23/09/2026
What's the best test for measuring cortisol?
A single blood test for cortisol can be useful for diagnosing (or ruling out) acute adrenal conditions such as Cushing's syndrome or Addison's disease.
But for understanding symptoms like fatigue, mood changes, brain fog and PMS where stress is a possible root cause, then a saliva and urine test collected across the day is a better alternative.
A comprehensive urine and saliva test can provide valuable additional information on:
1) Your cortisol awakening response (CAR): cortisol should rise by 50% or more after waking. A flat CAR can indicate burnout and even autoimmune conditions. A sharp CAR can indicate high anticipatory stress.
2) Daily cortisol pattern: how your cortisol changes across the day provided additional insights into your circadian rhythm. For example, high bedtime cortisol correlates with feeling 'wired but tired'.
3) Metabolised cortisol: this shows how much cortisol you actually make during the day and how much you break down. Low metabolised cortisol correlates strongly with hypothyroidism.
4) Cortisone: the inactive form. Your body can deactivate cortisol to cortisone in times of prolonged stress.
Our Advanced Hormone Test assesses all of these markers alongside reproductive hormones like estrogen, progesterone and testosterone.
Got questions about cortisol? Pop them below.
