Blood sugar: understanding glycemia and insuline

sugar and fat - comic

Many health subjects relate to sugar. So it’s important to understand properly the basics mechanisms around it. It can become quickly complex, but I will only detail here the basics about sugar in the body.

The organs in stake

Let’s quickly locate the involved organs: the stomach, the liver and the pancreas. And for that, nothing is better than a quick drawing:organs liver pancreas stomach - comic

Where does the sugar that you eat go?

The sugar that we swallow during a meal is quickly released in the blood as glucose. Sugar can have several forms: glucose, fructose, galactose, sucrose, lactose, maltose… If it is not glucose, the transformation will take place in the liver so that the sugar released in the blood is glucose only.

That level of glucose in the blood is called Glycemia.

how sugar goes into blood

And then?

Then, glucose will enter the muscle cells to provide energy. Above a certain level, the excess of glucose will be store in the liver as glycogen. Above an even higher level, glucose can be turned into fat. Glucose is therefore energy, used in 3 different ways depending on the quantity provided:

  1. Energy is directly available in the muscles
  2. Energy excess is stored in the liver for short term use (a few hours)
  3. Energy excess is stored as fat for long term (several days, or years, we know that!)

Sugar blood level

By all means, the body has to regulate the quantity of sugar in the blood in order to keep a stable level. That is what we call homeostasis.

Hyperglycemia is the excess of glucose in the blood. Hypoglycemia is a too low level of glucose in the blood. Both are dangerous for the body.

Thus, like we saw before, if the sugar blood level is high, the excess of energy will be store for later.

If, on the opposite, the sugar blood level is too low, the liver will then release its stocks (glycogen -> glucose) in order to restore a proper level.

Once the liver is depleted from glycogen, the fats are turned into energy fuels.

3 levels of energy

To sum up, we’ve seen 3 levels of energy:

  1. Glucose, available immediately
  2. Glycogen, stored in the liver, can be turned into glucose
  3. Fat (lipides/glycérides), stored in the fat tissues, can be turned into energy fuels

3 energy levels

What about the fat that we eat? Digestion will turn the fat into energy fuels. If no glucose nor glycogen is available (low insulin), those fuels can be used. Otherwise, they are stored as fat. When the body can choose, sugar is definitely the easiest source of energy compared to fat – the easiest, but not necessarily the best.

The role of pancreas

The pancreas is the supervisor. He enables every one to coordinate, using two hormones that it releases into the blood: insulin and glucagon.


When the pancreas notice that the sugar blood level is too high, it releases insulin. It is thanks to insulin that glucose can enter the muscle cells, or be transformed into glycogen by the liver, or stored as fat. Without insulin, the glucose cannot be used at all.


Glucagon has the opposite effect of insuline. When the sugar blood is too low, the pancreas releases glucagon. This latter tells the liver to transform its glycogen into glucose and deliver it into the blood. It also tells the fat to be converted into energy fuels. Those energy fuels can run without insuline.

So insulin indicate that energy excess has to be stored, while glucagon indicates that storage has to be used for energy.

liver pancreas insuline glucagon

What is the minimum amount of sugar that the body needs per day?

Zero. The body can work perfectly fine without any sugar intake. It then transforms fat into energy fuels, which provide the sufficient energy.

Can we get fat without sugar?

Nope. Fat storage involves insuline. Insuline is released when the sugar blood level rises. The sugar blood level can raise only from eating carbohydrates. However, there can be exceptions: some factors can trigger insuline release like stress or coffee.

That’s it, you now know the basics to understand many concepts like diabetes type I or II, insuline resistance, intermittent fasting, etc.

If you like that kind of article, don’t hesitate to tell me in the comments!

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