What Is Prediabetes: Risk Factors, Symptoms, and Reversing the Condition

This article is for informational purposes only. Consult a qualified healthcare professional for medical advice, diagnosis, or treatment.

What Is Prediabetes?

Prediabetes is a metabolic condition in which blood glucose levels are higher than normal but not yet high enough to meet the diagnostic criteria for type 2 diabetes. It represents an intermediate state of insulin resistance and impaired insulin secretion, placing individuals at substantially elevated risk of progressing to full type 2 diabetes if no intervention is made. The Centers for Disease Control and Prevention (CDC) estimates that approximately 96 million American adults — more than 1 in 3 — have prediabetes, and of those, more than 80% are unaware of their condition because it rarely causes noticeable symptoms. Globally, the International Diabetes Federation estimated 541 million adults had impaired glucose tolerance in 2021, with projections rising to 730 million by 2045.

Diagnostic Criteria

Three laboratory tests can identify prediabetes, each reflecting different aspects of glucose metabolism:

The fasting plasma glucose category (100–125 mg/dL) is called impaired fasting glucose (IFG); the 2-hour OGTT category is called impaired glucose tolerance (IGT). A person may have either or both, and having both IFG and IGT carries a higher conversion risk to diabetes than either alone.

Underlying Biology: Insulin Resistance and Beta-Cell Dysfunction

Prediabetes develops through two interrelated processes. First, insulin resistance develops in peripheral tissues — primarily skeletal muscle, liver, and adipose tissue — which no longer respond normally to insulin signals. As a result, muscle cells take up less glucose, and the liver continues producing glucose despite adequate insulin levels. Second, the pancreatic beta cells initially compensate by secreting more insulin; over time, they become exhausted and their secretory capacity declines. This beta-cell dysfunction, combined with worsening insulin resistance, drives the progressive rise in blood glucose.

Central to this process is ectopic fat accumulation — excess fat deposited in visceral adipose tissue, the liver (hepatic steatosis), and intramyocellular compartments. Visceral fat releases inflammatory cytokines (TNF-α, IL-6, resistin) and free fatty acids that interfere with insulin signaling cascades, particularly the PI3K/Akt pathway, reducing glucose transporter (GLUT4) translocation to the cell surface.

Risk Factors

• Overweight and obesity: Body mass index ≥25 kg/m² (or ≥23 kg/m² for Asian populations) is a primary risk factor. Visceral obesity is more metabolically harmful than overall body fat.
• Physical inactivity: Sedentary behavior reduces skeletal muscle glucose uptake and reduces mitochondrial capacity to oxidize fatty acids, exacerbating insulin resistance.
• Family history: Having a first-degree relative with type 2 diabetes increases risk approximately 2.4-fold, reflecting both genetic predisposition and shared lifestyle environments.
• Age: Risk increases with age, particularly after 45, as beta-cell function naturally declines and physical activity tends to decrease.
• Gestational diabetes: Women who develop gestational diabetes have a 50% lifetime risk of developing type 2 diabetes.
• Polycystic ovary syndrome (PCOS): Insulin resistance is a central feature of PCOS, making affected women 4–8 times more likely to develop type 2 diabetes.
• Race and ethnicity: African American, Hispanic/Latino, American Indian, Alaska Native, Pacific Islander, and certain Asian American populations face higher prediabetes prevalence.
• Sleep disorders: Obstructive sleep apnea and short sleep duration impair insulin sensitivity and glucose metabolism.

Symptoms and Complications

Prediabetes itself is almost always asymptomatic, which is why screening is critical. Occasionally, people may experience mild fatigue, increased thirst, or slightly blurred vision, but these are nonspecific. The concern lies in what prediabetes can progress to:

• Without intervention, approximately 15–30% of individuals with prediabetes progress to type 2 diabetes within 5 years.
• Prediabetes is associated with early microvascular damage, including subclinical retinopathy and peripheral neuropathy, even before diabetes is diagnosed.
• Cardiovascular risk begins elevating in the prediabetic range, with elevated risks of coronary artery disease, heart failure, and stroke.
• Non-alcoholic fatty liver disease (NAFLD) frequently coexists with prediabetes and insulin resistance.

Reversal and Prevention Strategies

Dietary Approaches

No single diet is superior for prediabetes reversal, but consistent evidence supports reducing refined carbohydrates, added sugars, and ultra-processed foods while increasing dietary fiber, lean proteins, and unsaturated fats. The Mediterranean diet — rich in vegetables, legumes, whole grains, olive oil, fish, and moderate red wine — consistently reduces HbA1c and cardiovascular risk markers. Low-carbohydrate diets can produce rapid improvements in fasting glucose and insulin resistance, though long-term adherence varies. The PREDIMED trial (2013, with 7,447 participants) demonstrated that a Mediterranean diet supplemented with olive oil reduced incident type 2 diabetes by 52% versus a low-fat diet.

Physical Activity

Both aerobic exercise and resistance training improve insulin sensitivity independently of weight loss. Aerobic exercise increases GLUT4 transporter expression in muscle; resistance training increases muscle mass, the body's largest glucose sink. A combination of both types is recommended, distributed across multiple days to maximize duration of improved insulin sensitivity (which is time-limited after each exercise bout).

Structured programs such as the CDC's National Diabetes Prevention Program (National DPP) translate the DPP trial lifestyle intervention into community settings, delivering similar results at far lower cost. Early recognition and action on prediabetes remains one of the most impactful preventive health strategies available.