Chapter 03Measurement

Three ways to measure cortisol

A single cortisol value says little. What matters is the shape of the daily curve, and all three measures are read from that same curve.

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Fig. 03 · One day of salivary cortisol
CORTISOL FIRST 30 MIN SHOWN ENLARGED WAKE+30 MINMIDDAYBEDTIME peak (D) night (N) 1 2 3
Healthy pattern: a sharp rise, a clear drop and a mid-range total.
Optimal03 · Measurement

Read the whole curve

This is one day of salivary cortisol, from waking to bedtime. What matters is its shape:

How sharply it rises on waking, how steadily it falls, and how much is produced in total.

1Cortisol awakening response

The steep climb in the first 30 minutes after waking. It shows how well the HPA axis can mobilise energy for the day.

Sharp rise · healthyBlunted · concerning

2Diurnal slope

The drop from the morning peak to the evening low (D − N). A steady decline lets you wind down and sleep.

Clear drop · healthyFlat · concerning

3Area under the curve

The whole shaded area: how much cortisol the body makes across the day. Too much or too little both matter.

Mid range · healthyVery high or low · concerning

When the curve flattens

A blunted rise, little drop across the day and a low total: each of the three measures now reads as concerning.

Switch between the healthy and flattened patterns with the toggle above the chart.