What is a hair cortisol test?

Hair cortisol testing is a method used to measure your long-term cortisol levels over several months. Based on decades of peer-reviewed research and used by scientists at leading universities worldwide — including the University of Oxford, Harvard, and King's College London — it provides a precise, averaged measure of cortisol exposure over time.

Unlike blood, saliva, and urine cortisol tests, which only capture a short-term snapshot, hair cortisol testing provides unique long-term insights into chronic stress, adrenal health, and longevity.

Different types of cortisol test

There are several types of cortisol test, each measuring a different window of time. Understanding the difference is important before choosing which one is right for you.

Blood, saliva and urine tests

These are short-term or 'acute' cortisol tests. They provide an indication of cortisol levels over minutes to hours. Because cortisol fluctuates minute-to-minute and day-to-day — influenced heavily by the time of day, stress levels, exercise, and medication — these tests can't tell you whether a high or low result is representative of your typical levels or just the circumstances of that particular morning.

Hair cortisol testing

Hair cortisol testing works differently. As hair grows at roughly 1cm per month, cortisol from the bloodstream is incorporated into the hair shaft. Analysing the segment of hair closest to the scalp gives a reliable, averaged picture of cortisol exposure over the preceding three months — unaffected by what happened on the day the sample was taken.

The key differences:

• Long-term measurement: Provides a multi-month view of cortisol trends, unlike blood, saliva and urine tests that only offer momentary snapshots.
• Chronic stress detection: Captures the sustained patterns that short-term testing misses due to natural daily variability.
• Accuracy: Less affected by acute stress, exercise, medication, or time of day — giving a more stable, reliable result.
• Non-invasive: A small hair sample collected at home. No needles, no clinic visits.

What can a hair cortisol test tell you?

A hair cortisol test can indicate chronic stress, help investigate adrenal disorders such as Addison's disease or Cushing's syndrome, and offer early warning signs of future health risks, including:

• Cardiovascular disease and heart attack risk
• Type 2 diabetes
• Stroke
• Fertility issues and IVF outcomes
• Alzheimer's and cognitive decline

Cortigenix's test provides insights across six key health areas: stress, immunity, fertility, brain health, longevity, and weight management.

How does Cortigenix's test work?

You order the kit online, collect a small hair sample from the back of your head at home (minimum 1cm, about 8–10 strands), and post it back using the prepaid envelope provided. Results appear in your secure personal dashboard within 10 working days.

No clinic visit. No needles. No need to time your sample for a specific time of day.

The science behind it

Hair cortisol testing has been studied and validated in thousands of research participants. It is used by scientists at the University of Oxford, King's College London, Harvard University, the University of Nottingham, and the University of Auckland, among others.

Peer-reviewed research has linked elevated hair cortisol levels to heart disease, stroke, metabolic disorders, impaired fertility, and accelerated ageing — with the 3-month average providing a far more meaningful risk indicator than any single blood test reading.

Read more: Hair cortisol test vs blood test — what's the difference?