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Cortisol, Serum (11 PM)

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

This test measures your cortisol hormone level in your blood at 11 PM to help assess your body’s stress response and adrenal function.

Quick summary

["Understanding your cortisol levels at night can help identify issues with stress regulation or adrenal health."]

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

Key facts at a glance

LOINC
21222-5
Short code
Cortis 11 PM SerPl-mCnc
Synonyms
Cortis 11 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 Is This Test Done?

Your doctor may order this test if you have symptoms like fatigue, weight changes, or unexplained stress, or if they suspect conditions like Cushing’s syndrome, adrenal insufficiency, or circadian rhythm disorders.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring your test results from previous cortisol tests if applicable.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The sample will be sent to a lab for analysis of cortisol concentration.

What Are the Results Meaning?

Results help evaluate whether your cortisol levels are too high or too low at night, which can indicate problems with stress management or hormonal balance.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Nighttime Cortisol Level

Frequently asked questions

What does a low cortisol level at night mean?
A low cortisol level at night may indicate adrenal insufficiency, where your body struggles to produce enough cortisol to regulate stress responses properly. It could also be linked to conditions like Addison’s disease or certain medications that affect hormone production.
What if my cortisol level is high at night?
High cortisol at night might suggest chronic stress, Cushing’s syndrome (excess cortisol from the adrenal glands), or other conditions that disrupt normal hormone timing. Your doctor may recommend further testing to determine the cause.
Can diet or lifestyle affect this test?
Yes, certain foods, medications (like steroids), caffeine, or alcohol can influence cortisol levels. Avoiding these before the test may improve accuracy, but always follow your doctor’s specific instructions.
  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