Glucose sensors

Do you need a CGM? Why glucose isn't the only number to track

By GyroscopeUpdated November 15, 202610 sources

Glucose is one signal, and for people without diabetes it’s not the strongest one. No trial has shown that wearing a sensor improves health if you don’t have diabetes. Meanwhile your weight, your fitness, your blood pressure and your sleep each predict your future health more than the shape of the hill after lunch. A few weeks with a sensor can teach you about your meals, and then it should come off rather than become the scoreboard.

Why sensors feel so important

A sensor gives you a number every few minutes, a graph that moves while you watch and a score each evening. That makes glucose feel like the main thing going on in your body. Feeds full of spike charts add to it.

But a number you see constantly isn’t the same as the number that predicts the most. Some of the measures that predict health best change slowly and get checked rarely.

The counterpoints

The evidence for wearing one is thin. A 2026 review of 12 studies in adults without diabetes found sensors may help some diet changes inside a program, but “large, durable benefits and stand-alone efficacy are not established.” The certainty was low for diet results and very low for everything else, including whether sensors cause anxiety.

The number is off. In 15 healthy adults, a popular sensor ran about 16 mg/dL above fingertip blood and overstated the time above 140 about 4-fold. Sensor numbers are good for comparing one meal with another and loose for anything else.

Hills are normal. Healthy people spent about 30 minutes a day above 140 on a sensor. Nobody has shown that flattening normal hills prevents disease in people without diabetes.

A flat line isn’t the same as a healthy meal. Glucose only tracks carbs. Fried foods can make a smaller hill than a boiled potato (french fries 63 on the GI scale, boiled potato 78) and peanut M&M’s tested at 33, lower than a bowl of rolled oats at 55, because fat slows the sugar. If you chase the flattest curve, you can end up eating worse.

The numbers that predict more

Fitness. In 122,007 adults who took a treadmill test at the Cleveland Clinic, the least fit had about 5 times the risk of death of the fittest over about 8 years, more than smoking or diabetes carried in the same study. vo2max.guide covers why fitness predicts so much.

Weight. In the biggest diabetes prevention trial, each kilogram lost went with 16% lower diabetes risk. A scale and a tape measure tell you more about your diabetes risk than a sensor does. bodyfat.guide has the guide to losing fat.

Blood pressure and blood fats. Insulin resistance travels with high blood pressure and unhealthy cholesterol and triglycerides, according to the NIDDK. bloodpressure.guide’s checker and cholesterol.guide’s guide cover those.

Sleep. A week of 5-hour nights cut insulin sensitivity by 11% in healthy men. hrv.guide covers how to recover better.

Your lab A1c. More than 2 in 5 American adults have prediabetes and 8 in 10 of them don’t know. One blood test tells you more than a month of sensor data. lifespan.guide ranks what adds the most years, and blood sugar is one line on a long list.

When a sensor is a good idea

Two weeks to learn which of your own meals make big hills, a check on whether walking after dinner works for you, or a nudge to change a habit you already know about. For that, it’s a useful tool. What a CGM shows about your meals has the experiment, and is every blood sugar spike bad for you? covers the hills themselves.