Insulin Resistance: How It Is Diagnosed and Treated

Insulin resistance is often talked about as if it is the same thing as prediabetes, but it usually develops years earlier, while glucose and A1C still look completely normal. Understanding the difference matters because it changes when intervention should actually start.

Why glucose can be normal while insulin resistance is already present

When cells become less responsive to insulin, the pancreas compensates by producing more of it, and for years this compensation is often enough to keep blood glucose in the normal range. Fasting glucose and A1C, the two most common screening tests, only become abnormal once the pancreas can no longer fully compensate. By that point, insulin resistance has typically been present for a meaningful stretch of time already.

This is why a "normal" glucose result does not rule out insulin resistance, particularly in people with other risk factors: excess abdominal fat, a sedentary pattern, a family history of type 2 diabetes, or polycystic ovary syndrome.

How insulin resistance is actually identified

There is no single test used routinely in general practice to diagnose insulin resistance directly. The most practical clinical approach is a fasting insulin level drawn alongside fasting glucose, which can be used to calculate a HOMA-IR score, a widely used research and clinical estimate of insulin sensitivity. An elevated fasting insulin with a still-normal glucose is a meaningful early signal, even without a formal HOMA-IR calculation.

Waist circumference and the distribution of body fat also matter clinically. Visceral fat, the fat stored around abdominal organs rather than under the skin, is more metabolically active and more strongly associated with insulin resistance than overall body weight alone. Two people at the same weight can have meaningfully different insulin resistance risk based on where that weight is carried.

What actually improves insulin sensitivity

Weight loss, specifically loss of visceral fat, is the most effective non-medication intervention, and the effect shows up with a relatively modest amount of weight loss, often 5 to 10 percent of body weight, well before reaching a lower target weight.

Regular physical activity improves insulin sensitivity through a separate mechanism from weight loss: exercising muscle takes up glucose without requiring as much insulin, meaning activity helps even before any change on the scale. Resistance training in particular has strong evidence for improving insulin sensitivity by increasing muscle mass, which increases the body's overall capacity to use glucose.

Medication options when lifestyle change is not enough

Metformin remains the most established medication for insulin resistance and works by reducing glucose production in the liver and improving peripheral insulin sensitivity. GLP-1 medications also improve insulin sensitivity, largely as a downstream effect of the weight loss they produce, and are increasingly used when insulin resistance is present alongside significant excess weight.

Catching it before it becomes prediabetes

If you have risk factors for insulin resistance, excess abdominal fat, a sedentary lifestyle, PCOS, or a family history of type 2 diabetes, a fasting insulin level alongside your regular glucose testing can catch this process years before it would otherwise show up. Most major insurance plans, including Medicare, cover this testing as part of a metabolic risk evaluation.