What it is

Prediabetes reflects early insulin resistance and/or an initial weakening of the pancreas's ability to produce insulin. The category covers two overlapping conditions: impaired fasting glucose and impaired glucose tolerance. The key practical difference between prediabetes and diabetes is reversibility — with enough attention to lifestyle, glucose levels can return to normal.

The levels used to define it

In the medical literature, prediabetes is described using the following approximate ranges (provided as reference information, not as instructions for self-diagnosis):

  • Fasting glucose: 100–125 mg/dL (5.6–6.9 mmol/L) under ADA criteria; the WHO uses a somewhat stricter range — 110–125 mg/dL (6.1–6.9 mmol/L);
  • Oral glucose tolerance test (2 hours after a 75 g glucose load): 140–199 mg/dL (7.8–11.0 mmol/L);
  • HbA1c (glycated hemoglobin): 5.7–6.4%.

By comparison, diabetes is generally diagnosed at a fasting glucose level ≥126 mg/dL (7.0 mmol/L) or an HbA1c ≥6.5%. For more on the diagnostic methods themselves, see the "Diagnosis" page.

How common it is

According to aggregated CDC data, more than a third of adults in the US have prediabetes, and about 8 in 10 of them aren't even aware of it. IDF-related estimates suggest around 720 million people worldwide had prediabetes in 2021, a figure that could approach 1 billion by 2045. These global estimates are less standardized than statistics for diabetes itself, so they should be treated as approximate.

Risk factors

  • excess weight or obesity, low physical activity;
  • a family history of diabetes, older age;
  • a history of gestational diabetes or giving birth to a baby weighing over ~4 kg (about 9 lb);
  • high blood pressure and abnormal lipid levels;
  • polycystic ovary syndrome (PCOS), acanthosis (darkened skin patches) as a marker of insulin resistance.

Symptoms

In most cases prediabetes has no symptoms at all — this is one of the main public-health messages about it, since it can practically only be detected with a blood test, not by how someone feels. If glucose levels approach the diabetic threshold, signs similar to diabetes symptoms can sometimes appear — increased thirst, frequent urination, fatigue.

What happens next if nothing changes

Without intervention, a substantial share of people with prediabetes go on to develop type 2 diabetes: estimates vary, with around 25% progressing within 3–5 years and up to 50% within 10 years; one frequently cited study puts the figure at 37% over 4 years. At the same time, the large-scale Diabetes Prevention Program study (US) found that intensive lifestyle changes reduced progression to diabetes by about 58% (and by up to 71% among people over 60) compared with a control group — this is presented as the result of a specific study, not a guarantee for every individual.

In the scientific literature, the progression of prediabetes to type 2 diabetes is described as something that can be slowed or even stopped through lifestyle changes. Only a doctor can give specific recommendations after an evaluation.