Why we don't test for cortisol

We only include a test if it can give you accurate, consistent results that lead to actionable next steps. Cortisol testing has genuine value in certain clinical and research settings, but for everyday consumer health monitoring, the evidence tells a more complicated story.

The idea of testing cortisol to reveal your stress levels is appealing (and totally logical). And because the disrupted cortisol patterns caused by chronic stress are associated with poorer health, it makes sense that you’d want to measure it. 

But for the purpose of giving you actionable, reliable insights about their stress levels, cortisol testing has some significant limitations. We use other biomarkers instead, like HbA1c and lipid profiles, which show us the downstream effects of chronic stress with more consistency. These give us results we can confidently translate into practical guidance for you.

Keep reading to find out why cortisol isn’t in our standard consumer test range, and which tests we think give you better insights into your health.

Why cortisol testing is unreliable for monitoring stress

Cortisol isn’t inherently bad. It helps you react quickly in high-stakes situations while regulating blood pressure, metabolism, and insulin. Problems arise when your body treats modern stressors like genuine threats, keeping cortisol chronically elevated.

Your cortisol follows a 24-hour circadian rhythm, peaking shortly after waking and declining gradually through the day. Short-term stressors, like hitting bad traffic on your commute, can cause temporary spikes that dramatically increase cortisol. These spikes drop off quickly, but chronic stress can lead to consistently high levels that can cause dysfunction.

While it seems logical to measure cortisol levels to identify if yours is elevated, levels are highly variable. They can be significantly different from one day to the next, which makes it very difficult to give meaningful insights from a single measurement.

Types of cortisol tests

There are two different types of cortisol tests: salivary and serum.

Salivary cortisol

Research shows that abnormal salivary cortisol readings are associated with poorer metabolic markers of health. Elevated markers–including triglycerides (fat in the blood) and blood glucose–are features of metabolic syndrome, which is associated with a significantly higher risk of developing cardiovascular disease and type 2 diabetes.

While testing cortisol to understand these important markers seems like a natural conclusion, there’s a problem: the readings are too inconsistent for everyday stress monitoring. Let’s say you collect your saliva samples today and get your results back in a few days. If you were to collect the same samples tomorrow, your results would likely look very different.

Your salivary cortisol levels vary greatly from day to day, with research showing variation of 25–50% for morning samples and around 100% for bedtime samples. That level of variability makes it very difficult to draw clear, meaningful conclusions about your stress levels from a single test.

Serum cortisol

Serum cortisol is measured with a blood test. 

Doctors do use serum cortisol to test for two specific conditions: Addison’s disease, where the body doesn’t make enough cortisol, and Cushing’s syndrome, where it makes too much. In both cases, cortisol levels are severely abnormal, which makes them much easier to detect reliably than the subtle day-to-day variations linked to stress.

Tests to understand the impact of chronic stress

While a single cortisol measurement isn’t a reliable way to monitor chronic stress levels, that doesn’t mean you should ignore the impact of stress on your health. Research has shown that chronic stress is associated with an increased risk of cardiovascular disease, type 2 diabetes, and bone fractures.

If you’re concerned about the impact of chronic stress on your health, testing biomarkers for these conditions can give you valuable health insights and the information you need to act.

• HbA1c: This shows your average blood sugar over the last two to three months, which can indicate whether you’re at risk of developing type 2 diabetes. 
• Standard lipid profile: This group of tests includes triglycerides, LDL cholesterol (potentially harmful), and HDL cholesterol (protective). They can help you understand your cardiovascular disease risk.
• Vitamin D: This test measures your levels of vitamin D, a mineral that’s important for bone health. It can help determine if you’re at risk of bone fractures. 

Take our quiz to build a blood test personalised to you.

Evidence-based stress management strategies

Chronic stress can creep up on us. And modern life lends itself to this: juggling a commute, demanding career, family responsibilities, and a social life means the days often feel packed.

Managing your stress shouldn’t feel stressful. These evidence-backed strategies are small tweaks in your daily routine that can help manage your cortisol levels, preventing constant spikes that can lead to dysfunction.

To start out, try one or two, and pick what feels realistic for you.

• Try to exercise regularly: Research has shown that regular physical activity can reduce stress and improve mental health. There isn’t a magic number for amount or intensity. The key is picking something you enjoy that realistically fits into your life.
• Prioritise your sleep: Better quality sleep has been shown to reduce stress levels. Small ‘sleep hygiene’ tips like sticking to the same daily bedtime, limiting alcohol and caffeine near bed, and creating a simple pre-sleep routine can help.
• Try forest bathing: Spending time walking in woodland or green spaces, sometimes called shinrin-yoku, can measurably lower cortisol. A 2019 meta-analysis of 22 studies found salivary cortisol was significantly lower after time in a forest environment compared to an urban one.
• Relieve stress with mindfulness: Mindfulness practices are highly effective at reducing stress. A 2020 systematic review found significant improvements across a range of psychological health outcomes, including stress, anxiety, and depression.

Learn more about simple lifestyle changes to manage stress levels.

Takeaway

In short, while cortisol testing has genuine value in clinical and research settings, the day-to-day variability of results makes it unsuitable for the kind of consistent, actionable insights we aim to provide to individual customers.

Biomarkers like HbA1c, lipids, and vitamin D give a more reliable picture of your stress-related health risks. Implementing evidence-backed lifestyle changes can also help manage your stress levels and reduce cortisol spikes.