Persistent stress reshapes your biochemistry. Cortisol, the main stress hormone produced by your adrenal glands, is the most directly measurable signal of how your body is responding. A morning cortisol blood test, taken between 8am and 9am when levels naturally peak, is the standard UK starting point for investigating chronic stress, burnout or unexplained fatigue.
What cortisol actually does
Cortisol follows a daily rhythm: it peaks in the morning to wake you up, falls through the day, and reaches its low point around midnight. Short-term spikes in response to stress or low blood sugar are healthy and necessary. The problem is when cortisol stays elevated over weeks and months: it drives central weight gain, insulin resistance, suppressed immunity, poor sleep, anxiety and the classic 'tired but wired' pattern that defines burnout.
Signs cortisol might be a factor
Waking at 3 or 4am unable to get back to sleep. Stubborn fat around the abdomen and face. Persistent sugar or salt cravings. Easy bruising or skin that does not heal well. Mood swings or low-grade anxiety that does not match your circumstances. These are not diagnostic on their own, but together they justify a measurement.
How testing works
The standard UK test is a morning blood cortisol between 8am and 9am, fasting, with no recent exercise or caffeine. The result tells you where you sit on the typical reference range. For a fuller picture of daily rhythm, salivary cortisol at four points across the day is sometimes used, but blood cortisol is the first-line test. Chxhealth is a biomarker and genetic data provider. We do not diagnose, treat or prescribe. Our service supports your wellbeing journey alongside your healthcare professional.
What to do with the result
If cortisol is low or high, the next step is conversation with a clinician, not self-treatment. Lifestyle levers that lower cortisol over weeks: consistent sleep, regular meals (cortisol rises with skipped meals), strength training rather than long endurance sessions, breathwork and time in nature, and reduced caffeine and alcohol.
Chxhealth panels for this
Related biomarker guides
Frequently asked questions
When should I test cortisol?
Between 8am and 9am, after a 12 hour fast, before caffeine or exercise. Cortisol naturally peaks in the morning. Afternoon readings are not directly comparable.
Can low cortisol be a problem?
Yes. Persistently low cortisol can indicate adrenal insufficiency, which needs clinical assessment. Your report flags any out-of-range result. Chxhealth is a biomarker and genetic data provider. We do not diagnose, treat or prescribe. Our service supports your wellbeing journey alongside your healthcare professional.
About this article. Educational content. Chxhealth is a biomarker and genetic data provider. We do not diagnose, treat or prescribe. Our service supports your wellbeing journey alongside your healthcare professional. For medical advice about your health or results, please speak to a qualified clinician.