Skip to content

Cortisol (serum/plasma, measured at 9 PM)

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

This test measures your cortisol hormone level in your blood taken at 9 PM to help assess how your body responds to stress or certain medical conditions.

Quick summary

["Understanding your evening cortisol levels can help identify stress-related or hormonal imbalances."]

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

Key facts at a glance

LOINC
50432-4
Short code
Cortis 9 PM SerPl-mCnc
Synonyms
Cortis 9 PM SerPl-mCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
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 This Test Is Done

Doctors may order this test if they suspect conditions like Cushing’s syndrome, adrenal insufficiency, or other stress-related disorders. It can also be used to evaluate how your body’s cortisol levels fluctuate naturally over time.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if blood is drawn in the morning. If your blood is drawn at 9 PM, you may eat a light meal beforehand to avoid discomfort.

What the Test Involves

A healthcare provider will draw blood from a vein in your arm. The blood sample will be sent to a lab to measure cortisol concentration at the specified time.

What the Results Mean

Results help determine if your cortisol levels are too high or too low at night, which can indicate underlying health issues. Your doctor will interpret the results in the context of your medical history and other tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Nighttime Cortisol Level

Frequently asked questions

How is cortisol measured?
Cortisol is measured using a blood sample taken at 9 PM, typically via a simple venipuncture. The lab uses a sensitive immunoassay method to detect cortisol concentration in your serum or plasma.
What does a low cortisol level at night mean?
A low cortisol level at night may suggest adrenal insufficiency or an issue with your pituitary gland, which regulates cortisol production. Your doctor may recommend further testing or treatment to address the cause.
Can I take medication before this test?
Yes, you should follow your doctor’s instructions regarding any medications to take or avoid before the test. Some medications may affect cortisol levels, so it’s important to discuss this with your healthcare provider.
  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