Your last blood test missed this.

Your next checkup will probably include one blood test for your sugar control. It is called HbA1c. It averages your blood sugar over three months. It is a good test. It is also a late one.

There is another test, older and cheaper, that catches the same problem more than a decade earlier. Almost no one runs it. Most doctors have never offered it to you.

Here is the simplest way to picture what HbA1c misses.

Imagine your pancreas is the smoke alarm in your kitchen. Every time you eat, your pancreas releases insulin, the hormone that moves sugar out of your bloodstream and into your cells. When you are young and metabolically healthy, that takes a small amount of insulin and the smoke alarm stays quiet.

When something starts to go wrong, your cells stop listening to insulin as well as they used to. Your pancreas compensates by producing more. Then more. The smoke alarm starts running constantly to keep the kitchen from setting on fire. From the outside, everything looks fine. Your blood sugar still tests normal. The pancreas is just working twice as hard to keep it there.

This phase can last a decade or more. The pancreas can compensate for a long time. The point at which HbA1c moves is the point at which the pancreas finally cannot keep up and blood sugar starts to drift high. That is the fire. By the time HbA1c catches it, the smoke alarm has been screaming for years.

The test that measures the smoke is called fasting insulin. It is drawn the same way as your fasting glucose, the morning blood test you have probably had many times. One tube of blood, before breakfast. It tells you how hard your pancreas is working when nothing in your bloodstream is asking it to.

A clinical pathologist in Chicago named Joseph Kraft built the case between 1972 and 1998 at St. Joseph Hospital. Patients drank a sugar solution. He drew their blood every thirty minutes for three hours, measuring both glucose and insulin. He ran 14,384 of these tests. He published the framework in Laboratory Medicine in 1975 and the dataset grew for another twenty-three years.

The finding that has propagated through metabolic medicine since. Three quarters of the adults whose standard glucose test looked normal had abnormal insulin response patterns. Their pancreas was already compensating. The glucose just had not yet caught up. Kraft called this state diabetes in situ, which translates roughly as "diabetes already in place but not yet visible on the standard test." The five insulin response patterns he identified track the trajectory from healthy through compensated to overt type 2 diabetes.

The work has held up across other cohorts. Tirosh et al, in the New England Journal of Medicine in 2005, tracked 13,163 young men in the Israeli army for twelve years. Fasting glucose values still inside the "normal" range predicted type 2 diabetes a decade later. The signal Kraft saw in insulin showed up in glucose, just much later. A research team led by Catherine Crofts at the Auckland University of Technology has spent the last decade consolidating the hyperinsulinemia trajectory data with newer cohorts. Their 2017 follow-up puts the average lead time between abnormal insulin and abnormal HbA1c at more than a decade. The exact figure varies by individual. The direction does not.

The pushback from standard medicine is that fasting insulin lacks a tight "normal" range the way fasting glucose does. That is partly true. Australian pathology labs report a reference up to 20 mIU/L, which is loose enough to call almost anyone normal. The clinical literature on insulin sensitivity converges on a much tighter band, and that is the one worth using.

Ask for two numbers at your next blood draw. Fasting insulin. Fasting glucose. Drawn together, before breakfast, no other prep required. Track them once a year. The trend will tell you whether your deposits are working long before HbA1c will.

If your GP declines, the route is direct-to-consumer. In Australia, i-Screen sells the Insulin Resistance and Diabetes Risk Test direct. You download a pathology form, take it to a Sonic or affiliated collection centre, the result lands in your dashboard. Roughly $80 AUD. For readers in the United States, Function Health bundles fasting insulin into its 100-plus-marker annual panel at around $499 USD; Ulta Lab Tests sells the single fasting insulin assay for around $30 USD plus a phlebotomy fee.

The interpretation matters more than the test. If your fasting insulin lands above 6, the action layer is the same one the brand has named for ten months. Less ultra-processed food. More protein at breakfast. Two resistance training sessions a week. Sleep regularity. Daily walking. The metabolic system responds to the same handful of inputs whether you are catching the problem early or late. Catching it early just means a much smaller correction.

For the deepest read on why insulin became the master signal most clinicians do not measure, Why We Get Sick by Benjamin Bikman is the cleanest current introduction. The first three chapters are the highest-leverage hour on the topic this year.

The wellness industry has built a multi-billion-dollar category on the idea that wearing a continuous glucose monitor will reveal what your metabolism is doing. The largest study of 7,104 non-diabetic adults says the device, in this population, is mostly measuring itself. We walk through what the data showed, where the device is genuinely medicine, and where the marketing has outrun the evidence. Wednesday.

Longevity Daily · The Building Decades

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P.S. If you have not yet, the Healthspan Score is the five-minute assessment that surfaces which of your metabolic markers is most likely the next lever. Free, no blood draw.

P.P.S. If your blood results come back with both numbers, a quick at-home calculation gives you a single insulin-sensitivity score: fasting insulin times fasting glucose, divided by 405. Below 1.5 is healthy. The formula is called HOMA-IR; any web calculator will do the math for you.

Sources: Kraft, Laboratory Medicine 1975 · Tirosh et al, NEJM 2005 · Crofts et al, Diabesity 2015 · Crofts et al, Open Heart 2017

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