ZRT Cortisol Testing
Cortisol is a hormone produced by your adrenal glands that helps regulate your body’s response to stress, energy use, and many other functions. Cortisol levels normally follow a daily pattern (highest in the morning and lower at night). Testing can help identify patterns that may be relevant when you’re experiencing fatigue, poor sleep, “wired-tired” feelings, or stress-related symptoms—along with a full medical evaluation.
Why cortisol rhythm matters
Cortisol typically follows a circadian (daily) rhythm. Saliva testing is commonly used to assess cortisol patterns, and late-night salivary cortisol is also used clinically as a screening test for Cushing syndrome.
- Cortisol can be measured in blood, urine, or saliva. MedlinePlus (NIH)
- Cortisol has a circadian rhythm; saliva can be used to reflect daily patterns. NIH/PMC
- Late-night salivary cortisol is a first-line screening test for Cushing syndrome. Endocrine Society
What is ZRT cortisol testing?
ZRT offers saliva-based cortisol collection that can be performed at home. A common approach is a four-sample (“diurnal”) collection taken across one day to chart a cortisol curve (for example: morning, midday, afternoon/evening, and bedtime). This helps visualize your cortisol rhythm over the day.
What this test can help explore
- Daily cortisol rhythm patterns (morning-to-night)
- Sleep disruption (trouble falling asleep or staying asleep)
- Fatigue patterns (especially “morning drag” or “wired at night”)
- Stress physiology and recovery support planning
- Guidance for lifestyle, sleep, and nutrition strategy
Important note
Cortisol testing is one piece of a bigger clinical picture. Symptoms can overlap with many conditions (thyroid imbalance, anemia, sleep disorders, medication effects, mood disorders, and more).
If there are concerns for endocrine disease (e.g., hypercortisolism/Cushing syndrome), the appropriate medical evaluation and confirmatory testing are essential.
How the collection works
For a diurnal cortisol curve, saliva samples are collected at multiple times across a single day. The resulting report can show whether cortisol levels appear elevated at night, blunted in the morning, or otherwise out of an expected rhythm—information your clinician can interpret in context.
Typical timing (example)
- Upon waking
- Before lunch
- Before dinner
- Before bed
Preparation tips (common)
- Follow the kit’s timing instructions carefully
- Avoid eating, drinking (except water), brushing teeth, or gum right before collection (per kit directions)
- List medications/supplements for your clinician—some can affect results
- Try to collect on a “typical” day for you
What results may be used for
Your clinician may use patterns in your cortisol curve to inform a personalized plan. This can include sleep optimization, stress-recovery strategies, nutrition planning, and—when appropriate—additional lab testing. If results suggest a need for medical endocrine evaluation, we’ll discuss next steps.
Frequently Asked Questions
Evidence-informed answers with references to trusted medical sources.
Request ZRT Cortisol Testing
Request testing below. This form is for non-urgent requests. If this is an emergency, call 911.
What to expect
We’ll review your symptoms and goals, confirm the right test strategy, and provide instructions for sample collection. After results return, we’ll review them with you and discuss next steps.
Prefer to schedule immediately? Use your appointment link or call the office.