What is cortisol?

Cortisol is a glucocorticoid hormone produced by the adrenal glands. It follows a circadian rhythm, peaking in the morning to help with waking, then declining across the day. It regulates many systems including energy allocation, metabolism, inflammation control and the stress response.

Why does it matter for long-term health and wellbeing?

Because cortisol interfaces with energy balance, appetite, inflammation, and recovery systems, persistent dysregulation—whether too high or too low—can gradually undermine metabolic health, sleep quality, emotional balance, and resilience. Tracking trends through a saliva cortisol test gives insight into how well your body is adapting to life stress, lifestyle load, and recovery over time.

What’s an optimal level of cortisol?

What influences cortisol levels?

Key factors include sleep timing and quality, stress exposure (mental or physical), circadian rhythm entrainment, diet (especially carbohydrate and caffeine patterns), exercise timing and intensity, light exposure (morning bright light in particular), and recovery habits (rest, relaxation, downtime). Environmental and seasonal factors can also shift cortisol patterns (for example, sunrise timing shifts and seasonal variation in cortisol have been observed in Australian populations).

What does it mean if cortisol is outside the optimal range?

• Above optimal / high side: may suggest your body is under chronic load or in a heightened stress state — potentially pushing metabolic systems, appetite regulation and sleep into imbalance.
• Below optimal / low side: may indicate a system under strain or exhaustion, with reduced capacity to respond adaptively to daily challenges.

Either way, an out-of-range result is not a diagnosis but a signal — a launch point for deeper insight and lifestyle tuning (and discussion with your clinician, if needed).

How can I support healthy cortisol levels?

You can help your cortisol balance by: keeping a consistent sleep–wake schedule, prioritising morning bright light (natural daylight), moderating caffeine or stimulants (especially later in the day), using stress-modulating practices (e.g. mindfulness, breathing, gentle movement), spacing exercise appropriately, ensuring periods of recovery and rest, optimising nutrition (balanced macronutrients, stabilised blood sugar), and avoiding overtraining or excessive load without recovery. Tracking over time helps you see which levers move your cortisol in the right direction.

This information is provided for general health and wellness purposes only and does not replace medical advice.

References

1. Royal College of Pathologists of Australasia. (2024). Cortisol – RCPA Manual.
2. Hadlow, N., Brown, S., Wardrop, R., & Henley, D. (2014). The effects of season, daylight saving and time of sunrise on serum cortisol in a large population. Chronobiology International, 31(2), 243–251.
3. Hadlow, N., et al. (2018). Where in the world? Latitude, longitude and season contribute to the complex coordinates determining cortisol levels. Clinical Endocrinology (Australia populations)
4. Austin Pathology. (2024). Clinical Trials / Reference Ranges. (6am–10am cortisol: 185–624 nmol/L)