The pathophysiology of "happy" hypoglycemia.

Background: Hypoglycemia usually includes various neurological symptoms, which are the consequence of neuroglycopenia. When it is severe, it is associated with altered mental status, even coma.
Case Presentation: We report the case of a patient with severe hypoglycemia, completely asymptomatic, due to the increase of lactate production in response to tissue hypoperfusion following a hemorrhagic shock. This illustrates that lactate can substitute glucose as an energy substrate for the brain. It is also a reminder that this metabolite, despite its bad reputation maintained by its role as a marker of severity in critical care patients, has a fundamental role in our metabolism.
Conclusions: Following the example of the "happy hypoxemia" recently reported in the literature describing asymptomatic hypoxemia in COVID-19 patients, we describe a case of "happy hypoglycemia."