Cortisol
The cortisol blood test measures levels of the body’s main stress hormone. It helps assess adrenal function and the body’s response to physical and emotional stress.
Turnaround time
1 day
Biomarkers count
1
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Details about Cortisol
What is the Cortisol test?
The Cortisol test measures the concentration of cortisol in the blood. Cortisol is a steroid hormone produced by the adrenal glands and plays a vital role in regulating metabolism, blood pressure, immune response, and the body’s stress reaction.
Cortisol follows a diurnal rhythm, meaning levels are normally highest in the early morning and lowest at night. Because of this natural variation, the timing of the test is important and is usually performed in the morning unless otherwise specified.
This test is commonly used in endocrinology to investigate adrenal gland function and disorders related to cortisol imbalance.
Why do I need a Cortisol test?
Abnormal cortisol levels can affect multiple systems in the body and may contribute to fatigue, metabolic changes, mood disturbances, and blood pressure issues.
Testing cortisol helps identify whether symptoms are related to excess or insufficient cortisol production.
You may need a Cortisol test if you experience:
- Persistent fatigue or weakness
- Chronic stress or burnout symptoms
- Unexplained weight gain or weight loss
- Low or high blood pressure
- Sleep disturbances
- Anxiety, low mood, or irritability
- Muscle weakness
- Changes in blood sugar levels
Conditions commonly associated with abnormal cortisol levels include:
- Adrenal insufficiency
- Cushing’s syndrome
- Chronic stress-related disorders
Benefits of the Cortisol test
- Assesses adrenal gland function
Evaluates cortisol production capacity. - Supports investigation of chronic fatigue
Helps identify hormonal causes. - Identifies cortisol excess or deficiency
Guides further endocrine testing. - Supports diagnosis of adrenal disorders
Used in standard endocrine practice. - Provides insight into stress response
Reflects physiological stress load. - Simple and widely used blood test
Requires only a single sample. - Supports treatment planning
Guides further investigation or referral. - Clinically recognised hormone marker
Used in NHS and private settings.
Step by step – how the test works
You can access Cortisol testing UK-wide through two options:
- Clinic appointment
Choose your nearest UK clinic. A healthcare professional will take your blood sample, usually in the morning. - At-home or hotel visit (£60 extra)
A qualified phlebotomist visits your home or hotel, so you don’t need to travel.
Your sample is analysed in an accredited UK laboratory, and results are delivered securely.
Your results explained
Low cortisol levels
May indicate reduced adrenal function or adrenal insufficiency and can be associated with fatigue, low blood pressure, and weakness.
Typical UK reference range (morning):
- < 140 nmol/L
Normal cortisol levels
Suggest normal adrenal hormone production and stress response.
Typical UK reference range (morning):
- 140–690 nmol/L
High cortisol levels
May indicate excessive cortisol production, often associated with prolonged stress or endocrine disorders.
Typical UK reference range (morning):
- > 690 nmol/L
Reference ranges vary by laboratory and time of sample collection.
How It Works
Simple steps to get your results
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Choose your test online and book in seconds. Select your preferred clinic location or home visit option.
Visit or Test at Home
Attend one of our UK or London clinics, arrange a home nurse visit, or use a finger-prick kit where available.
Get Your Results
Your sample is analysed by accredited UK laboratories, with secure results delivered directly to you.
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WhatsApp UsHow to Prepare for Your Test
Follow these guidelines for accurate results
Sample Timing
Where possible, attend your blood test between 7am and 12pm. Please wait until any short-term illness or infection has fully resolved before testing. Avoid intense exercise for 24–48 hours beforehand, as this can affect certain markers.
Fasting & Hydration
Fasting is not always required, but some tests may recommend it. If fasting is advised, avoid food for 8–12 hours before your appointment and drink water only. Stay well hydrated, as this helps with sample collection and accuracy.
Medications & Supplements
Continue prescribed medications unless advised otherwise by your clinician. Avoid vitamin, mineral, or biotin supplements for at least 24–48 hours before your test, as these can interfere with results. If you are unsure about any medication or supplement, please let us know before your appointment.
Hormones & Menstrual Cycle
For hormone-related tests, timing within your menstrual cycle may be important. If relevant, follow any specific guidance provided on your test page.
If you have any questions or special circumstances, our team is happy to advise before your appointment.