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High Blood Sugar: Everything You Need To Know! 

With worldwide figures of obesity and obesity-related disease reaching record highs, it’s never been more important to understand blood sugar and how it relates to health and disease. Chronic high blood sugar is the defining feature of type 2 diabetes, and a known cause of other chronic conditions including heart disease and some forms of cancer. Whilst there are some unavoidable risk factors for such conditions, there are also a number of factors which can be managed, such as diet and lifestyle.

Homeostasis Symptoms Measuring Prevention


  • High blood glucose is linked with multiple chronic health conditions, including cancer and Alzheimer’s.
  • Everybody responds differently to individual foods.
  • Blood sugar can be measured in different ways, and also now in real-time using a continuous glucose monitor.


Key to understanding blood sugar regulation is the concept of homeostasis. Homeostasis is a key tenet of physiology and medicine. It refers to the body’s ability to regulate its environment and sustain internal conditions that allow for life and health. Levels of oxygen, glucose, and electrolytes in your blood are just some examples of factors that require homeostasis. It occurs from the moment life begins via a dynamic process involving complex, intertwined networks of feedback loops. This allows us to maintain more or less constant internal conditions, adapting in order to survive, through constant changes in the environment.   

Conversely, poor health and disease is more often than not caused by a disruption in homeostasis. And effective treatment of disease is often centred around correcting and re-establishing homeostatic conditions in the body. This was recognised as far back as Hippocrates who said vis medicatrix naturae referring to the body’s incredible capacity to maintain health and balance. In light of this fact, it was traditionally a physician’s role to clear the path to homeostasis to allow nature to take its course.  

So what does this have to do with blood sugar? 

Sugar, broken down into glucose from carbohydrates in the diet, is the main source of energy for cells in our body. It is transported around the body in our blood but cannot be stored safely there. Instead, when sugar is not used immediately for energy, it is delivered into the liver and muscles to be stored, and then released as needed. This allows blood sugar levels to be kept within a very narrow range of about 4-6mmol. This occurs mainly through the action of pancreatic hormones, insulin and glucagon, which facilitate the transit of glucose to and from the blood. This is blood sugar or glucose homeostasis.

Blood Sugar Homeostasis Disruption 

When glucose homeostasis is disrupted, it leads to either high or low blood sugar, both of which have various symptoms which you can look out for (see below).  In the short term, the body is able to cope with these fluctuations, releasing more and more insulin or glucagon to keep blood sugar levels balanced, but over time can cause serious problems in the body.  

 By far the most common disruption to blood glucose is high blood sugar or hyperglycaemia. Chronic high blood sugar is known as type 2 diabetes and is caused by a progressive loss of sensitivity to insulin. In the early stages of type 2 diabetes, homeostasis is maintained through the production of increasingly more insulin. But eventually, this process becomes exhausted resulting in persistent high blood sugar or type 2 diabetes.  

 As we’ve said, the maintenance of homeostasis in the body relies on a highly complex and interlinked network of systems, all of which impact one another. So, when glucose homeostasis is lost, there is a predictable knock-on effect. One of these is an increase in reactive oxygen species or ‘free radicals’ in the body. Free radicals are particles in the blood and body tissue which are produced as by-products of normal body functions such as respiration and immune defence. They also come from external sources such as smoking, alcohol, and chemicals in the environment. In normal circumstances, free radicals are kept under control by a system of antioxidants; this is like an army of peacekeepers that patrol the body, neutralising harmful free radicals and preventing them from causing damage. However, just as high blood sugar can overwhelm the body’s ability to maintain glucose homeostasis, increasing numbers of free radicals in the body can overwhelm the antioxidant defence system. This leads to a situation known as oxidative stress which in turn contributes to many of the complications of type 2 diabetes including kidney disease, nerve damage, decline in eyesight, and vascular damage. 

 So, how do I know if I might have high blood sugar? 

What are the symptoms of high blood sugar?

Unfortunately, the symptoms of high blood sugar tend to come on gradually and may only be noticeable when your blood sugar levels become very high. 

The symptoms of high blood sugar include:  

  • feeling very thirsty
  • peeing a lot  
  • feeling weak or tired  
  • blurred vision
  • losing weight
  • repeated infections including urine and skin infections e.g. thrush 

 Fortunately, there are many ways of testing your blood sugar which can be used to pick up on any signs that homeostasis is under threat.  

Ways of measuring blood sugar

Fasting Blood Glucose (FBG) 

This test measures blood sugar after an 8-12 hour fast. An FBG of over 7 mmol/L indicates diabetes, and the upper limit of ‘normal’ is 5.6 mmol/L. Any value between 5.6 and 6.9 mmol/L is considered prediabetes.

A limitation of this test is that it does not tell us how blood sugar responds to the food we eat.

Oral Glucose Tolerance Test (OGTT) 

This test, normally performed during pregnancy, involves drinking 75g of pure glucose dissolved in water and then measuring blood glucose beforehand and then again two hours later. If your blood sugar is higher than 11.1 mmol/L two hours later, you may have type 2 diabetes, or gestational diabetes if pregnant. A result between 7.8 and 11 mmol/L suggests impaired glucose tolerance.

A limitation of the OGTT is that the large dose of sugar consumed can cause severe symptoms in people with impaired glucose tolerance. Furthermore, the sugar in food does not generally occur in the glucose form used in this test. This means the test isn’t an accurate representation of how the body responds to carbohydrates in the diet. 

Haemoglobin A1c (HbA1c) 

This test reflects average blood sugar over the past three months by measuring the percentage of haemoglobin to which sugar has bonded to. Prediabetes is diagnosed at a level of 42 to 47 mmol/mol (6 to 6.4%) and diabetes is diagnosed at 48mmol/mol and above (6.5% and above). HbA1c is generally recognised as the gold standard for type 2 diabetes diagnosis but can be unreliable.  

Continuous Glucose Monitoring (CGM) 

CGM is the continuous monitoring of glucose throughout the day and night via a tiny sensor usually on your arm or tummy. This sensor tests your interstitial glucose level, which is the glucose found in fluid between the cells, every few minutes and wirelessly transmits the information to a monitor- usually an app on your phone.  

CGMs are always on and recording glucose levels which can be extremely helpful in recognising patterns in your blood sugar levels, and understanding how different foods and lifestyle factors affect you. You can also set an alarm to alert you to blood sugar levels going too high or too low. 

What causes high blood sugar and type 2 diabetes? 

Over the years there have been many suspected primary causes of type 2 diabetes such as dietary fat, sugar, and being overweight. However, it is now understood that there is no single factor that results in type 2 diabetes. It has become clear that the disease is driven by a complicated milieu of diet, lifestyle, oxidative stress, and genetics.  

Without a doubt, the Western diet, high in industrially processed foods, chemicals, and sugar is a well-known risk factor for type 2 diabetes. As industrialisation and the features of this diet have spread through worldwide populations, so has type 2 diabetes and all of the problems that go with it.  

Poor sleep, a sedentary lifestyle, chronic stress, environmental toxins, and poor gut health are also known to play significant roles in the development of type 2 diabetes. These factors contribute to the unraveling of homeostasis in the body leading to oxidative stress, damage to the pancreas (responsible for producing insulin), and progressive insulin resistance. This sets the stage for serious metabolic dysfunction and an increasingly high risk of metabolic syndrome and disease.  

How can I prevent high blood sugar? 

Whilst there are some risk factors for type 2 diabetes that can’t be avoided such as genetics and some environmental factors, there is a lot you can do to reduce your risk by understanding what makes the differences to you as an individual.  

In a recent blog, we discuss some of the top foods for balancing blood sugar and losing weight.

Avoiding long periods of sitting down each day and doing at least 150 minutes of moderate exercise each week is known to reduce your risk of metabolic disease. Similarly, getting enough good quality sleep (7-9 hours a day) is vital for maintaining a healthy weight and helps you to sustain an active and healthy lifestyle.  

At NUVI, we provide comprehensive guidance and support to help you to understand and more accurately reduce your risk of high blood sugar and metabolic disease. 

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