What is diabetes? Understanding the role of insulin and diabetes symptoms

In 2015, The International Diabetes Federation reported that more than 400 million people were living with a disease called diabetes. In the UK, we spend £10B every year treating diabetes and its complications—which equates to about £20,000 every minute. But where does diabetes come from, what is it, and what are its symptoms? This article will dive into these questions as well as explore insulin, the magic hormone that goes awry in diabetes.

So… what is diabetes?


Diabetes is a condition where blood glucose (or blood sugar—two different names for the same thing) levels are too high over a sustained period of time. It’s perfectly normal to have elevated blood glucose levels after eating, but diabetes is when they don’t come back down to normal levels. There are two main causes of diabetes: Either your body doesn’t produce enough insulin, which is what we call type 2 diabetes, or your body can’t produce any insulin at all, which is called type 1 diabetes. Ninety percent of people with diabetes have type 2, which will be the focus of this article.

But let’s first take a step back… what is insulin and how does it link with sugar levels?

It all begins with one of the more curious, and not often talked about, organs in the body: the pancreas. It sits behind your stomach, is about 6 inches long, and looks a bit like a feather made of jelly (what a visual, eh?). The pancreas does many amazing jobs (including being the main organ for producing the enzymes that digest all our food), but one of its key responsibilities is to control the levels of sugar in our bodies.

The pancreas coordinates a beautiful feedback loop in the body that keeps blood sugar tightly controlled. 

After we eat a meal, the various macronutrients in our food (like fats, proteins, and carbohydrates) get broken down into glucose and absorbed into our bloodstream. When  blood glucose levels go up, the pancreas releases a hormone called insulin, which tells your body to store that sugar as fat in lots of places (e.g. around your organs, in your muscles, or—more obvious to the naked eye—under your skin). By storing this sugar in different places, our blood glucose levels are lowered down and, voila, back to a normal, healthy range.

If, however, we skip a meal and our blood glucose level goes down, the pancreas releases a hormone called glucagon. This hormone is basically the opposite of insulin—it tells our body to break down stored sugar and therefore bring blood glucose up to normal levels.

While you go about your day, whatever you’re doing, the pancreas is always working to keep your blood glucose finely balanced so that you have enough energy to power your muscles, brain, and other organs, but not too much. As we’ll soon find out, elevated blood sugar levels can lead to a separate set of negative impacts.

When someone develops type 2 diabetes, their pancreas loses the ability to secrete insulin, and therefore, to keep sugar levels balanced.

What causes type 2 diabetes?

It all starts with energy (or calorie) excess. When the body consumes excess calories, it needs to do something with that extra energy, so we tend to store it rather than getting rid of it like we do some other nutrients.

The body is really excellent at storing energy. Initially, we store glucose in the liver and muscles. But once those storage deposits are full, we need to store it somewhere else... and that’s when the insulin we secrete turns that excess sugar into fat.

The “fat” we usually think about is stored under our skin. However, invisible to the naked eye is fat stored around and inside our organs. This is the problematic fat that is seen in type 2 diabetes.

Fat deposits around the pancreas are toxic to the cells which produce insulin. The feedback cycle carried out by the pancreas through insulin secretion stops, pushing our blood glucose up further and further, and eventually causing all of the complications created by type 2 diabetes.

It was thought for many years that, once these cells stopped producing insulin, they’d never again be able to. But we have great news! Recent research has shown that type 2 diabetes is actually reversible in many cases. There’s too much to say about that for this article, so we’ve written another about it here.

What are the symptoms of type 2 diabetes?

When your pancreas stops being able to produce the insulin needed to keep blood glucose levels at bay, the body takes charge and attempts to dispose of the excess glucose in the form of urine. In some people, this can lead to the following symptoms, though it’s worth noting that 6 out of 10 people have no symptoms when they are first diagnosed with diabetes.

  • Going to the toilet a lot, especially at night
  • Excessive thirst
  • Fatigue
  • Genital itching or thrush
  • Cuts and wounds taking longer to heal
  • Tingling, numbness, or pain in the hands and feet
  • Blurry vision
  • Increased hunger
  • Frequent infections
  • Areas of darkened skin, usually in the armpits or neck

If these symptoms weren’t unpleasant enough, the complications of type 2 diabetes can be life-threatening (we’ve even written a whole post about them).