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Cortisol (Serum or Plasma Concentration)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of cortisol, a natural steroid hormone produced by your adrenal glands. It helps assess adrenal function and hormone balance.

Quick summary

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

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
73343-6
Short code
Hydrocortisone ind plt IgM SerPl Ql FC
Synonyms
Hydrocortisone ind plt IgM SerPl Ql FC
Category
hematology
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
CPT
82784
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 adrenal insufficiency (Addison’s disease), Cushing’s syndrome, or to evaluate stress-related hormone imbalances. It can also help check for pituitary issues that affect cortisol production.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where cortisol levels are measured using a sensitive immunoassay method. Results are compared to standard reference ranges to determine your hormone levels.

What Are Common Uses?

Cortisol testing is often used in combination with other tests, such as a 24-hour urine cortisol collection or an ACTH stimulation test, to provide a clearer picture of your adrenal gland function and overall hormone health.

What Might Affect Results?

Several factors can influence cortisol levels, including time of day (cortisol peaks in the morning), stress, medications (like steroids), recent illness, or even recent physical activity. If you’re taking medications or have recent health changes, let your doctor know.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low cortisol levels may indicate adrenal gland problems, such as insufficient production due to autoimmune disease, infection, or long-term steroid use. High cortisol levels could signal overproduction from conditions like Cushing’s syndrome or prolonged stress. Early detection helps guide treatment plans, such as hormone replacement or managing stress triggers.

Short name

Cortisol Level

Frequently asked questions

What does a cortisol test tell me about my health?
It provides a snapshot of your cortisol levels, helping identify whether your adrenal glands are functioning normally or if there’s an imbalance that may require medical attention.
Can cortisol levels change based on when I have the test?
Yes, cortisol levels naturally rise in the morning and fall later in the day. If your test is for a specific time-sensitive condition, your doctor may recommend testing at a particular time or using a 24-hour urine test for more accurate results.
Do I need to prepare for this test?
Generally, no special preparation is needed, but avoid heavy meals or excessive caffeine before the test. If you’re on medications that affect cortisol, like steroids, discuss this with your doctor before the test.
  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 16, 2026. · Read our editorial policy