Blood Sugar and Stress: Why They Rise Together

Medically reviewed by Tracy McCarthy, MD - Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner

The Anxiety That Comes Out of Nowhere

You weren't particularly worried about anything. The meeting went fine. And yet there it is a racing heart, a low hum of dread, that feeling of being vaguely on edge with no clear reason.

For many of the patients I work with, this pattern has a physiological explanation that has nothing to do with their thoughts. It has to do with what happened metabolically — sometimes hours earlier.

Blood sugar and stress hormones don't operate in separate lanes. They are deeply, bidirectionally connected. And understanding that connection can reframe a lot of what you thought was purely psychological.

How Cortisol Raises Blood Sugar

When your brain perceives a stressor - a deadline, a difficult conversation, a night of poor sleep, even skipping a meal — the HPA axis activates and cortisol is released. One of cortisol's primary functions is to raise blood glucose, providing the body with fuel to respond to the perceived threat.

A review published in the International Journal of Molecular Sciences (https://pmc.ncbi.nlm.nih.gov/articles/PMC9331414/) describes the mechanisms in detail: cortisol promotes hepatic glucose production, stimulates glycogenolysis, and impairs insulin receptor signaling — meaning it simultaneously pushes more glucose into the bloodstream and makes it harder for cells to use that glucose effectively. The result is elevated blood sugar in the context of stress, even without any food intake.

In the short term, this is adaptive. In chronic stress, this cycle never fully resets. Blood sugar stays elevated higher than it should, and the insulin response that follows can push it too low — triggering another round of cortisol and adrenaline release.

How Blood Sugar Instability Creates Stress

The relationship runs in both directions. When blood sugar drops below a threshold, the body releases adrenaline - epinephrine - to mobilize stored glucose and bring levels back up.

A study published in The Journal of Clinical Endocrinology & Metabolism (https://academic.oup.com/jcem/article/109/2/e675/7274067) found that individuals with insulin resistance show an accentuated HPA axis response even to modest glucose lowering - meaning their stress response activates at blood sugar levels that wouldn't trigger a response in someone with healthy metabolic function.

That adrenaline creates a physical experience: racing heart, shallow breathing, difficulty settling, sense of dread. This is biochemically identical to anxiety. For patients who describe sudden, unpredictable anxiety — particularly anxiety that feels physical rather than worry-driven, that often occurs at the same time of day, or that improves after eating — this mechanism is worth investigating.

Why This Matters for Mental Health

In conventional psychiatry, anxiety is evaluated and treated at the psychological level. In functional medicine, we also ask: what is happening metabolically that may be contributing to or amplifying this presentation?

Blood sugar instability is one of the most consistently underrecognized physiological contributors to mood symptoms. It does not explain every case of anxiety. But in a meaningful proportion of individuals, addressing the metabolic picture - protein intake, meal timing, reduction of refined carbohydrates, and evaluation of fasting insulin - produces changes in mood stability that therapy and medication alone had not achieved.

This is not an either-or. It is an expansion of the investigation.

Small Steps to Consider

• Prioritize protein at breakfast — it stabilizes blood sugar through the morning and reduces early cortisol reactivity in some individuals

• Track mood and energy two to three hours after meals — timing can reveal a blood sugar pattern

• Reduce refined carbohydrate intake at lunch if afternoon anxiety or energy crashes are consistent

• Avoid caffeine on an empty stomach — it can raise cortisol first thing, before the stabilizing effect of food

• Discuss fasting insulin testing with your provider — standard glucose testing alone may miss early blood sugar dysregulation

A Final Thought

You're not overreacting. You're not imagining it. Your body's stress response and your blood sugar are in constant communication — and when that system is dysregulated, the effects are felt in mood, energy, focus, and sleep.

Understanding this connection is not about adding more to your plate. It's about getting a more complete picture of what may be driving your symptoms.

To start mapping your own patterns, my free Root Cause Health Assessment (https://health-report.scoreapp.com/) is designed to help you connect the dots across mood, metabolism, energy, and more.