Cortisol Test
Your body's primary stress hormone — and how it's typically measured.
A cortisol test measures the level of cortisol — your body's primary stress hormone — in blood, saliva or urine. Private cortisol tests in the UK are available from CQC-regulated providers, with most clinical labs preferring a morning blood sample taken between 8 and 10am.
What it measures
Serum cortisol
Salivary cortisol
ACTH
Why it matters
- Cortisol follows a daily curve — highest in the morning, lowest around midnight.
- Persistently high or low levels can point to adrenal or pituitary conditions that need medical assessment.
- Single readings have limited value without timing context; clinician interpretation is essential.
How testing works
- Order a morning cortisol blood test or a multi-sample salivary kit.
- Collect according to instructions — timing matters more than for most tests.
- Results are typically returned in 2–4 working days with reference ranges.
Compare Cortisol Test prices in the UK
Side-by-side comparison of CQC-regulated providers and UKAS-accredited laboratories. Transparent pricing, typical turnaround times and sample methods.
Frequently asked questions
What is a normal morning cortisol level?
UK labs typically use a morning serum cortisol reference range of around 133–537 nmol/L, but this varies by lab and assay. Always read the range printed on your own report.
Should I test blood or saliva?
Blood is the standard for screening single-time-point cortisol. Salivary tests across the day are better for assessing rhythm and are often used in functional medicine.
Can high cortisol cause weight gain?
Sustained high cortisol is associated with central weight gain, but many other factors are involved. A test is a starting point, not a diagnosis.
Related guides
This guide is for general information only and does not constitute medical advice. Always discuss test results with a qualified clinician.