Blood sugar — what you need to know

Blood sugar is a term which has become increasingly familiar to us over the last two decades, but what does it actually mean?

The terms blood sugar and blood glucose are used synonymously and mean the same thing. Literally, they mean the amount of glucose present in our blood, you may hear it as serum glucose level, blood glucose level or even just blood sugars. But effectively they are all describing the same thing.

Blood glucose levels are central to the overall health of our bodies and are particularly crucial to those who have diabetes.

What is glucose?

When we talk of blood sugar what we’re referring to is glucose. Glucose is a simple sugar, also known as a monosaccharide, which circulates in our bloodstream and is stored in our body as glycogen. The chemical formula for glucose is:

Figure 1. The chemical formula for glucose.

This means that to make up one glucose molecule you need 6 carbon (C) atoms, 12 hydrogen (H) atoms and 6 oxygen (O) atoms.

Normally, there is around 4 grams of glucose circulating in our body at any one time and keeping our blood glucose/sugar levels under control is a tightly regulated process.

The process is called homeostasis and is responsible for regulating many of the body’s functions. In other words, homeostasis means the stable condition of an organism’s internal environment.

Two hormones are important in the regulation of blood glucose; insulin and glucagon.

Both hormones are secreted by the pancreas and are released in response to the levels of glucose in our blood.

Low blood glucose

Generally, our blood glucose levels may be low when we are between meals or when we have exercised. Therefore, glucagon is secreted by the alpha cells in the pancreas, its release triggers the liver to release more glucose into the bloodstream.

It also encourages the liver to make glucose from other nutrients we have in our body such as protein. Once the liver has released enough glucose our blood sugar levels will return to normal.

Several things can cause our blood sugar levels to fall including:

  • Missing a meal
  • Eating a meal which is low in carbohydrates
  • Alcohol
  • High levels of exercise
  • Side effects of other medications

High blood glucose

When high levels of glucose are detected in the blood, the beta cells in the pancreas release insulin. We always have a small amount of insulin in circulation, however when our sugar levels increase so do the levels of insulin.

Insulin effects several cells in the body such as muscle cells, red blood cells and fat cells. So, when insulin in detected these cells absorb glucose from the blood, thus lowering blood glucose levels.

Glucose levels can rise when:

  • We eat a carbohydrate heavy meal
  • There is a lack of exercise
  • We have an infection or illness
  • There is a change in our hormone levels e.g. periods
  • We are under stress

Not everything about glucose is bad. Our brain depends on glucose as its main source of energy and for this reason its regulation is vital.

Without efficient regulation our brain physiology can become severely affected. Nerve cells require the most energy and so need a continuous delivery of glucose from the blood. Some studies have identified that bioenergetic defects may be important pathophysiological mechanisms in many disorders.

Alzheimer’s disease progression has been associated with a disturbance in glucose metabolism. One of the first signs of Alzheimer’s is also a lower level of cerebral glucose metabolism.

In Parkinson’s disease, the dysregulated pathways have shown to be closely linked to those of type 2 diabetes. There is an increased risk of those suffering with type 2 diabetes, characterised by high glucose levels, to develop Parkinson’s disease. Therefore, dysregulation in glucose metabolism has been shown to increase the risk of cognitive impairment in some cases.

Overall, we need to keep our blood glucose levels in check to avoid potentially serious health complications. A major consequence of uncontrolled blood glucose levels is the development of type 2 diabetes.

The body’s inability to effectively metabolise glucose can result in:

  • Nerve disorders or neuropathy
  • Eye problems or retinopathy
  • Cardiovascular disease
  • Kidney problems

However, these complications usually take a few years to fully develop and so type 2 diabetes is often left undiagnosed until its later stages.

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