Syrup in the vains

This is something I thought about for the first time this week (Back in October). It should be a simple calculation. Amount of blood times blood sugar level.

A normal blood sugar level when fasting (Including after just waking up) is 72 to 99mg/dL.

A normal blood sugar level 2 hours after eating would be below 140mg/dL.

The amount of blood in the body normally accounts for around 10% of the body weight

Given that blood is mainly water its density won’t be far off that of water so it stands to reason that the average 70kg human will have about 7 litres of blood.

Multiplying through this gives a waking total blood sugar of 5g and an after lunch blood sugar of 10g.

Since this is the body’s preferred source of energy, it would be interesting to know how long the body can survive on just the sugar in the blood.

Sugar is about 375 cal/ 100g

That means that we have 38 calories of sugar in our blood after lunch and 19 after fasting.

Assuming a 2000 cal daily energy use the body requires about 1.4 calories/minute. (This happens to be about 100w interestingly enough)

That means that the body has about 13.5 minutes to just under half an hour.



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