Hair Cortisol Test
About this test
ELISA — chronic-stress assessment 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
Six months of data from one sample. Hair captures continuous free-cortisol exposure — not a 24-hour snapshot — validated against saliva and urine as a reliable retrospective marker. Elevated levels associate with chronic stress, depression, major life stress and metabolic disorders. 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 the real baseline — the retrospective biomarker for chronic stress.
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’s healthy. When it stays activated for months, that’s chronic stress, with consequences in slowed wound healing, cognitive impairment, depression and metabolic dysfunction. Hair cortisol measures the cumulative output of this system over time — the number that correlates with disease risk.
What the research shows
Hair cortisol concentration (HCC) has been validated across more than two decades of published research, correlating with chronic-stress exposure and used in cohort studies of cardiovascular risk, depression, burnout and pediatric stress.
Depression & mood: hair cortisol is elevated in major depression versus controls; the picture is more nuanced for prolonged disorders — PTSD and very long-term depression often show lower hair cortisol, suggesting HPA-axis exhaustion (Lucia et al., Stress 2011; Herane, J Psychiatr Res 2015).
Major life stress: in young adults, hair cortisol serves as a retrospective biomarker of major life stresses — bereavement, job loss, relationship breakdown — that conventional blood tests would have missed weeks later (Karlén et al., BMC Clinical Pathology 2011).
Maternal-child stress: hair cortisol in mothers and their children correlates significantly, useful for prenatal and postpartum stress monitoring (Karlén et al., Pediatrics 2013). The Whitehall II study found women generally have lower hair cortisol than men, diabetes associates with higher levels, corticosteroids lower measured levels, and high BMI correlates with higher cortisol.
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. Very high readings can indicate Cushing syndrome and very low readings Addison disease — both require clinical evaluation.
Method & reference-scale notes
The cortisol assay uses 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.
- Assessing chronic stress rather than a single-moment snapshot.
- Monitoring depression, major life stress, burnout, anxiety symptoms and metabolic disorders.
- Prenatal and postpartum stress monitoring.
- Tracking stress-reduction interventions — therapy, lifestyle changes, supplements — over 3–6 months.
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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