Can I test my own cortisol at home? What tests are worth it?

The most clinically informative cortisol test for investigating diurnal rhythm dysregulation is the 4-point salivary cortisol test (samples collected at waking, noon, afternoon, and evening), which profiles the full diurnal curve and identifies whether the problem is blunted CAR, elevated evening cortisol, or a flat overall pattern, available through your physician or through CLIA-certified mail-order tests (DUTCH Complete, Genova Diagnostics) at $150–$350 (Aardal & Holm, J Clin Chem Clin Biochem, 1995).

A one-time blood cortisol test in a physician's office is largely uninformative for diurnal rhythm assessment, it only tells you cortisol at one point in time, typically in the morning after you have already experienced clinic-visit-induced stress. Salivary cortisol is biologically active (free) cortisol only, not total cortisol (which includes protein-bound, inactive cortisol measured in blood), making saliva the preferred medium for rhythm assessment. The DUTCH urine test additionally measures cortisol metabolites (particularly cortisone) and provides information about how your body is metabolizing cortisol, not just producing it.

Honesty Scale: Solid (1) for 4-point salivary cortisol as the appropriate test for diurnal rhythm assessment.

What to do: If you want to investigate your cortisol rhythm, request a 4-point saliva test through your physician, or order DUTCH Complete independently. On test day: collect all samples at the specified times, avoid physical exertion, caffeine, and food 30 minutes before collection. Bring results to a physician who is familiar with interpreting diurnal cortisol patterns, not all primary care physicians have this literacy.

For the full picture, read The Cortisol Rhythm Deep Dive