Normal blood sugar values, molarity and fluctuations


A variety of stimuli and mechanisms tightly regulate blood sugar levels. This is important for metabolic homeostasis. Levels can fluctuate after a prolonged fast or an hour or two after consuming food. Despite this, the fluctuations are minor. Normal human blood glucose levels remain within a remarkably narrow range.

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Blood sugar fluctuations

In most humans, this ranges from about 82 mg / dl to 110 mg / dl (4.4 to 6.1 mmol / l). Blood sugar levels reach almost 140 mg / dl (7.8 mmol / l) or a little higher in normal humans after a full meal. In humans, normal blood sugar is around 90 mg / dl, which is equivalent to 5 mM (mmol / l).

Since the molecular weight of glucose, C6H12O6, is approximately 180 g / mol, when calculated, the total amount of glucose normally in circulating human blood is approximately 3.3 to 7 g (assuming an ordinary adult blood volume of 5 liters).

In other words, in a healthy adult male weighing 75 kg (165 lbs) with a blood volume of 5 liters (1.3 gal), a blood sugar of 100 mg / dl or 5.5 mmol / l means a total of approximately 5 g (0.2 oz or 0.002 gal, 1/500 of total) of glucose in the blood.

It also means approximately 45 g (1½ ounces) in total body water. Total body water includes more than just blood and typically makes up around 60% of total body weight in humans. 5 grams of glucose is equivalent to a small sachet of sugar or a full teaspoon of sugar.

To be considered non-diabetic, the American Diabetes Association recommends a post-meal glucose level of less than 180 mg / dl (10 mmol / l) and a pre-meal glucose level of 90-130 mg / dl (5 to 7.2 mmol / l). ).

Molarity and mass concentration

Blood sugar is measured in terms of molarity, measured in mmol / L or millimoles per liter. In the United States, and to a lesser extent elsewhere, mass concentration, measured in mg / dL. If a mg / dL figure is converted to mmol / L, it should be divided by 18 or multiplied by 0.055. Likewise, to convert a figure from mmol / L to mg / dL, it is multiplied by 18 or divided by 0.055.

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