Diabetes Mellitus: Part 1 – Understanding Glucose and Insulin

In a previous blog post, I explained the relevance of metabolic syndrome to mental health nursing. Elevated fasting blood glucose is a diagnostic criterion of metabolic syndrome, and is caused by a steady increase in insulin resistance. Without intervention or a change in lifestyle, this is likely to develop into Type 2 Diabetes Mellitus (DM2). But what exactly does insulin do, and why do we need it?

First of all, we need to understand the role of glucose. For our cells to function, they need a continual supply of chemical energy (in the form of Adenosine Triphosphate, or ATP). The most straightforward way in which ATP can be generated is by the cellular metabolism of glucose.

Glucose circulates in varying concentrations in our bloodstream. It can be obtained directly from our diet, but is more likely to be converted into glucose by the body from other carbohydrates:

Even fructose (found in high concentrations in soft drinks) needs to be converted into glucose before cells can use it as an energy source.

So what about insulin? The video below should help to explain. From this you should be able to answer the following questions:

  • What is insulin an example of?
  • Where is it produced, and by what cells?
  • What prompts the release of insulin?


The video also states two functions of insulin – the facilitation of glucose influx from the bloodstream to cells, and the formation of glycogen (a complex carbohydrate in animals that is similar to the starch found in bread, pasta and rice). However, insulin’s functions are more widespread than this. I like to think of insulin as a bit like a construction site manager; overall, it facilitates the building and movement of materials. Here is a more comprehensive list of its functions, together with what the net effects of these functions are:

Insulin’s Function Insulin’s Effect on the Body
Facilitates glucose influx into cells

Allows cells to produce energy via ATP production

Reduces levels of glucose in the bloodstream

Prompts the creation of glycogen (glycogenesis)

Prevents the breakdown of glycogen to form new glucose molecules (gluconeogenesis)

Increases glycogen levels in muscle and the liver

Reduces levels of glucose in the bloodstream

Prompts the creation of lipids (lipogenesis)

Prevents the breakdown of lipids into fatty acids and glycerol (lipolysis)

Increases the volume of adipose tissue

Reduces the concentration of fatty acids in the bloodstream

Prompts the creation of new muscle tissue from amino acids

Prevents the breakdown of muscle tissue

Increases muscle mass

Of note, glucagon has virtually the opposite function of insulin. It’s released by alpha cells from the pancreas when blood glucose levels are low. The only thing it doesn’t do in opposition to insulin: it doesn’t facilitate muscle breakdown (you wouldn’t want your muscles to atrophy every time you were hungry, would you?!).

It’s important to acknowledge the full extent of what influences insulin has. It makes it much easier to explain what happens when the body loses its ability to create insulin (DM1) or when the body becomes resistant to insulin’s presence (DM2). This is what I will be focussing on in my next post.


Picture credits:
Carbohydrate Digestion (2016) by Nutritional Doublethink. From Flickr.


Posted by Ben Murphy

Ben is a registered mental health nurse, holds an MSc in Genetic Counselling, and is a lecturer in Biological Sciences at City, University of London. Amongst other things, he teaches anatomy, physiology, pathophysiology and therapeutics to pre-reg. and post-reg. nursing students.

  1. Irene Lukanga June 7, 2021 at 11:42 am

    Very well explained Ben. Thank you


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