Written by Dr Katie Stephens, GP

Dr Katie graduated from the University of Manchester in 2007 (MBChB) and completed her GP training in the West Midlands in 2012 (MRCGP). 

How are sugar levels normally controlled?

The cells in our body use sugar (glucose) as an energy source to help them function. Much of the glucose comes from foods that we eat, even foods that don’t taste sweet. Some of it can come from extra that we have stored in our bodies. Usually, the amount of glucose being carried around in our bloodstream can vary by a reasonable amount within a ‘normal range’. It is affected by factors such as what someone has eaten, how long ago they ate, and how active they have been.

When the sugar level fluctuates above or below where it should be, this is sensed by our pancreas, which then responds by releasing a hormone to bring the level back towards normal. The pancreas is an internal organ, roughly the size of your hand, located in the top left of your abdomen, tucked just below your stomach. When the sugar levels are too high, the pancreas releases a hormone called insulin to bring them down. When they are too low, the pancreas releases a hormone called glucagon to bring them up.

Let’s look at an example of how the pancreas works when the sugar levels drop: imagine you have just run 5k. The muscles in your legs will have used up lots of the available sugar to give them energy to run that far. This leads to a drop in the blood sugar level. The pancreas senses this and releases a hormone called glucagon.

Glucagon then travels around all the body, including going to the liver. The liver acts as our body’s own kitchen cupboard and stores away a lot of sugar in case it is needed later. Glucagon tells the liver to do the following:

• Release some of this sugar back into the blood stream
• Stop picking the glucose out of the blood stream to store away
• Break down other energy sources (amino acids) to make more glucose

The net result is that the amount of sugar released into the blood stream then increases back up to a normal range.

Conversely, if sugar levels rise too high, our pancreas secretes the hormone insulin. This might happen if we have just eaten, although sometimes just seeing or smelling something tasty can trigger insulin release.

Insulin has the opposite effect of glucagon, and it lowers the blood sugar levels in the following ways:

• Telling our cells to open up and pull in some of the glucose from the bloodstream. (This is important as it means the cells then have the energy they need to work properly.)
• Telling our liver to store more glucose, thereby taking it out of circulation.
• Using glucose to make and store fats and cholesterol.

When our bodies make and release insulin and glucagon properly, this means that the ideal amount of sugar circulates round in our blood, and can also get into cells, where it is used as energy.

In Type 1 Diabetes, there isn’t any insulin at all. In Type 2 Diabetes, there is less insulin than normal and/or our body doesn’t respond normally to the insulin that is present. Both types lead to problems linked to blood sugar levels being too high. For more information, see our Guide to Type 1 Diabetes here and Type 2 Diabetes here.

References

1. Rix I, Nexøe-Larsen C, Bergmann NC, et al. Glucagon Physiology. [Updated 2019 Jul 16]. In: Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279127/
2. Wilcox G. (2005). Insulin and insulin resistance. The Clinical biochemist. Reviews, 26(2), 19–39. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1204764/
3. https://www.kinetikwellbeing.com/definitive-guide-for-type-2-diabetes/
4. https://www.kinetikwellbeing.com/definitive-guide-for-type-1-diabetes/