Continuous glucose monitors for non-diabetics: are they worth it?

For most people without diabetes, a continuous glucose monitor (CGM) is an interesting short-term experiment rather than a proven health tool. Healthy adults spend about 96% of the day between 70 and 140 mg/dL, and there is no solid evidence yet that tracking glucose improves outcomes for people with normal metabolism. A CGM is most worth considering if you have prediabetes, a strong family history or other risk factors, and it is best used alongside a physician, not instead of one.

Since March 2024 you no longer need a prescription to find out for yourself. That has put small sensors on a lot of executive arms. Here is what the data can and cannot tell you.

What changed in 2024?

On March 5, 2024, the FDA cleared the Dexcom Stelo Glucose Biosensor System, the first continuous glucose monitor available over the counter. The agency cleared it for "anyone 18 years and older who does not use insulin," including people who manage diabetes with oral medication and people without diabetes who want to understand how diet and exercise affect their blood sugar. Each sensor can be worn for up to 15 days. Other manufacturers have since brought over-the-counter systems to market as well.

Two lines in that announcement are worth reading closely.

First, the device is not for "individuals with problematic hypoglycemia (low blood sugar) as the system is not designed to alert the user to this potentially dangerous condition." Prescription CGMs used in diabetes care have alarms. Consumer versions may not.

Second: "Users should not make medical decisions based on the device's output without talking to their healthcare provider." That is the FDA telling you the device is a window, not a diagnosis.

What a CGM actually measures

A CGM does not sample blood. A thin filament under the skin reads glucose in the interstitial fluid, the fluid around your cells, and sends a reading to your phone every few minutes. Interstitial glucose tracks blood glucose closely but trails it, especially when levels are changing fast after a meal or during exercise. That lag is one reason a single reading can look alarming and then settle on its own.

The value is in the continuity. A finger-stick or a lab draw is one frame. A CGM is the whole film: overnight, through the 3 p.m. slump, across a travel day with airport food and no movement. For someone who has only ever seen a single fasting number once a year, the film is genuinely new information. Whether that information changes anything important is the harder question.

How common is a glucose problem among people who feel fine?

This is where the case for testing gets stronger. The CDC's National Diabetes Statistics Report estimates that 115.2 million U.S. adults have prediabetes. Among adults with diabetes, 27.6% are undiagnosed, about 11.0 million people.

Put those numbers against a typical founder profile: long days, a lot of sitting, irregular meals, short sleep, and an annual physical that slipped to every other year. Plenty of people in that group have blood sugar drifting upward without knowing it. The right first step for them is a standard blood test ordered by a physician, such as fasting glucose or HbA1c. A CGM can add texture afterward. It does not replace the screening.

What does normal glucose look like on a CGM?

This is the question almost nobody asks before putting on a sensor, and it is the one that prevents most of the anxiety later.

The best reference comes from a 2019 multicenter study led by Viral Shah and published in the Journal of Clinical Endocrinology & Metabolism. Researchers put CGMs on 153 healthy participants aged 7 to 80 without diabetes and recorded what their glucose actually did.

Mean glucose was 98 to 99 mg/dL for every age group except people over 60, whose average was 104 mg/dL. Median time between 70 and 140 mg/dL was 96%. Median time above 140 mg/dL was 2.1%, about 30 minutes a day. Median time below 70 mg/dL was 1.1%, about 15 minutes a day.

Read that chart as permission to relax. Healthy people spike above 140 sometimes. Healthy people dip below 70 sometimes. Half an hour a day above 140 after meals is inside the normal pattern for this group. If you put on a CGM, see 150 after a bowl of pasta and conclude your metabolism is broken, you have learned the wrong lesson.

The study also found a mean within-person coefficient of variation of 17%. Glucose moves. That is what it is supposed to do.

What the evidence says, and what it doesn't

Strong: CGMs improve glucose management in people with diabetes, which is what they were built for. The FDA clearance for over-the-counter use is real, and the devices measure what they claim to measure within the limits of the technology.

Moderate: We now have reasonable reference data for what glucose looks like in healthy people, from studies like Shah's. Prediabetes and undiagnosed diabetes are common, so there is a real population that could benefit from earlier awareness.

Early or weak: Whether wearing a CGM improves long-term health for people without diabetes. In 2024 Harvard Health's editor in chief, Dr. Anthony Komaroff, put it plainly: "There is no solid evidence of the value of these monitors in people who do not have diabetes." He expects they may prove useful for people with risk factors, such as prediabetes, excess weight or a family history, but notes that this "will need to be scientifically established."

Not supported: The idea that every glucose spike is damage, that flattening every curve is a longevity strategy, or that a two-week trace can tell you your ideal diet with precision. Those claims run well ahead of the data.

Harvard Health also flags a practical point: CGMs "can be expensive and are not always covered by insurance." Over-the-counter use is typically out of pocket.

Who might reasonably try one?

People with known risk factors. If your last physical flagged borderline glucose, or diabetes runs in your family, a CGM can make abstract risk concrete. Seeing what a late dinner or a sedentary travel day does to your readings can be more motivating than a single lab number. Do it with your physician in the loop.

Curious operators who will run a bounded experiment. Two weeks, a few specific questions, then stop. For example: What does a 15-minute walk after lunch do? How does my usual breakfast compare with a higher-protein one? What happens on nights I sleep five hours?

People who want to see the stress signal. This is where CGMs get interesting for founders. Stress hormones release glucose into the blood to fuel a response, and short sleep is linked to higher glucose and insulin (we cover the physiology in what chronic stress does to a founder's body). Many wearers notice their numbers run higher on the day of a tense board meeting or after a bad night, even with identical food. That can be a useful, visible nudge toward protecting sleep.

Who should probably skip it?

Anyone prone to health anxiety or compulsive tracking. A live number on your phone, updated every few minutes, is a new thing to check at 2 a.m. If you already refresh dashboards compulsively, this is one more. Our piece on meditation for anxiety for founders covers the checking loop in more detail.

Anyone with a history of disordered eating. Close food and glucose tracking can reinforce restriction. Talk to a clinician first.

Anyone who will use it instead of a physical. A CGM is not a diagnostic test for diabetes. A fasting glucose or HbA1c ordered by a physician is.

Anyone taking glucose-lowering medication, or with symptoms of low blood sugar, should not rely on an over-the-counter device for safety. The FDA is explicit that Stelo is not designed to alert users to dangerous lows.

How to run a two-week CGM experiment that's actually useful

If you decide to try one, a little structure turns an expensive gadget into useful information.

Before you start, get the basics. Book a physical or at least a standard blood panel. If you already know your fasting glucose and HbA1c, the CGM data has context.

Write down three questions. Specific ones. "How does my body handle my usual work lunch?" "Does a walk after dinner change my overnight readings?" "What does a short night do to the next day?" Vague curiosity produces vague answers.

Change one thing at a time. If you change breakfast, bedtime and training in the same week, you will not know what moved the line.

Log context, not just food. Note sleep, alcohol, training, and the stressful meetings. For many founders the most surprising pattern is how much the calendar shows up in the curve.

Look at the pattern, not the peak. Compare against the healthy reference: most of the day between 70 and 140, brief excursions above and below. A few spikes a day is normal. A trace that sits high most of the day is something to take to your physician.

Stop at two weeks and decide. Keep the one or two habits that clearly helped, such as a walk after meals or an earlier last meal, and take the sensor off. If you find yourself unable to stop checking it, that is useful information too.

If your readings run high, if you see frequent lows, or if you have symptoms like unusual thirst, frequent urination or unexplained weight loss, see a physician rather than troubleshooting with diet alone.

The signal underneath the sensor

For a lot of founders, the most useful thing a CGM shows them has little to do with food: the visible cost of a short night and a stress response that stays switched on through the evening. The sensor shows the effect. The skill is changing the cause.

That is the work we do at Cinder: private 1:1 coaching that trains stress regulation and recovery as a skill, so your nervous system can actually come down after a hard day, with sessions online and practice built into your real calendar. If sleep is where your numbers suffer most, start with our wind-down protocol for executives.

Apply for private coaching

Sources

• FDA clears first over-the-counter continuous glucose monitor, U.S. Food and Drug Administration, 2024
• Continuous glucose monitoring profiles in healthy non-diabetic participants: a multicenter prospective study, Journal of Clinical Endocrinology & Metabolism (via Henry Ford Health Scholarly Commons), 2019
• National Diabetes Statistics Report, Centers for Disease Control and Prevention, 2026
• Should I use a continuous glucose monitor?, Harvard Health Publishing, 2024