Prediabetes: what you need to know

Dr Angela Murphy goes into detail about prediabetes and highlights that healthcare providers need to provide specific, useful information to stop the progression.

Mrs T, a 65-year-old lady, has just been told she has prediabetes. She relays this information to her daughter describing it as ‘a touch’ of diabetes. She has been told that she must just avoid sugar and she will be fine. Her daughter, however, wants to know more and asks the following questions:

What is prediabetes?

Prediabetes includes the conditions: impaired fasting glucose and impaired glucose tolerance. These describe levels of blood glucose that are higher than normal but not yet in the diabetic range. These higher glucose levels are associated with a significantly higher risk of developing cardiovascular disease as well as progression to diabetes.

How is prediabetes diagnosed?

There are international guidelines set out to diagnose diabetes and prediabetes. Over the last decades, the goal posts have been moved several times in the diagnosis of prediabetes.

Blood glucose levels are measured fasting after eight hours of no food or drink, or two hours after a glucose challenge. This is given as a drink containing 75g of glucose. Your healthcare provider will ask the laboratory to do an oral glucose tolerance test (OGTT). This is the only test that can diagnose impaired glucose tolerance and is considered a sensitive test to diagnose prediabetes.

To definitively diagnose prediabetes, two tests should be done on separate days.

Table 1 shows the glucose levels for normal, prediabetes and diabetes.


FASTING GLUCOSE (mmol/L) ≤ 6,0 6,1-6,9 ≥ 7,0
2-HOUR GLUCOSE*(mmol/L) <7,8 7,8-11,0 ≥ 11,1
HBA1C % ** ≥ 6,5

*2-hour glucose level after a 75g glucose challenge

**HbA1c is not used in the categorization of prediabetes

Where: Fasting is defined as no caloric intake for 8 hours

2-hour glucose is measured after a 75g glucose load given in 250ml of water over five minutes.

What are the symptoms of prediabetes?

It’s unlikely that a person will have any specific symptoms of prediabetes. As glucose rises, thirst and loss of weight may occur. It’s concerning that in many instances prediabetes is detected when tests are done to investigate another complaint, particularly ones that may be a complication of diabetes such as the following:

 Peripheral neuropathy – damage to the small nerves of the feet cause pain and discomfort which may be described as burning, pins and needles, or sensitive. This may eventually lead to complete loss of sensation.

Cardiovascular disease – cardiac disease such as angina, heart attack or heart failure; peripheral vascular disease resulting in decreased blood flow in the legs causing pain on walking; stroke or transient ischaemic attack.

Kidney disease – this would be detected with blood and/or urine tests.

Other described complications of diabetes may be a presenting feature of prediabetes, but these are infrequent, e.g. retinopathy, autonomic nervous dysfunction (including impotence in men) and poor wound healing or recurrent infections.

Who should be tested for prediabetes?

Increased body weight is the greatest risk for developing prediabetes. It’s also more frequent in older populations and those with a family history of diabetes. Certain ethnicities have a higher incidence and in South Africa, our Indian community has a particular increased risk. Women with a history of gestational diabetes (diabetes developed during pregnancy) and polycystic ovarian syndrome may develop prediabetes or diabetes as well.

When should people be tested for prediabetes?

The US Preventative Task Force recommends screening for prediabetes every three years in adults with normal blood glucose, especially if they have risk factors.

Our South African guidelines suggest that all adults be screened for high glucose from the age of 45 years but an adult who is overweight can be screened at any age. The frequency of repeat screening will depend on the presence of the risk factors mentioned above.

Can prediabetes be treated?

Several large studies have shown conclusively that it’s possible to prevent the progression of prediabetes to diabetes. In the Finnish Diabetes Prevention Study (DPS) and the Chinese Da Qing Study, weight loss and physical exercise showed significant benefit.

The DPS demonstrated a 58% relative risk reduction in the progression to Type 2 diabetes in participants with impaired glucose tolerance who were treated with intensive lifestyle modification. The Da Qing study showed a similar 51% lower incidence of progression to Type 2 diabetes in a similar population of prediabetes.

Most importantly, there was still a 43% lower incidence seen over a 20-year follow-up period and this was associated with overall lower mortality. It’s incredible to think that a six-year lifestyle intervention showed such long-term benefits.

Other trials have shown benefit with pharmacological treatment. The most quoted of these is the Diabetes Prevention Programme undertaken in the US. Lifestyle intervention alone was compared to metformin, a medication that is the cornerstone of Type 2 diabetes management. The group following lifestyle alone showed a 58% decrease in the incidence of Type 2 diabetes compared with 31% in the metformin group.

The Diabetes Prevention Programme Outcomes Study followed up these subjects for a mean of 15 years offering twice yearly lifestyle reinforcement to the lifestyle group and ongoing metformin to the second group. Type 2 diabetes incidence was further reduced by 27%.

Other studies have looked at the role of diabetic medications to treat prediabetes and, thus, prevent progression to diabetes, e.g. pioglitazone, acarbose (no longer available in SA) and orlistat (a weight loss agent).

Should medications be used to treat prediabetes?

There is a role for medications, but several factors must be considered. All of these medications, including metformin, can have side effects. In addition, medical funders don’t recognise any prediabetes condition as a primary medical benefit so the medications can’t be put on to chronic reimbursement.

For there to be ongoing benefit from the medications, they do need to be continued. It’s recommended that medications be considered in people who haven’t reversed their prediabetes diagnosis with lifestyle alone or in individuals who are considered very high risk of progressing to diabetes.

According to our local South African guidelines these would include people with the following:

  • Age < 60 years old
  • A history of gestational diabetes
  • A BMI > 35 kg/m2
  • Presence of both impaired fasting glucose and impaired glucose tolerance
  • The metabolic syndrome (hypertension, high cholesterol, obesity)

The treatment of choice is metformin starting at a dose of 500mg twice daily, but this can be adjusted if glucose levels don’t improve.  Repeat blood tests can be done every three to six months. The person will need to be advised that this medication is being used off-label.

Orlistat is an option for those people struggling to lose weight as it has shown benefit for both weight reduction and glucose lowering.  However, it has significant gastrointestinal side effects requiring an almost fat-free diet which is not suitable for everyone.

What lifestyle intervention is best for prediabetes?

Weight loss

The key elements of lifestyle intervention are a reduction in body weight and an improvement in physical activity. Data from the DPP showed that for every 1kg of weight lost, there was a 16% decrease in the risk of developing Type 2 diabetes. Referring patients to a registered dietitian to embark on this journey is best. Weight loss requires significant calorie reduction, and it’s essential for a balance of nutrients to be included in the diet.

For patients who struggle to achieve significant weight loss, it’s reasonable to discuss weight loss medications, such as orlistat mentioned above, or liraglutide, now available in SA.As a rule of thumb there should be 5% weight loss in three months. If that isn’t attained, then the method of weight loss has to be discussed with the dietitian or the doctor.


Physical activity needs to be of a moderate intensity, such as brisk walking, and it needs to be regular. A daily 30-minute session five days a week is ideal. The aim is usually to be active for 150 minutes per week which burns around 700 kilocalories.

Where possible, it’s best to have a mixed exercise programme that includes resistance training, stretching and cardiovascular. Light weight training improves insulin resistance and, thus, blood glucose levels.

It’s important to be active during the day, choose the stairs and not the lift, park far from the shop entrance but these types of activities can’t be counted as part of the 150 minutes.

Support system

If it was easy, we would all be losing weight and exercising regularly.  The reality is that for many people, achieving these goals is a struggle so a support system must be in place. It can be difficult to motivate yourself to go for a walk at the end of a busy workday, but if you have a friend or family member to motivate you and get you walking, it will help.

It’s encouraged to follow some structured programme, preferable with supervision. The COVID pandemic has presented a huge challenge with the closing of exercise classes, gyms and even the popular parkrun. Now that we are able to return to these activities, try and have a specific programme.

Seeing the dietitian regularly helps keep up the motivation to follow the eating plan. It’s important to set goals and to troubleshoot when the goals aren’t being met.


The importance of identifying prediabetes isn’t to diagnosis a stand-alone condition but rather to highlight the continuum of risk of increasing blood glucose levels to cardiovascular diseases and diabetes itself.

At the point of prediabetes, there is a definite window of opportunity to change lifestyle and improve blood glucose, to reverse the prediabetes and prevent the development of Type 2 diabetes.

Healthcare providers should provide specific, useful information for people to be able to make these changes and guidelines on the follow-up of blood glucose testing.


  1. US Preventive Services Task Force. Screening for Prediabetes and Type 2 Diabetes: US Preventive Services Task Force Recommendation Statement. 2021;326(8):736–743. doi:10.1001/jama.2021.1253
  2. Guideline Committee. The 2017 SEMDSA Guideline for the Management of Type 2 Diabetes. JEMSDA 2017; 22:1(Supplementary pgS1-S192)
  3. The Diabetes Prevention Program. Design and methods for a clinical trial in the prevention of type 2 diabetes. Diabetes Care. 1999 Apr; 22(4):623-34.
  4. Table Adapted from The 2017 SEMDSA Guideline for the Management of Type 2 Diabetes. JEMSDA 2017; 22:1(Supplementary pgS1-S192)


Dr Angela Murphy is a specialist physician working in the field of Diabetes and Endocrinology in Boksburg. She has a busy diabetes practice.

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