As Prof Cheung, an endocrinologist, explains, cortisol is often labelled the “stress hormone,” but from an endocrine perspective, stress represents only one aspect of its broader physiological role. It’s a vital hormone involved in regulating the sleep–wake cycle, blood pressure, metabolism, immune function, and inflammatory responses. These functions are part of normal, healthy physiology rather than indicators of something being wrong.

One of the most common misconceptions patients have is the belief that ongoing stress or fatigue automatically means their adrenal glands are “burnt out.” In reality, cortisol follows a natural daily rhythm, rising in the morning and gradually declining throughout the day. Feeling tired or run-down doesn’t mean the adrenal system is damaged or that cortisol production has failed. In fact, most people who are concerned about having “low cortisol” are found to have normal adrenal function when properly assessed. Stress itself shouldn’t be confused with a cortisol imbalance. While stress can influence how cortisol behaves, it doesn’t necessarily indicate an underlying hormonal disorder.

Even when cortisol levels fall within the healthy range on blood tests, everyday life stress can still affect how people feel. Cortisol responds dynamically to sleep quality, workload, emotional strain, and recovery. When stress is ongoing, this daily rhythm can become subtly disrupted, contributing to symptoms such as fatigue, anxiety, low mood, brain fog, or a sense of feeling overwhelmed, despite test results appearing normal.

Cortisol also interacts closely with adrenaline, inflammatory pathways, and blood sugar regulation. Under chronic stress, these systems may remain in a low-level state of activation, leaving the body feeling persistently on edge. This is why improving sleep, reducing cumulative stress load, and supporting recovery often leads to greater symptom relief than repeated hormone testing when results are otherwise normal.

Just as the heart naturally beats faster during stress, the adrenal glands may release more cortisol in response to life demands. This is a normal, automatic response designed to help the body cope, and the system generally recalibrates once the stress eases. Organs such as the heart and adrenal glands don’t become “burnt out” from stress alone, and there’s no good evidence that supplements can restore or alter their function. In most cases, symptoms attributed to “adrenal fatigue” reflect ongoing stress, disrupted sleep, or insufficient recovery rather than a failure of the adrenal glands themselves.

A cortisol imbalance becomes a medical concern when changes are persistent, pronounced, and begin to disrupt normal body systems, such as blood pressure regulation or blood sugar control. True cortisol-related endocrine disorders sit at the far end of the spectrum and are fundamentally different from the day-to-day hormonal fluctuations associated with stress.

Conditions such as Cushing’s syndrome, where cortisol levels are consistently elevated, may present with features like progressive weight gain, muscle weakness, mood changes, and sustained high blood pressure. Addison’s disease, caused by insufficient cortisol production, is associated with ongoing fatigue, unintentional weight loss, low blood pressure, and can be life-threatening if left untreated.

Importantly, these are rare and serious conditions. They’re identified through formal clinical evaluation and targeted blood testing, typically alongside clear and recognisable physical signs. They’re not diagnosed on the basis of general tiredness, nonspecific symptoms, or online self-assessments. In clinical practice, most people worried about cortisol imbalance are experiencing normal physiological responses to stress rather than an underlying endocrine disorder.

Concerns about “adrenal fatigue” and results from at-home cortisol test kits have become increasingly common in clinical practice. When patients raise these issues, Prof Cheung explains that “adrenal fatigue” isn’t a recognised medical diagnosis endorsed by major endocrine societies. It’s often used as a catch-all label for non-specific symptoms such as persistent tiredness or brain fog, which can have many possible causes.

Home cortisol tests can also be misleading. They rarely account for cortisol’s normal daily variation or the strict standards required for clinical interpretation, which means results may appear abnormal even when adrenal function is intact. While patients’ symptoms are taken seriously, it’s important to distinguish between stress-related experiences and true adrenal disease.

When there’s genuine clinical concern, assessment is done using validated laboratory testing, such as properly timed morning cortisol measurements or stimulation tests, rather than relying on online questionnaires or home kits. This approach helps ensure that medical follow-up is guided by evidence rather than anxiety, and that serious endocrine conditions are neither overlooked nor overdiagnosed.

While average cortisol patterns are broadly similar across sexes, Prof Cheung notes that women may experience distinct variations related to hormonal transitions such as menopause, as well as prolonged stress from chronic illness or caregiving responsibilities. Oestrogen can influence cortisol-binding proteins, which may slightly affect how certain test results are interpreted.

That said, endocrine diagnosis doesn’t rely on symptoms alone. Decisions are based on specific hormone thresholds and functional testing, rather than fatigue, mood changes, or stress-related complaints, which can overlap with many other factors such as burnout, depression, or disrupted sleep. As a result, variations in how people feel don’t necessarily reflect a cortisol disorder, even when life circumstances place sustained demands on the body.

From a clinical perspective, cortisol regulation is largely automatic. The adrenal glands adjust cortisol production throughout the day in response to the body’s needs, without requiring special diets, routines, or supplements. In healthy individuals, this system is generally robust and self-regulating.

That said, overall stress resilience and stable cortisol patterns are supported by well-established lifestyle factors. Consistent sleep, regular physical activity, limiting alcohol intake, and addressing chronic stress through approaches such as mindfulness, therapy, or meaningful social connection can all play a role in supporting the body’s natural hormonal rhythms.

By contrast, there is little credible evidence that supplements marketed for “adrenal support” meaningfully influence cortisol regulation in otherwise healthy people. These products often oversimplify complex physiology and are unlikely to provide benefits beyond those achieved through basic health habits. The body already has the mechanisms it needs to produce and regulate cortisol; what matters most is creating an environment that allows those systems to function as intended.