Why Blood Glucose Cannot Be Left Alone | AI Learning Guide

Start with the number itself. In a fasting adult, blood glucose is held near seventy to one hundred ten milligrams per deciliter. That range is not arbitrary. The brain and red blood cells burn glucose continuously and cannot fall back on fat the way muscle can, so when glucose drops toward fifty, neurons run short and consciousness is threatened. Push the other way, above roughly one hundred eighty, and the kidney can no longer reclaim all the filtered glucose. It spills into urine and pulls water with it. The body is defending a narrow corridor between those two failures, and it has to do so even though meals arrive in pulses while demand never stops.

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The defended range

Blood glucose is the plasma concentration of glucose. In a healthy fasting adult it is held near 70-110 mg/dL, and after a meal it usually stays below about 140 mg/dL. Homeostasis means keeping the value inside that band despite large swings in intake and use.

Two failure directions

The brain and red blood cells consume glucose continuously and cannot substitute fat for it. When glucose falls too far, neuronal fuel runs short and consciousness is threatened. When glucose rises too far, the kidney can no longer reclaim all of it, glucose appears in urine, and osmotic water loss follows. The narrow band is the space between those two problems.

Intermittent supply, continuous demand

Meals deliver glucose in pulses, but tissues draw on it every minute. A storage-and-release system is therefore required, not just a sensor.

References

[1]Blood Glucose - MedlinePlus Medical Encyclopediamedlineplus.gov