Expect Before the Test

No special preparation is needed, but if you’re taking medications that affect cortisol (like steroids), your doctor may ask you to stop them temporarily or adjust timing. Avoid caffeine or alcohol before testing, as they can influence results.

During the Test

A small blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab for analysis. The test typically takes 1–2 days to return results.

What the Results Mean

Results are compared to general reference ranges, but individual results can vary based on factors like time of day, stress levels, and medications. High cortisol may indicate overproduction (e.g., Cushing’s), while low levels could signal adrenal gland issues.

Reference range

NCBI: ACTH 10-60 pg/mLN/A

Specimen: serum

Typically collected in the morning (8-10 AM). Inform your provider if taking steroid medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Cortisol Level

Frequently asked questions

Why might my cortisol test be done at night?
Cortisol levels naturally peak in the early morning and decline during sleep. Some tests, including overnight samples, measure cortisol at specific times to better assess adrenal function. Your doctor will explain the timing if needed.
Could food or medications affect my cortisol test?
Certain foods (like high-sodium or caffeine-rich items) and medications (e.g., steroids, beta-blockers) can influence cortisol levels. Your doctor may provide specific instructions to ensure accurate results, such as fasting or timing around meals.
What if my cortisol levels are outside the normal range?
If results are abnormal, your doctor may recommend further testing (e.g., 24-hour urine cortisol, dexamethasone suppression tests) or additional evaluations to identify the underlying cause, such as hormonal imbalances or medical conditions.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy