Why Is My Blood Sugar Still High Even With Medication? The Hidden Cortisol Problem

You're taking your medication. You're watching your diet. Your doctor has tried adjusting your doses. And yet your blood sugar is still high. If this sounds familiar, you're not alone — and there may be a reason your treatment isn't working that has nothing to do with your medication.

A landmark 2025 trial published in Diabetes Care found that 23.8% of people with difficult-to-control type 2 diabetes have hidden hypercortisolism — abnormally high levels of the stress hormone cortisol (Buse et al., Diabetes Care, Dec 2025). A further 25% have elevated cortisol that falls just below the clinical threshold. That means roughly half of people whose blood sugar doesn't respond to medication may have a cortisol problem driving their glucose up.

This article explains how stress and cortisol raise blood sugar, why this connection is so often missed, and what practical steps — including monitoring tools and stress management techniques — can help you take back control.

Key Takeaways

A 2025 study (CATALYST trial, Diabetes Care) found 23.8% of medication-resistant T2D patients have hidden hypercortisolism

Chronic cortisol elevation blocks insulin, releases stored glucose, and keeps blood sugar elevated even when medication is working correctly

Around 75% of people with diabetes experience anxiety or depression, creating a vicious stress-glucose cycle (The Lancet Diabetes & Endocrinology, Dec 2025)

Combining aerobic exercise with mindfulness reduces fasting blood sugar and HbA1c better than either approach alone (PTJ, Oct 2025)

If your blood sugar won't respond to medication, ask your doctor about cortisol screening

What Does Cortisol Actually Do to Your Blood Sugar?

Cortisol is your body's primary stress hormone, released by the adrenal glands whenever you face a real or perceived threat. In the short term, it's useful: it triggers your liver to release stored glucose, giving your muscles quick energy for fight or flight. But when cortisol stays elevated over days, weeks, or months, that glucose release doesn't stop — and your cells become less responsive to insulin, a process called insulin resistance (Ohio State Wexner Medical Center / MESA Study, 2020).

The mechanism works through three interconnected pathways. First, cortisol signals your liver to produce new glucose from non-carbohydrate sources (gluconeogenesis), raising your fasting blood sugar even when you haven't eaten. Second, it reduces the ability of your cells to take up glucose, so the sugar stays in your bloodstream rather than being used for energy. Third, it partially blocks insulin signalling, meaning your medication has to fight harder to do its job.

[INTERNAL-LINK: what is insulin resistance → explainer article on insulin resistance and type 2 diabetes]

Think of it this way. Insulin is a key. Cortisol changes the lock. Even a perfectly working key won't open a lock that's been altered.

Is a Hidden Cortisol Problem Really That Common?

Until 2025, most clinicians considered hypercortisolism a rare complication in diabetes patients. The CATALYST trial changed that picture entirely. Researchers at the University of North Carolina tested 24% of people with difficult-to-control type 2 diabetes and found they had clinically confirmed hypercortisolism (Buse et al., Diabetes Care, Dec 2025). A further group had elevated-but-subclinical cortisol, bringing the total to approximately 50% with meaningful cortisol involvement.

"We always knew it was a potential problem, but we thought it was rare," said Dr. John Buse, the endocrinologist at the University of North Carolina who led the study. "Now, we know it's pretty common."

This matters because hypercortisolism is treatable. Abdominal CT scans in the CATALYST study found adrenal abnormalities in about one-third of participants, with roughly 25% of those having an adrenal tumour — a surgically correctable cause of excess cortisol. For patients without a tumour, cortisol-blocking medication showed a clinically significant reduction in HbA1c in the trial's randomised treatment phase.

[UNIQUE INSIGHT] The CATALYST finding reframes what "treatment-resistant diabetes" means. For decades, doctors and patients alike have assumed persistent high blood sugar despite medication was a failure of willpower, diet, or dosing. The 2025 data suggests that for a substantial portion of patients, the problem isn't insulin management at all. It's an undetected hormonal condition sitting upstream of everything else.

What's the Difference Between Everyday Stress and Clinical Hypercortisolism?

Most people with diabetes who worry about stress don't have a clinical cortisol disorder. That's an important distinction. Everyday psychological stress — work pressure, family difficulties, financial worries — still raises cortisol and still affects blood sugar. But it does so in a more variable, intermittent way. Clinical hypercortisolism, by contrast, is a persistent overproduction of cortisol that doesn't switch off.

Research using population-level data shows the everyday stress effect clearly. A study of civilians in Southern Israel found that glucose levels were 2.10% higher during periods of armed conflict stress compared to baseline days — even across a general population without diabetes (Nature Scientific Reports, 2020). The mechanism is the same whether the stressor is a rocket siren or a difficult performance review. Cortisol rises. The liver releases glucose. Blood sugar climbs.

How Does Work Stress Specifically Affect Blood Sugar Risk?

Occupational stress is a particularly relevant source of chronic cortisol elevation. Research has linked high job strain, defined as high work demands combined with low personal control, to a statistically significant increased risk of developing type 2 diabetes in prospective cohort studies (PMC systematic review and meta-analysis, 2016). The World Diabetes Federation reported in 2025 that 70% of the 589 million people globally with diabetes are of working age, making occupational stress one of the highest-exposure risk environments for glucose dysregulation (The Lancet Diabetes & Endocrinology, Dec 2025).

The flip side also holds. Better workplace conditions protect against diabetes risk. Research published in Diabetes Care found that strong workplace social support was linked to a 25% lower risk of metabolic syndrome in men and reduced circulating inflammatory markers including IL-6 (Diabetes Care / ADA, 2022). Your work environment isn't just affecting your mood. It's affecting your glucose chemistry.

What Is the Stress-Blood Sugar Vicious Cycle?

Stress raises blood sugar. But the relationship runs both ways. Managing diabetes is itself a significant source of chronic stress. About 75% of people with diabetes experience anxiety, depression, or other mental health issues, and around 80% experience what clinicians call "diabetes burnout" at some point in their lives (The Lancet Diabetes & Endocrinology, Dec 2025). That emotional burden feeds back into the cortisol pathway, raising glucose further, which increases distress, which raises cortisol again.

This cycle is called the stress-glucose feedback loop. Globally, diabetes-related distress affects between 18% and 35% of all type 2 diabetes patients, based on multiple validated assessments (Fisher et al., cited in systematic review, Tandfonline, 2024). In clinical settings, approximately 33% of patients show measurable psychological distress, with older patients at highest risk (Dove Medical Press, Feb 2024).

Does Stress Affect Type 1 and Type 2 Diabetes Differently?

The short answer is yes, but not in a simple way. People with type 1 diabetes tend to have a more variable response to stress. Some experience blood sugar spikes during psychological stress. Others see glucose drop, depending on the nature of the stress and their individual physiology. For people with type 2 diabetes, the research is more consistent: stress and elevated cortisol reliably raise fasting glucose and worsen insulin resistance. The MESA longitudinal study found that participants with type 2 diabetes who had a flatter daily cortisol curve (a recognised stress marker) had persistently higher blood glucose over six years (Ohio State / AJMC, 2020).

[UNIQUE INSIGHT] There's a counter-intuitive nuance emerging from newer research. A December 2025 preprint from researchers using CGM and experience sampling found that in non-diabetic adults, higher glucose levels may actually buffer against moment-to-moment stress in daily life — the body's way of ensuring enough energy to cope (Kaduk et al., bioRxiv, Dec 2025). This doesn't apply to people with diabetes, but it helps explain why the stress-glucose relationship is more complex in healthy populations and why CGM studies in non-diabetic users require careful interpretation.

Can Managing Stress Actually Lower Blood Sugar?

Yes — and the evidence is specific. A 2025 randomised controlled trial published in the Physical Therapy Journal tested three interventions in people with type 2 diabetes: aerobic exercise alone, mindfulness therapy alone, and a combined aerobic exercise plus mindfulness program. The combined intervention produced significantly greater reductions in fasting blood sugar, HbA1c, and depression scores than either approach on its own (Aslani et al., PTJ, Oct 2025). Neither aerobic exercise nor mindfulness alone showed a statistically significant difference from each other — but together, the effect was clinically meaningful.

This builds on earlier evidence. A systematic review of mindfulness-based interventions in diabetes found that four of seven reviewed studies successfully lowered HbA1c levels (Noordali et al., cited in ClinicalTrials.gov, 2017). The active MBSR (Mindfulness-Based Stress Reduction) trial at Ohio State (NCT04016415) is testing whether a 6-month mindfulness program can achieve a clinically significant 0.5% absolute HbA1c reduction compared to health education alone.

What Stress Management Techniques Have the Strongest Evidence?

The evidence hierarchy for stress management and blood sugar looks like this, from strongest to emerging:

Combined exercise plus mindfulness produces the best outcomes (PTJ 2025 RCT). The combination works because exercise directly improves insulin sensitivity through muscle glucose uptake, while mindfulness reduces cortisol through HPA axis downregulation. Together they address both ends of the cortisol-glucose link.

Mindfulness-based stress reduction (MBSR) has a consistent track record in 4 of 7 reviewed trials of reducing HbA1c. Eight-week structured programs, now available online, are the most studied format.

Social support is underappreciated. Workplace social support alone reduced IL-6 inflammatory markers and cortisol reactivity in research settings (Diabetes Care, 2022). The mechanism: perceived safety reduces HPA axis activation. Isolation does the opposite.

Sleep matters more than most people realise. Cortisol should drop at night. In people under chronic stress, it doesn't. Staying elevated through the night raises fasting glucose by morning — a common pattern in people who can't understand why their pre-breakfast reading is high despite not eating since dinner.

How Can You Tell If Cortisol Is Affecting Your Blood Sugar?

There's no single consumer-accessible test for chronic cortisol elevation, but there are patterns worth discussing with your doctor. Persistent high fasting glucose despite medication is the clearest signal from the CATALYST trial. If your blood sugar responds to medication for a period and then stops responding, or has never responded adequately despite multiple adjustments, cortisol may be a factor worth investigating.

CGM data can also reveal cortisol-driven patterns. Cortisol follows a circadian rhythm, peaking in the early morning and falling at night. In people with normal cortisol, fasting glucose is typically at its lowest in the late evening. If your CGM shows that your glucose rises sharply through the night without any eating, that nocturnal cortisol elevation may be the cause. "Cortisol is driving glucose changes, and it does make diabetes much harder to control. Naturally, cortisol levels should be going lower in the evening. But people with stress have higher cortisol levels and blood sugar at night," explained Dr. Joshua Joseph, lead researcher of the MESA cortisol-glucose study (Franciscan Health, 2020).

[INTERNAL-LINK: how to read your CGM data → guide to understanding time-in-range and overnight glucose trends]

A blood or urine cortisol test, or the dexamethasone suppression test used in the CATALYST trial, can confirm clinical hypercortisolism. These are not standard diabetes screening tests. You may need to specifically ask your endocrinologist or GP whether cortisol screening is appropriate for your situation — particularly if you've been on multiple medications with limited results.

Frequently Asked Questions

Can stress alone cause type 2 diabetes if I don't have it yet?

Chronic stress is a recognised risk factor for developing type 2 diabetes, not just for worsening it. A systematic review and meta-analysis found that high job strain — high demands combined with low control at work — is associated with a significantly increased risk of T2D in prospective cohort studies (PMC, 2016). Stress doesn't cause diabetes on its own, but chronic cortisol elevation worsens insulin resistance and glucose metabolism over time, lowering the threshold at which other risk factors push someone into diabetes.

Why does my blood sugar spike in the morning even though I haven't eaten?

This is called the "dawn phenomenon" and cortisol is the primary driver. Your cortisol level naturally peaks in the early morning to prepare your body for waking. This signals the liver to release stored glucose, raising your fasting blood sugar before you eat anything. In people under chronic stress, this morning cortisol spike is higher and lasts longer, producing elevated pre-breakfast readings that medication alone may not fully control. CGM is particularly useful for identifying this pattern. [INTERNAL-LINK: dawn phenomenon explained → article on morning blood sugar spikes]

Will mindfulness cure my diabetes?

No. Mindfulness is an adjunct to — not a replacement for — medical treatment. But the evidence that it actively improves glucose control is meaningful. Four of seven reviewed mindfulness intervention studies reduced HbA1c levels (Noordali et al.), and the 2025 PTJ trial found that combining mindfulness with aerobic exercise produced superior glycaemic outcomes to either approach alone (Aslani et al., PTJ, Oct 2025). Treating stress is treating diabetes. The two are not separate problems.