Prediabetes

What it is

Prediabetes is blood sugar above normal but below diabetes, often defined by an A1C of 5.7% to 6.4%. It is an intermediate state of abnormal glucose regulation, sometimes called impaired fasting glucose or impaired glucose tolerance, and it raises the risk of developing type 2 diabetes, heart disease, and stroke. Many people have no symptoms, so it is often found on routine blood tests rather than because a person feels unwell.

Prediabetes is not the same as diabetes, but it is not harmless. Some people return to normal glucose levels with weight loss, regular physical activity, and dietary changes, while others progress to type 2 diabetes over time. Risk is higher in people with excess body weight, a family history of diabetes, prior gestational diabetes, polycystic ovary syndrome, fatty liver disease, or low physical activity. In India, this matters because South Asians often develop insulin resistance and type 2 diabetes at lower body mass index values than many White populations, so screening may be appropriate even when obesity is not obvious.

A quick comparison:

Test	Prediabetes range
A1C	5.7% to 6.4%
Fasting plasma glucose	100 to 125 mg/dL
2-hour glucose after 75 g oral glucose tolerance test	140 to 199 mg/dL

How it works

Prediabetes usually develops because the body becomes less responsive to insulin, a hormone made by the pancreas that helps glucose move from the blood into cells. This is called insulin resistance. At first, the pancreas can often compensate by making more insulin. Over time, that compensation may become inadequate, and blood glucose starts to rise.

Several organs are involved. Muscle takes up less glucose, the liver releases more glucose than it should, and fat tissue can contribute to inflammation and metabolic dysfunction. Genetics, sleep problems, stress, some medicines, and excess visceral fat can all play a role. In many people, prediabetes is part of a broader metabolic pattern that may include high triglycerides, low HDL cholesterol, elevated blood pressure, and central obesity.

Prediabetes can appear in different patterns:

1. Impaired fasting glucose (IFG): fasting sugar is high, often reflecting increased liver glucose output.
2. Impaired glucose tolerance (IGT): the 2-hour glucose after a glucose drink is high, often reflecting reduced muscle glucose uptake.
3. Elevated A1C: average blood glucose over about 3 months is above normal but below the diabetes threshold.

These categories overlap, but not always. A person may meet one criterion and not another.

Evidence and uses

Prediabetes is mainly a risk state, not a disease label used to justify automatic medication for everyone. The main reason to identify it is to prevent or delay type 2 diabetes and reduce cardiovascular risk.

The strongest evidence supports lifestyle change. In major prevention trials, modest weight loss and regular physical activity reduced progression from prediabetes to diabetes. Common targets used in prevention programs include at least 150 minutes per week of moderate-intensity physical activity and about 5% to 7% weight loss for people who are overweight. Benefits are often seen even before large weight changes occur.

Dietary approaches do not need to be identical for everyone. Patterns that emphasize minimally processed foods, vegetables, pulses, whole grains, nuts, and adequate protein tend to help. Reducing sugar-sweetened beverages and highly refined carbohydrates is especially relevant in populations with high insulin resistance. In India, practical changes may include smaller portions of polished rice, sweets, and refined flour foods, while increasing dal, vegetables, curd, and higher-fiber grains where culturally acceptable.

Medication is sometimes used, but it is not first-line for most people. Metformin has the best evidence and is often considered for people at particularly high risk, such as those with higher fasting glucose, higher A1C, younger age with obesity, or a history of gestational diabetes. It is less effective than intensive lifestyle intervention in many prevention studies, though still useful in selected patients.

Prediabetes is also associated with other health problems even before diabetes develops. These can include fatty liver disease, early nerve symptoms, kidney risk, and increased cardiovascular risk. That is why clinicians often look beyond glucose alone and also address blood pressure, lipids, sleep apnea, smoking, and waist circumference.

Diagnosis / how it's measured

Prediabetes is diagnosed with laboratory testing, not symptoms alone. The three standard tests are fasting plasma glucose, A1C, and the 75 g oral glucose tolerance test.

• A1C: reflects average glucose over the previous 2 to 3 months. Prediabetes is 5.7% to 6.4%.
• Fasting plasma glucose: measured after an overnight fast. Prediabetes is 100 to 125 mg/dL.
• Oral glucose tolerance test: blood glucose is measured 2 hours after drinking 75 g of glucose. Prediabetes is 140 to 199 mg/dL.

Each test has strengths and limits. A1C is convenient because fasting is not required, but it can be misleading in some conditions that affect red blood cells, such as anemia, hemoglobin variants, recent blood loss, or chronic kidney disease. The oral glucose tolerance test is more sensitive for some people, but it is less convenient and more variable.

Because results can differ by test, clinicians may repeat testing or use a second method if the picture is unclear. Screening is especially important in adults with overweight or obesity and additional risk factors, and in people with prior gestational diabetes. In South Asian populations, including many Indians, clinicians may screen earlier because diabetes risk can appear at lower body weights.

When to see a clinician

See a clinician if you have risk factors for diabetes, such as excess abdominal weight, a strong family history, prior gestational diabetes, PCOS, high blood pressure, abnormal cholesterol, fatty liver disease, or sleep apnea. You should also ask about testing if you have dark velvety skin patches called acanthosis nigricans, or if routine blood work has shown borderline high glucose.

If you already have prediabetes, follow-up matters. Your clinician may recommend repeat glucose testing every 1 to 3 years depending on your results and risk profile. Seek prompt care sooner if you develop symptoms more typical of diabetes, such as increased thirst, frequent urination, unexplained weight loss, blurred vision, or recurrent infections.

Limitations and open questions

Prediabetes is a useful clinical concept, but it has limits. Not everyone with prediabetes progresses to diabetes, and some people return to normal glucose levels. Risk varies by which test is abnormal, how high the value is, age, body composition, ethnicity, and other metabolic factors.

There is also debate about how broadly the label should be applied, because diagnostic cutoffs identify a large number of people with very different levels of risk. Evidence is strongest for lifestyle intervention, but less clear on which exact diet works best for each person and when medication should start outside high-risk groups.

Research continues on better ways to personalize risk, including combining glucose tests with measures of liver fat, insulin resistance, genetics, and continuous glucose monitoring. For now, the most reliable message is practical: prediabetes deserves attention, but it is often reversible or improvable with sustained changes and regular follow-up.