Hair Cortisol Test
About this test
ELISA — stress-hormone tracking over a 2–3 month exposure window.
What this test can show
Hair cortisol offers a retrospective look at cumulative cortisol exposure — the body’s primary stress hormone — captured as it’s incorporated into the hair over weeks to months.
Sample type
Hair — head, proximal 3 cm
Months of data from one sample. Hair captures continuous free-cortisol exposure — not a 24-hour snapshot — studied against saliva and urine as a retrospective marker of cumulative cortisol exposure. It is also the simplest test we offer: a small clip from the back of the head — no needles, no fasting, no fingerstick.
Why hair, not blood or saliva
Cortisol levels swing dramatically across a single day — high in the morning, low at night, spiking with caffeine, exercise, even a tense email. A blood or saliva test captures that one moment; hair captures the cumulative average across months.
Blood, saliva and urine capture cortisol at the moment of collection — affected by time of day, acute stress, caffeine and sleep. They are useful for diurnal-rhythm assessment but need multiple samples to see patterns. Hair incorporates free cortisol as it grows, smoothing over daily variation to show a cumulative average — a retrospective research marker of cortisol exposure.
The science — cortisol is the output of the HPA axis
The hypothalamic-pituitary-adrenal (HPA) axis is the body’s central stress-response system. Stress doesn’t make cortisol directly — it triggers a cascade: the hypothalamus releases CRH, the pituitary releases ACTH, and the adrenal glands produce cortisol.
When the axis activates briefly — a deadline, an argument, a workout — it settles again afterwards. When it stays activated over long periods, that is what the literature describes as chronic stress. Hair cortisol measures the cumulative output of this system over time.
What the research shows
Hair cortisol concentration (HCC) has been studied across more than two decades of published research as a retrospective marker of cumulative cortisol exposure, and used in cohort studies of sustained stress and in pregnancy and paediatric research.
Sustained stress: published research has examined hair cortisol in relation to prolonged psychological stress; findings vary with the duration and nature of the stressor, and some long-duration studies report lower rather than higher levels (Lucia et al., Stress 2011; Herane, J Psychiatr Res 2015).
Major life stress: in young adults, hair cortisol has been described as a retrospective marker of major life stresses — bereavement, job loss, relationship breakdown — that a single blood test taken weeks later would not capture (Karlén et al., BMC Clinical Pathology 2011).
Maternal-child research: hair cortisol in mothers and their children has been reported to correlate, and has been used in prenatal and postpartum stress research (Karlén et al., Pediatrics 2013). The Whitehall II study reported that women generally had lower hair cortisol than men and that corticosteroid use lowered measured levels.
Interpreting the result
Hair cortisol concentration is reported in picograms per milligram (pg/mg) and placed on a four-band reference scale (Low, Normal, Elevated, High) developed by CanAlt research and supported by the literature. The result reflects average free-cortisol exposure over approximately the past 3–6 months, depending on the hair length analyzed, and is read observationally in the context of the whole person.
Method & reference-scale notes
The cortisol assay is an enzyme-linked immunosorbent assay (ELISA) using antibodies for cortisol following hair extraction; as with any antibody-based assay, cross-reactivity may occur — principally with prednisolone and prednisone, so readings may be elevated in patients taking these steroids. Because there is no universal regulatory procedure and results depend on the hair-washing protocol used prior to extraction, the reference ranges are specific to CanAlt’s methodology; direct numerical comparison to other labs may not be valid.
- Stress-hormone tracking over 3–6 months, rather than a single-moment snapshot.
- Prenatal and postpartum stress-hormone tracking.
- Comparing cortisol exposure over time, 3–6 months apart, for research and educational purposes.
How is this different from a saliva or blood cortisol test?
Saliva, blood and urine cortisol measure the level at the moment of collection, which fluctuates dramatically across a single day — so a single spot test is hard to interpret without multiple samples. Hair cortisol smooths all that variation into one cumulative reading covering up to 6 months. It complements spot tests rather than replacing them: spot tests are better for diurnal-rhythm assessment, hair is better for chronic stress.
Will hair dye, bleach or chemical treatments affect results?
Yes — research shows dyed hair tends to read lower for cortisol, likely because the chemical processes wash out some incorporated cortisol. If the patient regularly colours or bleaches their hair, factor this into interpretation. Untreated hair from new growth at the nape gives the most reliable reading.
What if the patient is taking corticosteroid medications?
Important: the assay antibodies can cross-react with prednisolone and prednisone, so readings may appear elevated with these steroids. The Whitehall II study also found corticosteroids generally lower hair cortisol. Either way, note any corticosteroid use when interpreting results.
How much hair is needed, and what if it’s short?
We recommend 1–1.5 inches of hair, capturing roughly 3–4 months of exposure (hair grows ~1 cm/month). If the hair is too short to clip, finger or toenail clippings can be substituted — they incorporate cortisol through a similar mechanism, though hair is the better-validated sample.
How often should it be retested?
Because hair cortisol reflects the average over the previous several months, wait at least 3 months between tests to see meaningful change. For tracking a stress-reduction intervention, 3–6 months later is when you’d expect to see results.
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