Skip to content

Cortisol, Plasma or Serum, Substance Concentration

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

This test measures the amount of cortisol, a hormone produced by your adrenal glands, in your blood. Cortisol helps regulate metabolism, immune response, and stress reactions.

Quick summary

["Cortisol helps manage stress and supports normal bodily functions, and this test helps doctors assess adrenal health or hormone imbalances."]

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

Key facts at a glance

LOINC
83090-1
Short code
Cortis SerPl IA-sCnc
Synonyms
Cortis SerPl IA-sCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 check for problems with cortisol production or metabolism. It can also be used before certain surgeries or during pregnancy to evaluate adrenal function.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if timing your cortisol levels around a specific time of day (morning or evening) is important. Bring any medications you’re taking to your appointment.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but the process usually takes a few minutes. The blood sample is then sent to a lab for analysis.

What Are Possible Results?

Results are compared to general reference ranges for cortisol concentration in plasma or serum. Low or high levels may signal underlying health concerns that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Cortisol is crucial for managing stress, immune function, and metabolism. Abnormally low cortisol (adrenal insufficiency) can cause fatigue, weight loss, or dizziness, while high cortisol (Cushing’s syndrome) may lead to weight gain, high blood pressure, or muscle weakness. Your doctor will interpret results in the context of your symptoms and medical history.

Short name

Cortisol Level

Frequently asked questions

What causes cortisol levels to be tested?
Cortisol testing is often done if you have symptoms like unexplained fatigue, weight changes, or signs of hormonal imbalances. It may also be part of a diagnostic workup for conditions like adrenal disorders, Cushing’s syndrome, or to check for issues before certain treatments.
How is cortisol tested?
Blood is drawn from a vein, usually in the morning or evening depending on the test’s purpose. The sample is analyzed in a lab to measure cortisol concentration in your blood plasma or serum.
Can cortisol levels change based on time of day?
Yes, cortisol levels naturally rise and fall throughout the day, peaking in the morning and dropping at night. Some tests may require blood to be drawn at specific times (e.g., morning or evening) for accurate results.
  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