Blood Sugar

Blood sugar is a term which in colloquial usage refers to the amount of glucose present in a mammal's blood. However, the term, if used in a physiological context, is a misnomer and misleading because other sugars besides glucose are always present. However, since these other sugars are largely inert, and only glucose serves as a controlling signal for metabolic regulation, the term has gained some currency and is used by medical persons and lay persons alike. Glucose, transported via the bloodstream from the intestines or liver to body cells, is the primary source of energy for the body's cells.

Blood sugar concentration, or glucose level, is tightly regulated in the human body. Normally, the blood glucose level is maintained at a reference range between about 4 and 6 mM (mmol/l). The normal blood glucose level is about 90mg/100ml, which works out to 5mM (mmol/l). The total amount of glucose in circulating blood is therefore about 3.3 to 7g (assuming an ordinary adult blood volume of 5 litres, plausible for an average adult male). Glucose levels rise after meals for an hour or two by a few grams and are usually lowest in the morning, before the first meal of the day.

Failure to maintain blood glucose in the normal range leads to conditions of persistently high (hyperglycemia) or low (hypoglycemia) blood sugar. Diabetes mellitus, characterized by persistent hyperglycemia from any of several causes, is the most prominent disease related to failure of blood sugar regulation.

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