Many people assume that if their blood sugar levels are normal, they must be metabolically healthy. After all, blood glucose is one of the main measurements used to screen for conditions like prediabetes and type 2 diabetes, and elevated levels are a well-established risk factor for cardiovascular disease.
But blood glucose doesn’t always tell the full story.
In some cases, blood sugar stays within the normal range because the body is producing high amounts of insulin to keep it there. On the surface, everything appears normal, but the underlying metabolic picture may be quite different.
When the Body Compensates
As blood glucose begins rising, the pancreas releases insulin, which signals cells to take up glucose from the bloodstream. When cells become less responsive to insulin – a condition known as insulin resistance – the pancreas compensates by producing more insulin.
For a period of time, this works. Fasting blood glucose remains within the range of 70–99 mg/dL (3.9–5.5 mmol/L), HbA1c stays below 5.7%, and metabolic dysfunction may go unnoticed. But behind the scenes, insulin levels may be elevated because the pancreas is working harder to maintain that “normal” blood sugar.
This compensatory state can persist for years before glucose levels begin to rise.
A Closer Look: Insulin-Compensated Euglycemia
A 2026 paper by Cooper and colleagues explored this phenomenon in more detail and introduced the term insulin-compensated euglycemia (ICE).
In this study, lean, healthy women who had maintained a ketogenic lifestyle for several years were instructed to increase their carbohydrate intake to more than 200 grams per day for three weeks. The researchers then measured changes in their blood glucose, insulin, and ketone levels.
Despite the substantial increase in carbohydrate intake, many participants maintained blood glucose levels within the normal range. However, this was accompanied by a significant rise in insulin levels and a marked suppression of ketone production.
In other words, glucose remained normal, but only because insulin increased to manage the higher carbohydrate load. When the women returned to their usual very low-carbohydrate intake, insulin levels decreased and ketone production resumed, reflecting a shift back toward a lower-insulin state.
Importantly, this study was conducted in a specific population under controlled conditions: lean, healthy women who had been keto-adapted for years and then underwent a short-term increase in carbohydrate intake. Even so, the results illustrate how normal glucose levels can mask underlying metabolic changes.
Why This Matters
These findings highlight an important point: normal glucose and HbA1c levels don’t necessarily mean that insulin levels are low or that metabolic health is optimal.
Persistently elevated insulin levels (hyperinsulinemia) have been linked to a range of metabolic concerns, even when blood glucose remains within the normal range. Over time, the pancreas may no longer be able to sustain this increased insulin output. When that happens, blood glucose begins to rise, and conditions like prediabetes or type 2 diabetes may be diagnosed. But by that stage, metabolic dysfunction has often been present for years.
Moreover, while fasting glucose and HbA1c are valuable tools, they tend to detect changes later in the process. This means someone can appear metabolically healthy based on these values alone, while underlying insulin dynamics tell a different story.
Carbohydrate Reduction, Ketones, and Metabolic Insight
When carbohydrate intake is significantly reduced, insulin levels decline, allowing the body to use fat for fuel. The liver converts these fatty acids into ketones, including beta-hydroxybutyrate (BHB), which rise in the bloodstream within a period of a few days.
This is where measuring ketones can provide valuable insights. Because insulin suppresses ketone production, ketone levels can provide insight into how much insulin is circulating relative to the body’s needs:
- Low ketones alongside normal glucose can suggest that insulin is relatively elevated.
- Measurable ketones with normal glucose generally reflect lower insulin levels and greater metabolic flexibility.
In her papers, Dr. Cooper describes a personalized hyperinsulinemia threshold (PIT), the point at which insulin is too high for an individual’s metabolic capacity. In the context of someone following a ketogenic or low-carbohydrate lifestyle, consistently low ketone levels – BHB below 0.5 mmol/L after not eating for at least three hours – suggest that insulin may be elevated relative to that individual’s needs, even if it falls within standard fasting insulin ranges.
Tracking ketones, with or without glucose, can therefore provide a simple way to observe how one’s metabolism is responding over time and whether dietary or other adjustments need to be made in order to ensure progression in the right direction.
A Broader View of Metabolic Health
Maintaining normal blood sugar is important, but how it is maintained is equally important.
As research illustrates, glucose can remain within the normal range even when insulin levels are elevated. This state – insulin-compensated euglycemia (ICE) – may represent an earlier stage of metabolic dysfunction.
Assessing one’s personalized hyperinsulinemia threshold by using blood ketone measurements can help determine whether insulin levels are elevated relative to the person’s needs. This may provide useful insight into whether diet and lifestyle factors require adjusting in order to optimize their metabolic health.
