Trait overview: Fasting blood glucose

Monday, April 6, 2020. Author Alex Auld

Trait overview: Fasting blood glucose

What is glucose?

Glucose is a simple sugar (or ‘monosaccharide’) derived from the breakdown of carbohydrates.

Through a process called cell respiration, cells in our body use glucose to generate energy in the form of a molecule called ATP (adenosine triphosphate). ATP is often referred to as the ‘energy currency’ of our cells, and is required for muscle contraction, growth and almost all cellular processes needed to sustain life.

Glucose is absorbed into the bloodstream by the small intestine, once it has been broken down from the larger carbohydrate molecules, including polysaccharides (long-chain sugars e.g. starch) and disaccharides (two-chain sugars e.g. sucrose). Glucose is then delivered to other tissues such as the liver and skeletal muscles, where it can be used to generate ATP, or be built up into energy storage molecules (e.g. glycogen).

What is insulin?

Insulin is an important hormone which allows various tissues (especially muscle and fat) to take up and use glucose from the bloodstream. Without it, tissues and organs would be deprived of a vital energy source.

It’s made in the pancreas by combining the precursor molecule pro-insulin with zinc and calcium.

How does insulin work?

One of the primary functions of insulin is to facilitate the uptake of glucose by tissues from the bloodstream.

When insulin binds to specialised insulin receptors on the surface membrane of cells, glucose transporter proteins (glucose channels in the diagram below) fuse with the membrane, allowing glucose to enter. The most abundant of these transporter proteins in muscle and fat tissue is GLUT4.

Insulin function and blood glucose levels

Blood glucose levels may become elevated as a result of two main issues with insulin function:

  • Insulin deficiency – low production of insulin.
  • Insulin resistance – tissues not responding to the effects of insulin.

In both cases, glucose remains circulating in the bloodstream rather than taken up by tissue. This has several negative health effects and may be a sign of developing metabolic diseases, such as Type 2 diabetes.

Consequences of high fasting glucose

Fasting blood glucose levels refer to your level of blood glucose after you have had nothing to eat or drink after at least 8 hours. A normal fasting blood glucose level is between 70 mg/dL (3.9 mmol/L) and 100 mg/dL (5.6 mmol/L).

Impaired insulin function can result in high fasting blood glucose levels. This is associated with several negative health effects, including:


Cell damage

High amounts of glucose in the bloodstream can bind to molecules in cells through a process known as glycation. Glycation can directly impair the function of cells, but also leads to the formation of other harmful molecules called Advanced Glycation End Products (AGEs), which can damage blood vessels, nerves and organs. AGEs can therefore increase the risk of cardiovascular diseases, such as heart attacks and strokes.


Metabolic disease

Insulin resistance may cause the pancreas to produce significantly high amounts of insulin to compensate for its reduced effects. The pancreas may eventually become unable to keep up with the body’s demand for insulin, leading to the development of Type II diabetes and metabolic syndrome.


Impaired exercise performance

If glucose cannot enter muscle cells due to insulin dysfunction, less energy will be available for muscle contraction. As a result, this may lead to reduced exercise performance, as well as general tiredness and lethargy.

Your 'Fasting blood glucose' trait

To make a prediction of your fasting blood glucose levels, FitnessGenes analyze several of your gene variants (including those listed below) and relevant lifestyle factors using our innovative TrueTrait algorithm. 

These include:

Gene variants


This gene encodes a transporter protein which moves zinc during the formation of insulin. Variants of SLC30A8 influence how effectively you form and secrete insulin.



This gene encodes a protein which is activated when insulin binds to an insulin receptor. Variants of TCF7L2 affect your tissues sensitivity to insulin.



The coordination of our insulin release with the day/night cycle is strongly regulated by the ‘sleep hormone’ melatonin. Melatonin exerts its effects by binding to the melatonin receptor, which is coded for by the MTNR1B gene. Studies suggest that one variant of this gene causes people to produce less insulin during the night, resulting in increased blood glucose levels at this time.

Lifestyle factors

-Body composition

Excessive body fat and higher body fat percentage are associated with poorer insulin sensitivity, whereas greater lean body mass is linked to better control of blood glucose levels.


-Physical activity

Physical activity increases insulin sensitivity and improves blood glucose levels, partly through increased production of the GLUT4 transporter protein.



A diet high in saturated fat, trans fats and refined, high-GI carbohydrates is linked to the development of insulin resistance and high fasting blood sugar levels.



Disturbed sleep patterns can increase the risk of higher fasting blood glucose levels through resulting hormonal and behavioural changes, such as binge eating in response to sleep deprivation.

Depending on your combination of these genetic and lifestyle factors, you will be categorised into one of sixteen individual trait bands, ranging from ‘good’ fasting blood glucose levels to ‘very high glucose and insulin dysfunction risk’.

For those with high or very high predicted fasting blood glucose levels, replacing high Glycaemic Index (GI) carbohydrates with insoluble fibre, increasing sleep quality and drinking green tea may be included in recommended actions.


Discover your personal trait

Discover your personal fasting blood glucose level, alongside 70+ more traits, by unlocking your unique genetic code with the FitnessGenes.

Already have genetic data from providers including 23andMe or Receive same-day access to all traits with the FitnessGenes DNA Upload.

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Use our Plan Advisor to determine which genetically tailored diet and exercise program best fits your needs.

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