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The Prediabetes Nutritionist

Prediabetes: Causes, Warning Signs and Risk Factors

Has your doctor recently told you that you have ‘a touch of sugar’ or ‘borderline diabetes’, and you’re unsure what it means? 

A touch of sugar and borderline diabetes are phrases used to describe prediabetes. While these phrases try to alert people that their blood glucose control is impaired, they don’t effectively communicate the severity of the condition. 

This article explains in simple terms what prediabetes is, its causes, signs and symptoms and the complications that may occur without proper control. 

Keep reading to learn more. 

What is Prediabetes?

When your body processes food correctly, your blood glucose is maintained with a narrow range from a low of about 70 mg/dL (3.9 mmol/L) when you’re fasting to a high of about 139 mg/dL (7.7 mmol/L) two hours after eating. 

Prediabetes occurs when blood sugar levels are higher than usual but not high enough to be in the diabetic range. In medical terms, a person has prediabetes if they have higher than usual:

  • Fasting blood glucose 
  • Blood glucose two hours after eating 
  • Glycated haemoglobin (HbA1c) – indicates the average blood glucose over the last two to three months.

How is Prediabetes Diagnosed?

Prediabetes is diagnosed with blood glucose tests that measure blood glucose after at least eight hours without food (fasting blood glucose), two hours after taking 75g of glucose (oral glucose tolerance test) or over the last two to three months (HbA1c). 

There is still no general agreement on the best test to diagnose prediabetes because each test has pros and cons. 

According to the World Health Organisation (WHO), measuring fasting blood glucose tests alone misses around 30% of people with diabetes, and some individuals may find it challenging to go without food for eight hours before taking the test. 

The oral glucose tolerance test is the only test that identifies abnormal blood glucose levels after eating. However, it doesn’t always produce consistent results, is expensive, and many people find it unpleasant. 

The HbA1c test is the easiest to perform because it can be done at any time and doesn’t require any special preparation such as fasting. However, it is scarce in many countries worldwide and challenging to standardize. And because it measures the average blood glucose over the preceding two to three months, HbA1c testing is unsuitable for people with anaemia, blood disorders such as sickle cell or thalassaemia, pregnancy, or kidney disease. 

Because of these reasons, the WHO doesn’t consider the HbA1c test suitable to diagnose prediabetes or diabetes. However, many countries with access to the test use it frequently. 

The WHO and American Diabetes Association (ADA) use different fasting glucose and HbA1c ranges to define prediabetes, with the ADA using a wider range than the WHO. The table below outlines the ranges for normal blood glucose, prediabetes, and diabetes. 

Glucose Ranges for People with Prediabetes and Diabetes 
TestNormalPrediabetes (ADA)Prediabetes (WHO)Diabetes
Fasting blood glucoseLess than 5.5 mmol/L (100 mg/dL)5.6-6.9 mmol/L (100-125 mg/dL)6.1-6.9 mmol/L(110-125 mg/dL)At least 7.0 mmol/L (≥126 mg/dL)
Blood glucose two hours after eatingLess than 7.8 mmol/L (140mg/dL)7.8-11.0 mmol/L (140-199 mg/dL)7.8-11.0 mmol/L (140-199 mg/dL)At least 11.1 mmol/L (≥200 mg/dL)
HbA1cLess than 42 mmol/L(<6%)39-47 mmol/L (5.7%-6.4%)42-47 mmol/L (6%-6.4%)At least 48 mmol/L(≥ 6.5%)

What is the Prevalence of Prediabetes in Nigeria, the United Kingdom, and the United States?

The prevalence of prediabetes in Nigeria is 15.8 million according to the ADA criteria and 10.4 million according to the WHO criteria (Bashir et al., 2021). Prediabetes affects women and men at a similar rate of 12.1%, and the rates are also similar in urban and rural areas at 9%. 

Based on ADA cut-offs, a 2014 study found that 35.3% of adults in the United Kingdom (UK) have prediabetes (Mainous et al., 2014). And while there was no significant difference in prediabetes rates between men and women, people of Black origin were the most affected.  

In the United States, an estimated 88 million or 34.5% of all adults have prediabetes based on their fasting glucose or HbA1c level (Centres for Disease Control, 2020). Prediabetes is more common in men than women, 37.4% vs. 29.2%, respectively, but similar across all ethnic groups and education levels. 

What Causes Prediabetes

Prediabetes is caused by defects in insulin action and production.

There are irregularly shaped tissues within the pancreas called the Islet of Langerhans. These tissues contain alpha cells that produce the hormone glucagon and beta cells that produce insulin.

Insulin and glucagon work together to control blood sugar, but since defects in insulin production and action usually cause prediabetes, this section will focus on insulin.

Insulin regulates blood sugar by instructing the cells in the body to absorb glucose from the bloodstream after a meal. If there’s excess glucose, insulin stimulates the liver and muscles to store it as glycogen or the fat tissue to store it as fat.

Prediabetes occurs when your body begins to lose control of glucose. Two main factors contribute to this loss of control:

  • The beta cells in the pancreas stop producing enough insulin
  • The liver, muscles and fat tissues stop being sensitive or responding to insulin

Now you may be asking, why do the beta cells stop producing enough insulin, and why do the liver, muscles and fat stop responding to insulin?

When a person eats excess fat, protein and carbohydrates for prolonged periods, the pancreas must produce insulin continuously to remove them from the bloodstream and store them adequately. 

Continuous insulin production puts enormous stress on the pancreas, which gradually loses its ability to produce enough insulin. At the same time, the liver, fat cells and muscles stop responding to insulin correctly – a condition called insulin resistance. 

Note that Insulin typically stimulates the liver to store excess glucose as glycogen or fat. But if the beta cells cannot produce insulin or the liver cells can’t respond to insulin, excess glucose remains in the bloodstream. As glucose in the blood rises above normal levels, prediabetes results. 

What are the warning signs and symptoms of prediabetes?

Prediabetes is often present without warning signs and symptoms. Signs and symptoms may indicate progression to type 2 diabetes and may include:

  • Frequent urination (especially at night) and thirst because the glucose in the urine pulls water out of your body and fills your bladder, making you want to urinate more often. As you lose water, you get thirsty, and the cycle repeats. 
  • Fatigue because the cells are not getting the energy they need to carry out their usual functions.
  • Frequent vaginal infections in women because glucose spills into the vaginal tissues. Yeast naturally present in the vagina thrives on sugar, causing itching, burning and abnormal discharge, often with an odour.
  • Cuts and wounds that heal very slowly
  • Blurred vision
  • Increased hunger

What factors increase the risk of prediabetes?

1 | Age – The risk of prediabetes increases with age, with those above 40 years at the greatest risk. However, the risk of prediabetes increases from age 25 in people of Black, South Asian, and Hispanic descent. 

2 | Family history/genetics – People with a family history of diabetes (parent, sibling, or child) have a two to a six-fold higher risk of prediabetes. Other genetic medical conditions such as polycystic ovary syndrome and Mendenhall syndrome also increase risk. 

3 | Ethnicity – People of Black and South Asian descent have a two to a four-fold higher risk of developing type 2 diabetes than other races.  

4 | Biological Sex – Men have a higher risk of prediabetes than women, possibly because they store more fat around their organs. 

5 | Diet – The types of food you eat significantly affect prediabetes risk. Consuming excessive calories, mainly from ultra-processed high-fat and high-sugar foods is linked to a higher risk of prediabetes. 

6 | Physical activity – physical inactivity and sedentary behaviours, such as prolonged screen time, is leading risk factor for prediabetes. Physical inactivity promotes insulin resistance and increases the risk of progression from prediabetes to type 2 diabetes. 

7 | Obesity – excessive body fat is the most significant risk factor for prediabetes and progression to type 2 diabetes. It is worth noting that diabetes risk is also high in people with a healthy weight but high-fat levels around their organs.

8 | Sleep – Poor sleep quality and quantity affect how the body processes glucose, increasing prediabetes risk. Poor sleep can also increase stress, which in turn causes blood sugar imbalances.

9 | Smoking – Studies show that smokers have a higher risk of developing prediabetes and type 2 diabetes than non-smokers, with heavier smokers displaying a higher risk than lighter smokers. The exact pathway by which smoking increases prediabetes risk is unclear, but it may be through fat gain.

In summary, prediabetes occurs because of insulin resistance and impaired insulin production.

Although you cannot change some risk factors such as genetics and age, others can be modified, including obesity, physical inactivity, smoking, and poor eating habits. 

If you’ve recently been diagnosed with prediabetes, there is good news! You can put it into remission or reverse it by improving your eating habits and moving more. 

And remember, you don’t need to make sweeping changes overnight. Focus on changing one thing at a time. You’re more likely to stick to those changes and cultivate a healthy lifestyle over time.

You can do this!


  1. Bansal, N (2015) Prediabetes diagnosis and treatment: a review. World Journal of Diabetes; 6(2): 296-303.
  2. Tabak, A.G., Herder, C., Rathman, W., Brunner, E.J., & Kivimaki, M. (2012) Prediabetes: A high-risk state for developing diabetes. Lancet, 379 (9833): 2279-2290. 
  3. Mainous, A.G., Tanner, R.J., Baker, R., Zayas, C.E., & Harle, C.A. (2014) Prevalence of prediabetes in England from 2003 to 2011: population-based, cross-sectional study. BMJ Open, 4(6):e005002. 
  4. Bashir, M.A., Yahaya, A.I., Muhammad, M., Yusuf, A.H & Mukhtar, I.G. (2021) Prediabetes burden in Nigeria: a systematic review and meta-analysis. Frontiers in Public Health, 9: 762429
  5. Centres for Disease Control and Prevention. National Diabetes Statistics Report, 2020. Accessed February 03, 2022. Available from:
  6. World Health Organisation (2011) Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. Accessed: February 03 2022. Available from:
  7. World Health Organisation (2006) Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia. Accessed: February 03 2022. Available from:
  8. Ley, S.H>, Schulze, M.B., Hivert, M-F., Meigs, J.B., & Hu, F.B. Risk factors for type 2 diabetes In: Diabetes in America. 3rd Edition. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases (US); 2018. Aug. Chapter 13. Available from:

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