What is the cortisol awakening response, and should I have one?

The cortisol awakening response (CAR) is a 50–160% surge in cortisol levels occurring within the first 30–45 minutes after waking, it is a healthy, evolutionarily programmed response that mobilizes blood sugar, activates the immune system, and drives morning alertness, and a blunted or absent CAR (not elevated CAR) is the pathological pattern associated with burnout, adrenal fatigue, and chronic HPA axis suppression in high-achieving men (Clow et al., Neurosci Biobehav Rev, 2010).

This is one of the most commonly misunderstood concepts in the consumer health space. Men who feel exhausted in the morning and dread starting their day are often told they have "high cortisol", when in fact they have low or absent CAR. The morning cortisol surge is what makes you want to get up, feel alert, and engage with the day. When that surge is blunted, because the HPA axis is chronically suppressed by sustained stress, poor sleep, or burnout, mornings feel catastrophically difficult. The man who cannot get going without three coffees and still feels foggy until noon often has a blunted CAR, not a cortisol excess problem.

Honesty Scale: Solid (1). CAR biology and its association with burnout/HPA suppression is established in neuroendocrinology research.

What to do: If you suspect a blunted CAR, a 4-point salivary cortisol test (saliva collected within 30 minutes of waking, at noon, at 4 PM, and at 8 PM) profiles your full diurnal curve and identifies whether your CAR is blunted, normal, or elevated. Order through your physician or a CLIA-certified mail-order test such as DUTCH or Genova Diagnostics.

For the full picture, read The Cortisol Rhythm Deep Dive