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The Prediabetes Nutritionist

Tell-Tale Signs You Should Screen for Prediabetes

Family history of diabetes, high-risk ethnicity or overweight? This post details the tell-tale signs you screen for prediabetes.

Recent statistics from the International Diabetes Federation show that almost 240 million adults worldwide are unaware they live with diabetes. Notably, 75% of these adults reside in low- and middle-income countries where access to healthcare and preventive strategies may be poor (IDF, 2021). Only 15.3% of people with prediabetes are aware they live with the condition in the US.  

Diabetes is a very serious condition. And although many people underestimate its severity, it’s the leading cause of kidney failure and new cases of blindness among adults in the United States (Duan et al., 2021). Even if you don’t have symptoms, screening for prediabetes and type 2 diabetes is crucial because you can spot and treat them early and avoid life-threatening complications, improving your health outcomes. 

This post details who should screen, when to screen and the tell-tale signs indicating you may already have diabetes. 

What is screening, and why is it done?

Testing and screening for diabetes are two separate entities. When a person shows symptoms, diagnostic tests confirm they have the condition; these tests do not represent screening (ADA, 2021). 

Screening is done to identify people without signs or symptoms who are likely to have diabetes. It is done because diabetes is a significant burden to healthcare systems worldwide. Since the disease is well-understood, it can be diagnosed early. And with evidence-based measures, healthcare professionals can work with individuals to prevent progression from prediabetes to type 2 diabetes, put type 2 diabetes into remission and delay or prevent life-threatening complications (ADA, 2002).  

Who should screen for prediabetes?

Prediabetes doesn’t happen overnight; it slowly develops over up to ten years and then takes up to seven years before progressing to type 2 diabetes (Bertram and Vos, 2010). And while it rarely causes symptoms, prediabetes is not harmless. The insulin resistance and high blood sugar typical of prediabetes can damage the heart, nerves, kidneys, limbs, and eyes (Wasserman, Wang & Brown, 2018). 

Studies show that approximately 11-25% of individuals with prediabetes have signs of nerve damage, while others present with heart disease and erectile dysfunction (Lin et al., 2020; Jin et al., 2022). But the great news is that frequent screening, especially of people with a high risk of diabetes, allows for early detection and significantly reduced rates of damage to these organs (Duan et al., 2021). 

Who has a high risk of diabetes?

Caucasians over the age of 40, with overweight – defined as a body mass index (BMI) above 25 kg/m2 or obese – a BMI above 30 kg/m– have a high risk of diabetes. However, for non-Caucasians, people younger than 40 with obesity, overweight, and even healthy BMIs are at risk of diabetes. 

Current National Institute for Health and Care Excellence (NICE) guidelines recommend that all adults (except pregnant women) aged above 40 be screened for diabetes. However, people of South Asian, Chinese, African-Caribbean, Black African and other high-risk black and minority groups, except pregnant women, should be screened from age 25. 

The American Diabetes Association (ADA) guidelines recommend that screening for diabetes should begin at age 35 for all US adults but at age 25 for non-Caucasians with overweight or obesity and other risk factors (ADA, 2022). However, a new study by a team of American scientists published in Annals of Internal Medicine has found that these screening criteria may miss many non-Caucasians with diabetes, leading to a delay in diagnosis and severe complications. 

“We found that a more equitable approach would be to offer screening starting at a BMI of 20 kg/mto Asian Americans ages 35 to 70, and at 18.5 kg/m2 in Hispanic and Black Americans in this age group,” Rahul Aggarwal, MD, first author of the study and an internal medicine resident at BIDMC said in a press release

“We also found that among individuals from racial and ethnic minority populations with overweight or obesity, it would be equitable to offer diabetes screening starting in the early 20s rather than waiting till they are 35 years old. Delayed diagnosis and inadequate treatment of diabetes can produce catastrophic consequences, jeopardising one’s heart, kidneys, eyes, and limbs,” Aggarwal added. 

Besides age and ethnicity, other factors that indicate a person has a high risk of diabetes and should screen for diabetes include:

  • A family history of diabetes
  • High Waist circumference (greater than 80cm in women and greater than 94cm in men)
  • High blood pressure
  • History of cardiovascular disease
  • Raised triglycerides and/ or low HDL cholesterol
  • A history of gestational diabetes
  • Polycystic Ovary Syndrome
  • Acanthosis nigricans
  • Non-alcoholic fatty liver disease
  • Medications (glucocorticoids, thiazide diuretics, antipsychotics & HIV mediation)

What does prediabetes screening involve?

Screening is done in two stages: first, completing a validated questionnaire and, depending on the results, undergoing diagnostic tests (NICE, 2012; ADA, 2002). 

Validated questionnaires typically inquire about your age, gender, ethnicity, family history, waist measurement, body mass index and blood pressure. The questionnaires award points based on your answers and sums them to determine if you have a low, moderate, or high risk of developing type 2 diabetes. You can self-assess using the Diabetes UK Know Your Risk tool. You will be referred to your GP if you live in the UK and are considered high-risk. You can self-assess with the ADA risk test or the IDF test2prevent risk assessment if you live outside the UK

Your doctor will check your blood sugar levels either with a glycated haemoglobin (HbA1c), fasting blood glucose or oral glucose tolerance test (OGTT) if you are considered high risk. 

The HbA1c test measures your average blood glucose levels over the preceding three months. It is the most straightforward test because it doesn’t require overnight fasting. However, it is unsuitable for people with blood disorders such as sickle cell anaemia or thalassemia and those with kidney disease. In the US, an HbA1c of 5.7-6.4% (39-47 mmol/l) is defined as prediabetes, but it is defined as 6.1-6.4% (42-48 mmol/l) in the UK. An HbA1c over 6.5% is considered diabetes in both countries. 

The fasting blood glucose measures your blood glucose levels after at least eight hours without food or drink. The ADA considers it the best screening test for diabetes, but the World Health Organisation (WHO) believes it misses around 30% of people with undiagnosed diabetes (ADA, 2002; WHO, 2006). In the US, fasting blood glucose of 100-125 mg/dL (5.6-6.9 mmol/L) is considered prediabetes, but in the UK, it is 110-125 mg/dL (6.1-6.9 mmol/L). Fasting blood glucose over 126 mg/dL (>7.0 mmol/L) is considered diabetes.  

The OGTT is arguably the most unpleasant and time-consuming test. You must fast overnight, consume a drink containing 75g of glucose and then have a blood test two hours later. The test determines whether your body processes glucose correctly after eating—the WHO considers the OGTT the most reliable for detecting prediabetes and type 2 diabetes. An OGTT of 140-199 mg/dL (7.8-11.0 mmol/L) is prediabetes, while >200 mg/dL (11.1 mmol/L) is diabetes.

How often should you screen?

If the screening shows you have a low risk, you should continue to screen every three years. Screening this frequently ensures that false negatives are detected early and reduces the odds of an undiagnosed individual developing significant complications before detection. If you have one or more of the risk factors mentioned above, you may need to screen more frequently. 

Signs you may already have diabetes

Prediabetes has progressed to type 2 diabetes before being detected in many cases. Notably, newly diagnosed individuals with diabetes have already lost 50% of their beta (insulin-producing) cell function before diabetes symptoms manifest. 

You may already have diabetes if you are high-risk and have one or more of the following symptoms: 

  • Excessive thirst
  • Frequent urinating, especially at night
  • Unintentional weight loss
  • Constant hunger
  • Feeling very tired
  • Cuts or wounds that take longer to heal
  • Itching around the genitals
  • Blurred vision

Now you know why screening for diabetes is essential, what it entails and whether you should undergo screening. 

Remember that feeling well doesn’t exempt you from diabetes screening, particularly if you’re considered high risk. Early detection allows you to reverse prediabetes or put type 2 into remission, dramatically improving your health outcomes.  

If you, a friend, or a family member is at risk of diabetes, please encourage each other to complete the free screen. It is free and takes less than two minutes of your time. 


  1. International Diabetes Federation (2021) Diabetes facts and figures. Available: Accessed: 16 May 2022
  2. Duan, D., Kenge, A.P., & Echouffo-Tcheugui, J.B. (2021) Screening for diabetes and prediabetes. Endocrinology and Metabolism Clinics of North America, 50: 369-385
  3. Betram, M.Y & Vos, T. (2010) Quantifying the duration of prediabetes. Australian and New Zealand Journal of Public Health, 34(3): 311-4. 
  4. Lin, Y-C., Lin, C. S-Y., Chang, T-S., Lee, J-E., Tani, J., Chen, H-J., & Sung, J-Y. (2020) Early sensory neurophysiological changes in prediabetes. Journal of Diabetes Investigation, 11(2); 458-465. 
  5. Jin, M., Yuan, S., Wang, B., Yi, L & Wang, C. (2022) Association between prediabetes and erectile dysfunction: a meta-analysis. Frontiers in Endocrinology
  6. Wasserman, D.H., Wang, T.J., & Brown, N.J. (2018) The vasculature in prediabetes. Circulation Research, 122 (8): 1135-1150.
  7. Brannick, B., Wynn, A., & Dagogo-Jack, S. (2016) Prediabetes as a toxic environment for the initiation of microvascular and macrovascular complications. Experimental Biology and Medicine, 241 (12): 1323-1331. 
  8. World Health Organisation (2006) Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia. Available: Accessed: 16 May 2022
  9. US Preventive Services Task Force (2021) Screening for prediabetes and type 2 diabetes. US Preventive Service Task Force recommendation statement. JAMA, 236(8): 736-743
  10. National Institute for Health and Care Excellence (2012) Type 2 diabetes: prevention in people at high risk [PH38] Available: Accessed: 17 May 2022. 
  11. American Diabetes Association (2002) Screening for diabetes. Available: Last accessed: 17 May 2022. 

DISCLAIMER: Not a substitute for medical advice – All content is for informational purposes only and is not intended to provide medical or nutrition advice or to take the place of medical/nutrition advice or treatment from your doctor or health professional. Since each person’s health conditions are very specific, viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. All content, including text, graphics, images, and information, contained in this post/video is for general information purposes only and does not replace a consultation with your own doctor/health professional.

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