Continuous Glucose Monitor Without a Prescription

What is a CGM and how does it work?

A continuous glucose monitor is a small sensor worn on the back of the upper arm or abdomen. A tiny filament sits just under the skin and measures glucose in the interstitial fluid — the fluid surrounding cells — every few minutes. The sensor transmits readings wirelessly to a smartphone app, displaying a real-time glucose trend rather than a single snapshot.

This is different from a traditional fingerstick glucose meter, which gives a reading at one moment in time. A CGM shows the shape of your glucose curve — how quickly it rises after eating, how high it peaks, how long it takes to return toward baseline, and what it does during sleep. Because CGMs measure interstitial fluid rather than blood directly, readings can lag behind blood glucose by approximately 5 to 15 minutes during rapid changes such as intense exercise 1Ref 1American Diabetes Association Professional Practice Committee (2024).2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2024.Postprandial glucose thresholds for diabetes and prediabetes; standard laboratory tests required for diagnosis; CGM technology characteristics including interstitial fluid lag.

Which CGMs are available without a prescription?

In 2024, the FDA cleared the first CGMs specifically for over-the-counter sale to adults without a diabetes diagnosis. In March 2024, Dexcom's Stelo Glucose Biosensor System became the first OTC CGM cleared for adults 18 and older who do not use insulin. In June 2024, Abbott received clearance for two OTC devices: the Lingo (a general wellness monitor for adults without diabetes) and the Libre Rio (for adults with type 2 diabetes not using insulin) 2Ref 2U.S. Food and Drug Administration (2024).FDA Clears First Over-the-Counter Continuous Glucose Monitor.FDA clearance of first OTC CGMs in 2024 for adults without diabetes — Dexcom Stelo (March 2024) and Abbott Lingo/Libre Rio (June 2024).

OTC CGMs typically work for a defined sensor wear period (often 14 days) and are available at major pharmacies and online. Prescription-only CGMs designed for intensive diabetes management — including insulin dosing decisions — remain separate products with different accuracy requirements 2Ref 2U.S. Food and Drug Administration (2024).FDA Clears First Over-the-Counter Continuous Glucose Monitor.FDA clearance of first OTC CGMs in 2024 for adults without diabetes — Dexcom Stelo (March 2024) and Abbott Lingo/Libre Rio (June 2024).

Who might benefit from using a CGM without diabetes?

People most likely to find a CGM informative include:

• Those with prediabetes or insulin resistance who want to understand how their glucose responds to different foods and activities
• People with a strong family history of diabetes who want early visibility into their glucose patterns
• Those experiencing symptoms suggestive of glucose dysregulation — energy crashes, post-meal fatigue, difficulty concentrating after eating
• People making dietary changes and wanting objective feedback on how choices affect blood sugar

A CGM does not diagnose diabetes — that requires standardized laboratory testing (fasting glucose, HbA1c, or oral glucose tolerance test), not a wearable device 1Ref 1American Diabetes Association Professional Practice Committee (2024).2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2024.Postprandial glucose thresholds for diabetes and prediabetes; standard laboratory tests required for diagnosis; CGM technology characteristics including interstitial fluid lag. However, CGM data can motivate meaningful behavior change and give a clinician useful patterns to guide the conversation.

What does normal glucose data look like on a CGM?

For adults without diabetes, fasting glucose (overnight) typically stays in the range of roughly 70 to 100 mg/dL. After meals, glucose rises and then returns toward the fasting range. The ADA defines postprandial thresholds: prediabetes is 140–199 mg/dL at two hours; diabetes is 200 mg/dL or higher 1Ref 1American Diabetes Association Professional Practice Committee (2024).2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2024.Postprandial glucose thresholds for diabetes and prediabetes; standard laboratory tests required for diagnosis; CGM technology characteristics including interstitial fluid lag.

On a CGM, you will see considerable individual variation. Some people have steep rises and rapid returns; others have flatter curves. A meal that briefly spikes glucose to 160 mg/dL and returns to baseline within two hours may be less concerning than one that keeps glucose elevated for three or four hours. However, the clinical significance of various CGM patterns in people without diabetes is still an active area of research — population-level thresholds established in diabetes trials do not directly translate to non-diabetic individuals.

If you consistently see readings above 140 at one to two hours after meals, that is worth discussing with a clinician — it likely warrants formal glucose testing 1Ref 1American Diabetes Association Professional Practice Committee (2024).2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2024.Postprandial glucose thresholds for diabetes and prediabetes; standard laboratory tests required for diagnosis; CGM technology characteristics including interstitial fluid lag.

What are the limitations of OTC CGMs?

A few important caveats:

• Interstitial fluid lag. CGMs measure glucose in fluid surrounding cells, not directly in blood. During rapid changes — intense exercise, treating a low — the reading may trail the true blood level by 5–15 minutes 1Ref 1American Diabetes Association Professional Practice Committee (2024).2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2024.Postprandial glucose thresholds for diabetes and prediabetes; standard laboratory tests required for diagnosis; CGM technology characteristics including interstitial fluid lag.
• Individual variation is large. The same food can spike one person's glucose significantly and barely move another's. What your CGM shows reflects your biology, not a universal response.
• More data is not always better without guidance. Watching glucose numbers obsessively can generate anxiety without improving health. The goal is to identify patterns, not to chase every number.
• OTC CGMs are not for insulin dosing. If you use insulin or have established diabetes, you need a clinician-supervised CGM system with appropriate accuracy specifications, not an OTC wellness device 2Ref 2U.S. Food and Drug Administration (2024).FDA Clears First Over-the-Counter Continuous Glucose Monitor.FDA clearance of first OTC CGMs in 2024 for adults without diabetes — Dexcom Stelo (March 2024) and Abbott Lingo/Libre Rio (June 2024).

How a Gale clinician can help

If you have been using a CGM and see patterns that concern you — persistent overnight elevations, consistent post-meal spikes above 140, or unexplained lows — a Gale primary care clinician can review that data alongside formal glucose testing (HbA1c or fasting glucose) and your full health picture. They can determine whether what your CGM is showing represents a clinical concern or normal biological variation.