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Hair Cortisol Test for Addison's Disease
Addison's disease — primary adrenal insufficiency — causes the adrenal glands to produce insufficient cortisol. Because early symptoms are non-specific and overlap with many other conditions, diagnosis is often significantly delayed.
Standard blood cortisol tests measure output at one moment and can miss the sustained deficiency pattern that characterises Addison's. A hair cortisol test provides a 3-month average, making it easier to identify a consistently low cortisol pattern rather than a single borderline reading.
No blood. No needles.
Quick, easy at-home collection
Free UK postage
Single sample — no repeats needed
Clinically proven with expert support
About this test
Sample method: Hair | Measurement window: 3 months
Cortigenix's Cortisol Over Time (COT) test measures average cortisol levels over the past three months. In adrenal insufficiency, this sustained low reading is more clinically informative than a point-in-time blood draw, which can vary depending on the time of day, recent physical stress, and whether the patient is in an early or established stage of the condition.
This test is valuable both for those investigating a possible Addison's diagnosis and for those already diagnosed who want to monitor their cortisol levels and assess the adequacy of their cortisol replacement therapy over time.
Please note: this test is a monitoring and investigative tool. If you are experiencing an adrenal crisis (severe abdominal pain, extreme weakness, vomiting, loss of consciousness), seek emergency medical attention immediately.
Signs and symptoms of low cortisol / Addison's disease
Addison's symptoms develop gradually and are often attributed to other causes. You may not have all of these:
- Severe, persistent fatigue
- Unexplained weight loss and reduced appetite
- Low blood pressure, particularly dizziness on standing
- Darkening of the skin (hyperpigmentation), especially in skin folds and on lips
- Salt craving
- Nausea, vomiting, or abdominal pain
- Low blood sugar
- Low mood or depression
- Muscle weakness or cramps
- Brain fog
- Headaches
- Increased thirst and frequent urination
- Irregular periods
- Low-grade fever
Who should take this test?
- You have symptoms consistent with Addison's disease or adrenal insufficiency
- You want to support further investigation before or alongside a GP referral
- You have been diagnosed with Addison's disease and want to monitor your cortisol levels at home
- You are taking cortisol replacement therapy and want to check your levels between clinical reviews
- You have a known autoimmune condition and want to monitor adrenal health proactively
- Your blood tests have returned borderline results but symptoms continue
Why hair testing gives a clearer picture
Blood, saliva and urine tests capture cortisol at a single moment. But cortisol fluctuates constantly — by the hour and by the day — meaning a result on a calm morning can look completely different to one taken during a stressful week. A single snapshot can lead to results that are misleading or missed altogether.
Hair cortisol testing works differently. As hair grows (~1cm per month), cortisol from your bloodstream is incorporated into the hair shaft. Analysing the section closest to the scalp gives a reliable, averaged picture of cortisol exposure over the past three months — unaffected by whether you had a bad night before the test, or exercised that morning.
It's the same principle as an HbA1c test for blood sugar: one measurement that reflects sustained exposure over time, not just today.
Hair vs other cortisol tests
Other cortisol tests only measure where your cortisol sits at a single moment. But cortisol changes minute by minute — which is why a one-off blood test can miss the full picture. Hair cortisol testing works like an HbA1c for blood sugar: it gives you a reliable average over three months, not just a snapshot of today.
| Feature | Hair test Cortigenix | Blood test | Saliva test | Urine test |
|---|---|---|---|---|
| Measures cortisol over 3 months | ✓ | ✗ | ✗ | ✗ |
| Single sample — no repeat testing needed | ✓ | ✗ | ✗ | ✗ |
| Unaffected by acute stress on test day | ✓ | ✗ | ✗ | ✗ |
| Detects chronic (long-term) cortisol patterns | ✓ | ✗ | ✗ | ✗ |
| No needles or clinic visit required | ✓ | ✗ | ✓ | ✓ |
| Suitable for at-home self-collection | ✓ | ✗ | ✓ | ✓ |
| Results unaffected by time of day | ✓ | ✗ | ✗ | ✗ |
| Validated by peer-reviewed research | ✓ | ✓ | ✓ | ✓ |
| Useful for diagnosing adrenal conditions | ✓ | ✓ | ✓ | ✗ |
After years of unexplained symptoms, I was eventually diagnosed with Addison's disease. This test was invaluable in helping me get further investigations and manage my condition. It's easy to use, and the results are reliable. I highly recommend it to anyone dealing with adrenal issues.
R Wilkins
Living with Addison's is challenging, but this test has been a game-changer for me. Being able to monitor my cortisol levels at home gives me peace of mind and empowers me to take control of my health. A must-have tool for anyone managing this condition.
D Woodhouse
How it works
No clinic visit. No needles. Everything by post, all from home.
Step 1
Order your test kit
Step 2
Take a small hair sample at home
Step 3
Post your sample using the prepaid envelope
Step 4
Receive results in your secure portal within 10 days
Sample: A small hair sample from the back of your head — minimum 1cm in length, about 8–10 strands thick. Full instructions included in your kit.
Still have questions?
What is cortisol?
Cortisol is a hormone often called the 'stress hormone' because of its role in helping the body respond to stress. It regulates a wide range of functions: immune response, metabolism, reproductive health, blood pressure, and brain function. Every cell in the body has cortisol receptors, which is why prolonged imbalance — whether too high or too low — can affect so many aspects of your health.
Why measure cortisol over 3 months rather than with a single blood test?
Cortisol fluctuates constantly — it varies by the hour and can spike significantly on a stressful day. A single blood, saliva or urine test only captures a snapshot of one moment, which means a 'high' or 'low' result could simply reflect the circumstances of that morning.
Measuring cortisol in hair provides a reliable average over the past 3 months, in the same way an HbA1c test measures average blood sugar over 3 months rather than a single glucose reading. This makes it far more useful for assessing chronic stress, adrenal health, and long-term cortisol patterns.
Why does this test use hair rather than blood, saliva or urine?
Hair is a stable, long-term record of cortisol exposure. As hair grows (roughly 1cm per month), cortisol from the bloodstream becomes incorporated into the hair shaft. Analysing the section closest to the scalp gives a precise, averaged view of cortisol levels over the preceding three months.
Blood, saliva and urine tests are affected by acute stress, time of day, exercise, and medication taken before the test. Hair cortisol is not — making it a more objective and reproducible measure of your true long-term cortisol status.
What is the science behind Cortigenix's test?
Hair cortisol testing is backed by decades of peer-reviewed research and is used by scientists at institutions including the University of Oxford, King's College London, Harvard University, and the University of Auckland. Our test has been independently validated using data from thousands of participants. Research partners include the University of Nottingham, University of Auckland, and King's College London.
Is your test available worldwide?
Yes. We ship to over 170 countries. UK orders include free postage. International shipping rates are calculated at checkout.
How much hair do I need to provide?
You need a small sample from your head — a minimum of 1cm in length and approximately 8–10 strands thick (around 2–3mm). Full instructions are included in your kit.
Where should I take my sample from?
We recommend taking your sample from the back of your head, near the cranial bone (the bump you can feel at the base of your skull). This area tends to give the cleanest, most consistent results and the sample is not visible once taken.
Will hair dye or treatments affect my results?
No. All hair samples are thoroughly washed before analysis to remove external contaminants, including dyes, bleach, conditioner, and styling products. Your results will not be affected.
How are my results delivered?
Results are delivered to your secure personal dashboard within 10 working days of your sample arriving at our laboratory. You'll receive an email notification when they're ready. If your results are outside the normal range, one of our cortisol experts will be available to discuss next steps.