What Happens Between "Normal" and Prediabetic That Nobody Warns You About
The labs your doctor isn’t ordering and the nine habits to fix it
In old westerns, something strange happens to stagecoach wheels. As the coach picks up speed, the wheels appear to slow down. Then they stop entirely. Then, if the scene runs long enough, they start spinning backward. The coach is clearly moving forward, but the wheels look like they’ve changed their minds.
The wheels haven’t changed direction. The camera has a problem. Film works by taking still photographs in rapid sequence. If the camera’s frame rate is too slow for the speed of the wheel, it catches each spoke in a position that lookslike the wheel is barely turning. The real motion is fast, but the sampling rate is slow, so the image that reaches the audience is wrong. Engineers have a name for this. They call it aliasing. The signal looks smooth and calm, but only because the measurement tool isn’t fast enough to see what’s actually happening.
Your fasting glucose works the same way.
Every few months, you sit in a chair, extend your arm, and a lab tech draws blood first thing in the morning. The result comes back in the normal range. You feel reassured. Then your A1c arrives, and it’s a little higher than last time. Or a lot higher. Your doctor says to keep an eye on it. You’re confused because the fasting number looked fine.
These two tests aren’t contradicting each other. They’re measuring different things. Fasting glucose is a single frame of a fast-spinning wheel. A1c is more like a film that recorded the whole day, every day, for the past several months. The film is blurry and compressed, but it captured what the snapshot missed.
The question is what’s happening in those invisible hours.
Quick announcement: If your energy crashes every afternoon, your weight won’t move no matter what you do, and your labs keep creeping in the wrong direction, there is a reason, and it probably has nothing to do with discipline.
The Insulin Resistance Reversal Roadmap is the system I built to fix that. You wear a CGM so you can finally see what your body is actually doing. You build one small habit at a time so nothing falls apart. You get live coaching with me every Tuesday, Chef Martin’s recipes designed for your blood sugar, and a community of people who get it. By the end, you have a daily operating system that runs without willpower, and retest labs that make your doctor ask what you’ve been doing differently.
Join The Habit Healers Community. I’ll see you inside.
Now back to the article!
The Engineer Who Proved Your Blood Draw Isn’t Enough
In the 1940s, a mathematician named Claude Shannon published a proof that changed how engineers think about recording signals. The idea was simple but the implications were enormous. If you want to reconstruct a signal accurately, you need to sample it at least twice as fast as the signal changes. Any slower, and you get aliasing. The reconstructed version of the signal will look different from the real one, and you’ll have no way of knowing.
This idea became the foundation of digital audio, medical imaging, and virtually every system that converts a continuous process into discrete measurements. It also turns out to be directly relevant to glucose monitoring.
A biomedical engineer applied Shannon’s framework specifically to glucose. Using continuous glucose monitor data from people with type 1 diabetes, he analyzed the frequency content of the glucose signal and calculated the minimum sampling rate needed to capture what glucose is actually doing throughout the day. The answer was every 15 minutes. Sampling less often than that, and important dynamics start disappearing from the record.
Think about what that means for a fasting blood draw. You get one measurement every 90 days or so. The math says you need one every 15 minutes. That’s a sampling rate thousands of times slower than what’s required to see the full picture. The fasting number itself is accurate. But a single morning reading was never designed to represent 24 hours of glucose behavior. It captures the calmest moment of the day and treats it as the whole story.
A1c doesn’t have this blind spot in the same way. Hemoglobin A1c reflects the cumulative glucose exposure over the lifespan of your red blood cells, roughly four months, though the measurement is weighted toward the most recent weeks. It has its own limitations (more on that later), but it’s recording the entire performance. That’s why it can see things the fasting number misses.
Where the Hidden Glucose Lives
So if fasting glucose is capturing the quiet morning and A1c is capturing everything, the gap between them points somewhere specific. And the data are remarkably consistent on where that somewhere is. For people whose A1c is still in the lower range, the overwhelming majority of their total glucose elevation comes not from fasting levels but from what happens after meals.
The most important study on this question, conducted in people with type 2 diabetes, quantified the split. At lower A1c levels, postprandial glucose, the levels your body reaches in the one-to-three-hour window after eating, contributes roughly 70% of the total problem. Fasting glucose accounts for only about 30%. As A1c climbs higher, the ratio reverses. But for the person sitting in the early-warning zone, where fasting looks normal and A1c is creeping upward, the action is happening in that after-meal window.
Follow-up work from the same group found something even more telling. Postprandial glucose control doesn’t deteriorate alongside fasting glucose. It deteriorates first, in a stepwise sequence, with the after-meal window falling apart significantly before nocturnal fasting levels budge at all. By the time fasting glucose begins to move, the postprandial problem has already been building behind the scenes.
The most vivid demonstration of this came when researchers placed continuous glucose monitors on adults whose standard lab work looked completely normal. Even participants classified as normoglycemic by traditional measures spent time in prediabetic and diabetic glucose ranges, reaching prediabetic levels about 15% of the time and diabetic levels about 2% of the time. Participants spiked significantly after a standardized breakfast that no fasting blood draw would have detected.
The largest study of this kind, from a community-based cohort of more than a thousand adults without diabetes, put a finer point on the numbers. When measured against the tighter 70 to 140 mg/dL glucose window, normoglycemic participants spent only 87% of their day in that range. For the remaining 13% of the day, roughly three hours, their glucose was above 140. Among those already classified as prediabetic, time in that same range dropped to 77%, meaning nearly a quarter of their day was spent above 140 mg/dL. Three or more hours a day of elevated glucose, invisible on every fasting draw.
How do you fix it?
Your fasting glucose said you were fine. Your A1c disagreed. The question now is which number you want to change, and how. The paid section includes the labs worth asking for, the ranges your doctor’s report won’t flag, the nine habits that target the hours your blood draw never sees, and a printable worksheet to track it all. Upgrade now to access the full protocol.
