What causes the dawn phenomenon in insulin resistance and diabetes?
The dawn phenomenon refers to an early-morning rise in blood glucose (typically between 3–8 a.m.) driven by hormonal signals, including cortisol, growth hormone, and adrenaline. It is not primarily caused by late-night eating, although lifestyle habits can influence its magnitude.
Pop Quiz for Clinicians
True or False:
The “dawn phenomenon” observed in patients with insulin resistance is primarily an effect of nighttime snacking and can be mitigated by ensuring the last meal is consumed 3–4 hours before sleep.
(Answer at the end.)
What a Continuous Glucose Monitor Taught Me
Last year I experimented with wearing a continuous glucose monitor (CGM) and it was eye-opening.
One of the things I learned was that even a small amount of rice causes a large spike in my blood glucose, while something like dark chocolate barely moves the needle.
Given my family history and South Asian predisposition to type II diabetes, those insights helped me create a more tailored lifestyle approach to metabolic health.
CGMs can reveal metabolic patterns that routine labs often miss.
But one thing that became increasingly clear is that metabolic health isn’t just about food. Sleep plays a major role as well.
Watch the Interview
This week we’re diving deeper into metabolic health and sleep with preventive endocrinologist Chhaya Makhija, MD.
Dr. Makhija is the founder of Unified Endocrine and Diabetes Care in California, and a colleague with whom I’ve shared patients.
If you see patients with insulin resistance, metabolic syndrome, or unexplained fatigue, this conversation includes several practical clinical pearls worth watching.
Prefer watching? The full interview is below.
Key Clinical Insights from the Conversation
Sleep Is an Overlooked Vital Sign in Metabolic Health
One of the most important takeaways from the discussion is that sleep deserves the same clinical attention as diet, exercise, and laboratory markers.
“Sleep is an important vital sign.”
Sleep Disruption Can Worsen Insulin Resistance
Poor sleep does not simply affect daytime fatigue.
It directly influences metabolic regulation.
“Poor sleep directly and indirectly affects glucose control, insulin resistance, and metabolic health.”
Sleep fragmentation increases stress hormones such as cortisol and adrenaline. These hormones signal the liver to release more glucose into the bloodstream.
Over time, this can increase insulin demand and contribute to metabolic dysfunction.
Cortisol and Stress Hormones Affect Overnight Glucose
Stress physiology can significantly affect nighttime glucose levels.
“Cortisol tells the liver to produce more glucose—even when you're not eating.”
This process helps explain why patients may see elevated fasting glucose levels despite making dietary improvements.
Circadian Rhythm Stability Matters for Hormone Health
Sleep timing is another important factor in metabolic regulation.
“Consistent wake-up times help keep cortisol, growth hormone, insulin, and glucose metabolism in sync.”
Irregular schedules, shift work, and inconsistent sleep timing can disrupt these hormonal rhythms.
Using CGMs as a Clinical Education Tool on
Continuous glucose monitors can provide powerful behavioral feedback for patients.
However, interpretation requires context.
“The goal is not to chase perfect numbers but to learn patterns.”
For example, one of the simplest lifestyle interventions Dr. Makhija recommends is movement after meals.
“Simple activity after meals can lower glucose by 20–30 mg/dL.”
Breathwork and Stress Physiology
Another interesting clinical insight is the role of nervous system regulation.
Dr. Makhija often recommends brief breathing practices:
- when patients wake up
- before bedtime
These practices activate the parasympathetic nervous system, which may help stabilize stress physiology and glucose regulation.
The Dawn Phenomenon Explained
Many patients with insulin resistance or diabetes experience the dawn phenomenon, which appears clearly in CGM data.
“The dawn phenomenon is the rise in blood glucose before waking, driven by cortisol, adrenaline, and growth hormone.”
This physiologic glucose rise occurs even in the absence of food intake.
Lifestyle interventions that may help reduce its impact include:
- finishing dinner 3–4 hours before sleep
- taking a short walk after dinner
- incorporating stress-reducing practices before bed
Sleep Disorders and Hormonal Health in Men
Sleep disorders can also influence reproductive hormones.
Untreated sleep apnea and metabolic dysfunction can contribute to:
- erectile dysfunction
- reduced libido
- lower testosterone production
“The body prioritizes survival hormones like cortisol over reproductive hormones during chronic stress.”
This is another example of how sleep and metabolic health are closely connected.
Dr. Makhija goes into more detail in the interview about which labs to order and how to evaluate suspected testosterone deficiency, so be sure to watch the full discussion if this is something you encounter in your practice.
Why Sleep Should Be Part of Every Metabolic Evaluation
For clinicians treating metabolic disease, sleep evaluation can provide critical diagnostic clues.
Sleep issues may present as:
- fatigue
- insomnia
- depression
- hyperarousal or “tired but wired” symptoms
- worsening glucose control
Addressing sleep health may help identify upstream drivers of metabolic dysfunction.
Pop Quiz Answer
False
The dawn phenomenon is a physiologic rise in glucose in the early morning hours (approximately 3–8 a.m.), driven by hormonal signals such as cortisol and growth hormone.
While lifestyle habits such as earlier dinners may influence glucose patterns, the underlying mechanism is hormonal rather than dietary.
Further Learning
Did you learn something today?
Clinicians interested in earning CME/CE credit through reflection-based learning can explore the Learner+ platform here:
https://champions.learner.plus/?champion=Dr%20Nishi%20Bhopal
