Your fasting glucose is normal. Your A1C is normal. And yet you have been told, or you suspect, that something about your metabolism is not working the way it used to. How can both be true?
The answer lies in how the body defends its blood sugar, and in which number moves first.
What insulin does
After you eat, glucose from food enters the bloodstream. Insulin, a hormone made by the pancreas, moves that glucose into your cells, where it is used for energy. It also signals the liver to store extra glucose for later.
When the system works well, a modest amount of insulin is enough to do this.
What changes with insulin resistance
Insulin resistance is a condition in which the body does not respond to insulin the way it should. The cells still need glucose, but they respond less readily to insulin's signal.
The pancreas does not simply accept this. According to the Centers for Disease Control and Prevention, it pumps out high levels of insulin to get more blood sugar into the cells. In effect, it raises its voice to be heard.
For a time, that extra effort can keep blood glucose from rising. This is the stage the title describes: glucose looks normal because insulin is working harder to keep it there.
The CDC describes what can happen next. Eventually the pancreas cannot keep up, and blood sugar keeps increasing. When glucose rises above normal but not yet to the level of diabetes, it is called prediabetes.
Why glucose is the later signal
Put those stages in order and the pattern becomes clear. Rising insulin is the effort. Rising glucose is what happens when the effort is no longer enough. That is why a normal glucose result does not, on its own, rule out insulin resistance, and why people with insulin resistance and prediabetes usually have no symptoms.
It also explains how common this is without anyone knowing. In 2021, about 97.6 million adults in the United States had prediabetes, and the CDC has reported that more than 8 in 10 adults with prediabetes do not know they have it.
The numbers that define prediabetes
Prediabetes is diagnosed with established tests and cutoffs, published by the National Institute of Diabetes and Digestive and Kidney Diseases:
A1C: 5.7% to 6.4%
Fasting plasma glucose: 100 to 125 mg/dL
Oral glucose tolerance test, 2 hours: 140 to 199 mg/dL
These are the thresholds clinicians use. A result below them is reassuring about glucose. It does not describe how hard the pancreas is working to keep it there.
What about measuring insulin?
It seems logical to measure insulin directly, and a fasting insulin test can do that. It is worth understanding its limits honestly.
Insulin levels vary depending on blood glucose, so a single insulin result is usually not enough on its own. It is typically read alongside other tests, such as fasting glucose and A1C. Reference ranges vary between laboratories, and the test usually requires fasting for 8 to 12 hours. The federal government also notes that the formal test for insulin resistance is used mainly in research, and that clinicians may not test for it at all.
So fasting insulin is best understood as context rather than a diagnosis. Read with glucose, A1C, triglycerides, and your history, it can help show whether the body is compensating. It is not a number to interpret alone, and no single optimal value has been established for it.
Why this stage matters
The stage before glucose rises is the stage with the most room to act. In the Diabetes Prevention Program, a large federal trial in people at high risk for type 2 diabetes, participants who aimed to lose 7 percent of their body weight and exercise 150 minutes a week lowered their chances of developing type 2 diabetes by 58 percent over about three years.
Physical activity makes the body more sensitive to insulin. For people with overweight or obesity, weight loss can increase insulin sensitivity too. Balanced eating lowers blood sugar, which reduces how much insulin the pancreas has to release. Sleep and stress management support all of it.
A normal glucose result is good news. It is not always the whole story, and the earlier the rest of the story is understood, the more can be done with it.
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This article is general education. It is not medical advice and does not replace care from your own clinician.
Sources
Centers for Disease Control and Prevention. Insulin Resistance and Type 2 Diabetes. May 15, 2024.
National Institute of Diabetes and Digestive and Kidney Diseases. Insulin Resistance & Prediabetes. Last reviewed March 2025.
Centers for Disease Control and Prevention. Prediabetes: You Could Be That 1 in 3. Archived; last updated June 29, 2022.
MedlinePlus, National Library of Medicine. Insulin in Blood. Last updated September 30, 2026.
National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes Prevention Program (DPP).
