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Nutrition Consultations with Val Cortisol Awakening ResponseZRT Lab processes your order completely from beginning to end.

  1. The test kit is sent directly to you along with instructions.
  2. You send completed kit and forms back to ZRT (all shipping is paid).
  3. ZRT will email your results directly to you alone.

The results are clear but should you need help interpreting your test you can schedule an appointment for a consultation. Please click below to contact Valerie Robitaille, MS, PhD(c), Holistic Nutritionist

Cortisol Awakening Response

The Cortisol Awakening Response – also called CAR – reveals more detailed clues that help in assessing adrenal hormone/HPA Axis dysfunction. This testing is often useful for cases of PTSD, major depression, chronic fatigue syndrome and other severe stress conditions.


To help you decide which hormone test is right for you, download our Symptoms Checklist:

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Dr. David Zava, ZRT Labs


Additional Information

Diurnal Cortisol Curve Assessment

Thirty minutes after awakening from a good night’s sleep, cortisol levels are at the highest they’ll be all day. Following the morning peak, cortisol levels then fall to less than half that peak level by noon. They continue to drop to very low levels at night where they stay low during the sleep hours. Some individuals have a sharp rise to reach morning levels, others a more gradual incline. Looking at cortisol levels graphed during the day, any abnormal elevation, or depression of levels, or a loss of the expected curve with its characteristic morning peak and swooping decline towards evening may suggest HPA (hypothalamus-pituitary-adrenal) axis dysfunction – which is what we’re most interested in assessing when we’re looking at a diurnal cortisol curve.

Diurnal Cortisol Curves

This curve is derived from taking four daily saliva collections – typically done upon waking, before lunch, before dinner and before bed – and charting them on a 24-hour graph.

The resulting curve – also called a four-point cortisol curve or circadian cortisol pattern – reveals cortisol levels throughout the day, allowing the pinpointing of  issues with adrenal gland function.

adrenal curve normal Cortisol Awakening Response



This pattern shows a normal rise in cortisol production within 30 minutes of waking for the day. Cortisol levels then drop throughout the day, reaching their lowest point at bedtime.





Diurnal Cortisol Patterns with Adrenal HPA Axis Dysfunction

Cortisol production is normally at its highest 30 minutes after waking and declines steadily during the day, reaching its lowest point at bedtime. Those with adrenal gland dysfunction generally have irregularities in their diurnal cortisol curves. Some common examples are shown below.

adrenal curve chronic stress Cortisol Awakening Response




Overall higher than normal cortisol production throughout the day can result from prolonged stress demands. General symptoms include feeling “tired but wired,” food cravings, insomnia and anxiety.





adrenal curve stress fatigue Cortisol Awakening Response




The pattern for chronic fatigue shows an elevated morning cortisol with levels dropping off rapidly during the day. General symptoms include mid-day energy drop, drowsiness and poor exercise recovery.





adrenal curve burnout Cortisol Awakening Response




The burnout pattern, also commonly called “adrenal fatigue” is really a reflection of low overall cortisol during the day. General symptoms include day-long fatigue, irritability, food cravings, insomnia and exhaustion.





The Cortisol Awakening Response

Sunlight influences the diurnal rhythm and when it becomes scarce, those rhythms can become dysregulated. The adrenal hormone, cortisol, reacts to stressors in the body like inflammation, illness and low blood sugar; however, outside of its first-response job, it follows a very typical diurnal rhythm. It can be measured upon waking and throughout the day with results in saliva that look a lot like the graph below.

saliva cortisol Cortisol Awakening Response

Normally, in the morning as the sun begins its ascent, cortisol charts its course toward the highest level of our 24-hour day. Within 30 minutes of waking up, cortisol should continue to rise by about 50% from the waking level. When the mornings are dark, in susceptible individuals the diurnal rhythm of cortisol flattens out and it becomes difficult to shake off sleep and function normally. Another helpful measure of the HPA axis that captures that 50% rise (or absence of it) is called the cortisol awakening response (CAR) which measures cortisol in response to the “stress” of waking.



Here’s a normal CAR — observe the 2nd black dot in the graph below showing the cortisol level at 30 minutes after the initial waking sample:

saliva cortisol 2 Cortisol Awakening Response






Here’s an example of a CAR in someone struggling with SAD:

saliva cortisol 3 Cortisol Awakening Response



Notice the morning, noon, evening and night cortisol levels are roughly within normal ranges while the attenuated CAR is the finding of interest. Overall, the defect in cortisol regulation in SAD may be missed if the CAR isn’t assessed along with the diurnal rhythm.

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