What Are Insulin Resistance, Prediabetes, and Type 2 Diabetes?

Updated July 2026

Disordered glucose metabolism is one of the most common health conditions affecting Americans today, and it shows up in three forms: insulin resistance, prediabetes, and type 2 diabetes. Chances are high that you've been personally affected or know someone who has.

This is the first article in a series on these conditions. The goal is to help you understand the disorders, determine your personal risk, understand the testing involved, and build a plan to avoid or reverse them — without simply resorting to more and more medication.

Are insulin resistance, prediabetes, and type 2 diabetes the same disease?

In a sense, yes. Insulin resistance (IR), prediabetes (PreDM), and type 2 diabetes (T2DM) are really the same disease at different levels of severity. They all represent a disturbance in blood sugar control, comprising a continuum of metabolic dysfunction. All people with T2DM were PreDM at some point. And all people with PreDM started out with IR. While therapeutic action typically ramps up once T2DM is diagnosed, we should be aggressively preventing progression much earlier in the disease process.

How are prediabetes and type 2 diabetes diagnosed?

Both are defined by thresholds on two common blood tests. Type 2 diabetes is diagnosed once your fasting blood sugar measures 126 mg/dL or higher on two separate occasions and/or your hemoglobin A1C (HbA1C) reaches 6.5% or greater. Prediabetes is diagnosed once your fasting blood sugar measures between 100 and 125 mg/dL on two separate occasions and/or your HbA1C falls between 5.7% and 6.4%.

Why do you need two blood glucose tests to diagnose diabetes?

Because a single measurement is only a snapshot. The blood sugar number on the lab report represents the concentration of glucose in your bloodstream at the moment the blood was drawn. But glucose levels vary minute to minute throughout the day and can change dramatically in response to meals. So one abnormal reading could be an outlier, and a single normal reading might not give the entire picture.

Why is hemoglobin A1C a better marker than blood sugar?

Because it reflects your average blood sugar over months, not a single moment. HbA1C provides a sense of overall blood sugar control over an extended period, typically the past 2–3 months. It's as if we assessed your blood glucose level every second of every day over the past 60–90 days and gave you an average.

Hemoglobin A1C is the measure of the proportion of hemoglobin (yes, the same stuff that carries oxygen in our red blood cells) that has a glucose molecule attached to it. This process of glucose attachment is called "glycosylation" and is irreversible. It's normal to find some of our hemoglobin in the glycosylated state. But as overall blood sugar control deteriorates and more glucose can be found circulating in our blood streams, more and more blood sugar ends up attached to our hemoglobin.

Because glycosylation is irreversible and because red blood cells (and the hemoglobin they contain) are recycled every 2-3 months, HbA1C is a backwards looking measurement that changes slowly. This is why we typically retest HbA1C once every 3 to 4 months at most.

How is insulin resistance detected when blood sugar looks normal?

It takes more than the standard tests, because in insulin resistance the usual numbers still look fine. In patients who are insulin resistant, fasting blood sugar and HbA1C fall into normal ranges, but that doesn't mean all is well — other clues exist that problems are brewing. Blood glucose and HbA1C levels are typically upper limits normal, triglyceride levels may be elevated, excess weight, especially in the abdominal region may be present. Elevated blood pressure and higher levels of inflammatory markers are also commonly seen in individuals with IR.

The definitive test for IR involves measuring not only blood sugar and HbA1C, but insulin levels and a compound called c-peptide. C-peptide is released in proportion to the amount of insulin your body is making. People with insulin resistance need to make more insulin to keep their blood sugars in the normal range. So blood sugars and HbA1Cs will be normal, but c-peptide levels will be elevated in people with IR.

The insulin measurement can be used in conjunction with your fasting glucose value to mathematically generate another result called a HOMA-IR (Homeostatic Model Assessment-Insulin Resistance) score. HOMA-IR scores greater than 1.0 typically indicate that IR is present, with levels over 2.0 indicating severe insulin resistance.

Checking c-peptide levels or calculating HOMA-IR is not something that is routinely done at annual physicals. This is why paying attention to the other clues is so important for both you and your physician. Because the earlier you catch the metabolic dysfunction, the easier it will be to correct.

How common are insulin resistance, prediabetes, and type 2 diabetes?

They now affect the majority of American adults. The CDC estimates that 38 million Americans have full-blown diabetes and 98 million have prediabetes. Another 48 million or so are estimated to have insulin resistance — nearly 75% of adults in our country.

What's really scary is that no matter where you fall on the spectrum of these disorders, your risk of developing downstream health issues is significantly increased. Those health issues include heart disease, peripheral vascular disease, stroke, erectile dysfunction, various forms of cancer, and even dementia.

And risk goes up logarithmically as you advance through the stages. So, IR is not benign. Prediabetes is most definitely NOT a pre-disease. And type 2 diabetes is an all-out metabolic emergency.

Can insulin resistance, prediabetes, and type 2 diabetes be reversed?

Often, yes. Regardless of where you fall on the spectrum, disordered glucose metabolism is often REVERSIBLE. Even type 2 diabetics can reverse their disease if it's caught early enough and intervened on aggressively enough. IR and PreDM are completely un-doable. The key is to start an all-out effort now, regardless of how far along you've traveled. The sooner the better.

Next up: How do these conditions develop?

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