Why Your Blood Sugar Is Highest in the Morning, Even When You Fast

Summary

The video explains why blood glucose can rise in the morning despite an overnight fast. Before dawn, hormones including growth hormone, cortisol, and adrenaline signal the liver to release stored sugar (glycogen) to prepare the body to wake and be active. This normal “dawn phenomenon” can occur in people without diabetes, while type 2 diabetes may make the rise larger.

The video also describes why glucose may decline slowly during a longer fast: muscles can shift toward using fat for fuel, leaving more glucose available for the brain. A stubborn reading during a longer fast is not, by itself, proof that anything is wrong.

Practical takeaways

• Don’t treat one morning reading as a verdict. Look at readings taken consistently over several mornings and consider the pattern or average.
• Measure consistently. Use the same method and time, after at least eight hours without calories.
• Use glucose sensors mainly to follow trends. A study discussed in the video found that one arm sensor read lower than finger-prick results in the participants tested. Confirm a surprising result with an appropriate blood test rather than reacting to a single sensor reading.
• Know the lab ranges cited in the video. Fasting results of 100–125 mg/dL are in the prediabetes range, and 126 mg/dL or higher are in the diabetes range. One high result does not establish a diagnosis; a clinician may confirm it with another test, such as a repeat fasting test or A1C.
• Discuss repeated fasting lab results of 100 mg/dL or higher with a doctor. Seek medical advice for symptoms such as persistent excessive thirst or frequent urination.
• If you take medication that lowers blood sugar, follow your clinician’s plan. The video is not medication advice.

Presenters and sources

• Presenter/narrator: Fred (Fasted Fred)
• Sources cited in the video: 1984 study in Diabetes; 2013 study in Diabetes Care; 2012 study in the American Journal of Physiology; 2024 study in Sensors; American Diabetes Association.