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CGM medical glossary and continuous glucose monitor terminology reference

CGM Glossary: 50 Terms and Definitions

A complete reference of continuous glucose monitor terminology. Every technical, medical, metric, and regulatory term you need to understand glucose monitoring — from A1C to Time in Range — defined with clinical context and linked to related products and topics.

Understanding CGM Terminology

Continuous glucose monitoring involves a specialized vocabulary that spans biomedical engineering, clinical endocrinology, regulatory science, and digital health. Whether you are a newly diagnosed diabetes patient learning to interpret your first CGM report, a wellness user exploring over-the-counter glucose sensors, or a healthcare provider comparing devices for your patients, this glossary provides clear, clinically accurate definitions for every term you will encounter. Each entry includes related terms for cross-reference and links to the CGM products where the concept applies.

The glossary covers 50 terms across 4 categories: technical (sensor hardware, connectivity, calibration), medical (glucose physiology, diabetes, complications), metrics (MARD, time in range, GMI, coefficient of variation), and regulatory (FDA clearance, OTC classification, iCGM designation). Every definition uses precise language and quantitative data where applicable.

CGM medical glossary and glucose monitoring terminology dictionary

All Terms (A-Z)

A

  • A1C(HbA1c)— Hemoglobin A1C is a blood test that measures the percentage of hemoglobin proteins coated with sugar, reflecting average blood glucose levels over the previous 2 to 3 months.
  • Adjunctive vs Non-Adjunctive— A regulatory classification that determines whether a CGM can be used as the sole basis for treatment decisions.
  • Ambulatory Glucose Profile(AGP)— A standardized one-page glucose report recommended by the International Diabetes Center that summarizes 14 days of CGM data into a visual profile showing median glucose, interquartile range (25th to 75th percentile), and 10th to 90th percentile bands across a 24-hour period.
  • Average Daily Risk Range(ADRR)— A CGM-derived metric that predicts the risk of extreme glucose events by analyzing the daily minimum and maximum glucose values over a multi-day period.

B

  • Basal Metabolic Rate(BMR)— The minimum number of calories the body burns at complete rest to maintain essential physiological functions such as breathing, circulation, and cell repair.
  • Beta Cell— The insulin-producing cells located in the islets of Langerhans within the pancreas, responsible for sensing blood glucose levels and secreting the appropriate amount of insulin to maintain glucose homeostasis.

C

  • C-Peptide— A protein fragment released by the pancreas in a 1:1 ratio with insulin during the conversion of proinsulin to active insulin.
  • Calibration— The process of verifying and adjusting CGM accuracy by comparing a sensor reading against a traditional fingerstick blood glucose measurement.
  • Closed-Loop System— An automated insulin delivery (AID) system that combines a real-time CGM with an insulin pump and a control algorithm to automatically adjust basal insulin delivery based on predicted glucose trends.
  • Coefficient of Variation(CV)— A standardized measure of glucose variability calculated as the standard deviation of glucose values divided by the mean glucose, multiplied by 100, expressed as a percentage.
  • Continuous Glucose Monitor(CGM)— A wearable medical device that tracks glucose levels in interstitial fluid 24 hours a day through a tiny sensor inserted just under the skin.

D

  • Dawn Phenomenon— A natural rise in blood glucose that occurs between approximately 3:00 AM and 8:00 AM, triggered by the body's circadian release of cortisol, growth hormone, and other counter-regulatory hormones that stimulate hepatic glucose production.
  • Diabetic Ketoacidosis(DKA)— A life-threatening medical emergency that occurs when severe insulin deficiency causes the body to break down fat at an accelerated rate, producing ketones that accumulate in the blood and make it dangerously acidic (pH below 7.
  • Diabetic Retinopathy— Progressive damage to the blood vessels of the retina caused by chronic hyperglycemia, representing the leading cause of blindness in working-age adults (ages 20 to 74).

E

  • Electrochemical Sensor— A CGM sensor technology that uses a glucose oxidase enzyme coating on a thin filament to generate an electrical current proportional to the glucose concentration in interstitial fluid.

F

  • Fasting Insulin— The blood insulin level measured after 8 to 12 hours without food, reflecting the baseline insulin output needed to maintain glucose homeostasis.
  • FDA Clearance— The regulatory approval pathway for CGM devices in the United States, typically through the FDA's 510(k) process, which requires the manufacturer to demonstrate that a new device is substantially equivalent to an existing legally marketed device.
  • Flash Glucose Monitoring(FGM)— A type of glucose monitoring that stores continuous glucose data on the sensor but requires the user to scan the sensor with a smartphone or dedicated reader to view the current reading and recent trend data.
  • Fluorescence Sensor— A CGM sensor technology that measures glucose by detecting changes in fluorescent light emitted by a glucose-sensitive chemical compound.

G

  • Gluconeogenesis— A metabolic pathway in which the liver produces glucose from non-carbohydrate sources, including amino acids, lactate, and glycerol.
  • Glucose Management Indicator(GMI)— An estimated A1C value calculated from CGM mean glucose data, allowing users to track their A1C-equivalent in real time without requiring a laboratory blood draw.
  • Glucose Transporter(GLUT)— A family of membrane proteins that transport glucose across cell membranes, with 14 identified isoforms serving different tissues and functions.
  • Glucose Variability Index(GVI)— A composite score that combines the standard deviation and mean glucose of CGM data to quantify overall glycemic instability on a single scale.
  • Glycemic Index(GI)— A 0-to-100 scale that ranks carbohydrate-containing foods by how quickly they raise blood glucose compared to pure glucose (GI = 100).
  • Glycemic Load(GL)— A metric that accounts for both the quality and quantity of carbohydrates in a food serving, calculated as GI multiplied by grams of carbohydrates per serving divided by 100.
  • Glycemic Risk Assessment Diabetes Equation(GRADE)— A composite glucose control score derived from CGM data that separately weights time spent in hypoglycemia, euglycemia (target range), and hyperglycemia to produce a single numerical summary of glycemic risk.
  • Glycemic Variability— The magnitude and frequency of blood glucose fluctuations over a defined period.
  • Glycogen— The stored form of glucose found primarily in the liver (approximately 100 grams) and skeletal muscles (approximately 400 grams).

H

  • HOMA-IR(HOMA-IR)— Homeostatic Model Assessment of Insulin Resistance, calculated as fasting insulin (μU/mL) multiplied by fasting glucose (mg/dL) divided by 405.
  • Hyperglycemia— Abnormally high blood glucose, generally defined as levels above 180 mg/dL after meals or above 130 mg/dL fasting.
  • Hypoglycemia— Dangerously low blood glucose, generally defined as levels below 70 mg/dL, with severe hypoglycemia occurring below 54 mg/dL.

I

  • Insulin Resistance— A metabolic condition in which the body's cells respond poorly to the hormone insulin, forcing the pancreas to produce progressively larger amounts to maintain normal blood glucose levels.
  • Insulin Sensitivity— A measure of how effectively the body's cells respond to insulin to take up glucose from the bloodstream, representing the opposite end of the spectrum from insulin resistance.
  • Interstitial Fluid(ISF)— The fluid that surrounds cells in body tissue, where CGM sensors measure glucose concentration.

M

  • Macronutrients— The three categories of nutrients that provide calories and energy: carbohydrates (4 cal/g), proteins (4 cal/g), and fats (9 cal/g).
  • MARD(MARD)— Mean Absolute Relative Difference, the gold standard metric used to evaluate CGM sensor accuracy.
  • Mean Glucose— The arithmetic average of all glucose readings over a specified period, calculated from the 288 or more daily readings that most CGMs capture (one reading every 5 minutes).
  • Metabolic Syndrome(MetS)— A cluster of 5 interrelated conditions — elevated waist circumference, high triglycerides, low HDL cholesterol, high blood pressure, and high fasting glucose — that together increase the risk of cardiovascular disease by 2x and type 2 diabetes by 5x.
  • Microalbuminuria— The presence of small amounts of albumin protein in the urine (30 to 300 mg/day), serving as the earliest detectable sign of diabetic kidney damage (diabetic nephropathy).

N

  • Net Carbs— Total carbohydrates minus fiber and sugar alcohols, representing the carbohydrate content that directly impacts blood glucose levels.

O

  • Oral Glucose Tolerance Test(OGTT)— A diagnostic test in which the patient drinks a 75-gram glucose solution after fasting, with blood glucose measured at 0, 1, and 2 hours to evaluate glucose metabolism.
  • Over-the-Counter CGM(OTC CGM)— A continuous glucose monitor that can be purchased directly by consumers without a prescription, representing a new regulatory category established by the FDA in 2024.

P

  • Peripheral Neuropathy— Nerve damage caused by chronic high blood glucose that affects approximately 50% of people with diabetes over their lifetime, most commonly starting in the feet and hands with symptoms of numbness, tingling, burning pain, and loss of sensation.
  • Postprandial Glucose— Blood glucose levels measured after eating, typically peaking 60 to 90 minutes after a meal and returning to baseline within 2 to 3 hours in healthy individuals.

R

  • Real-Time CGM(RT-CGM)— A continuous glucose monitor that automatically and continuously transmits glucose readings to a display device — such as a smartphone, smartwatch, or insulin pump — without requiring the user to scan or interact with the sensor.
  • Resistant Starch— A type of starch that resists digestion in the small intestine and passes to the large intestine intact, where it functions like soluble fiber and is fermented by gut bacteria into beneficial short-chain fatty acids.

S

  • Sensor Warmup— The required initialization period after inserting a new CGM sensor before it begins delivering glucose readings.
  • Standard Deviation of Glucose(SD)— A statistical measure of how widely glucose values are spread around the mean glucose over a given period.

T

  • Time in Range(TIR)— The percentage of time a person's glucose level remains within a defined target range, typically 70 to 180 mg/dL for most people with diabetes.
  • Transmitter— The reusable electronic component that attaches to a CGM sensor and wirelessly sends glucose data to a smartphone, smartwatch, or dedicated receiver via Bluetooth.

Technical Terms

Core hardware and software terms — how CGM sensors, transmitters, and connectivity work at a technical level.

Continuous Glucose Monitor(CGM)

A wearable medical device that tracks glucose levels in interstitial fluid 24 hours a day through a tiny sensor inserted just under the skin. Most CGMs report readings every 1 to 5 minutes and transmit data wirelessly to a smartphone app or dedicated receiver. Devices like the Dexcom G7, Abbott FreeStyle Libre 3, and Senseonics Eversense E3 are the leading CGMs available in 2026.

Interstitial Fluid(ISF)

The fluid that surrounds cells in body tissue, where CGM sensors measure glucose concentration. Interstitial fluid glucose levels lag behind blood glucose by approximately 5 to 15 minutes because glucose must diffuse from capillaries into the surrounding tissue before the sensor detects it. This physiological lag is the primary reason CGM readings can differ from a fingerstick blood glucose test taken at the same moment.

Electrochemical Sensor

A CGM sensor technology that uses a glucose oxidase enzyme coating on a thin filament to generate an electrical current proportional to the glucose concentration in interstitial fluid. The enzyme catalyzes a reaction that produces hydrogen peroxide, which is measured as an electrical signal and converted into a glucose reading. Dexcom and Abbott use electrochemical sensing in all of their CGM product lines.

Fluorescence Sensor

A CGM sensor technology that measures glucose by detecting changes in fluorescent light emitted by a glucose-sensitive chemical compound. Unlike electrochemical sensors, fluorescence-based sensors do not consume glucose during measurement, which contributes to longer sensor life. Senseonics uses this technology in its Eversense line of implantable CGMs, enabling sensor durations of up to 365 days.

Transmitter

The reusable electronic component that attaches to a CGM sensor and wirelessly sends glucose data to a smartphone, smartwatch, or dedicated receiver via Bluetooth. Transmitters are typically rechargeable or have a fixed battery life spanning several months. On the Dexcom G7, the transmitter is integrated into the disposable sensor pod, while the Eversense system uses a separate rechargeable transmitter worn over the implanted sensor.

Sensor Warmup

The required initialization period after inserting a new CGM sensor before it begins delivering glucose readings. Warmup times vary by device: the Dexcom G7 requires approximately 30 minutes, the FreeStyle Libre 3 requires 60 minutes, and older models like the Dexcom G6 required up to 2 hours. During warmup, the sensor stabilizes in interstitial fluid and the device runs internal calibration algorithms.

Calibration

The process of verifying and adjusting CGM accuracy by comparing a sensor reading against a traditional fingerstick blood glucose measurement. Older CGM systems required 2 calibrations per day, but most modern devices — including the Dexcom G7 and FreeStyle Libre 3 — are factory-calibrated at the manufacturing facility and require zero fingerstick calibrations during use. The Eversense E3 still requires 1 calibration per day for optimal accuracy.

Flash Glucose Monitoring(FGM)

A type of glucose monitoring that stores continuous glucose data on the sensor but requires the user to scan the sensor with a smartphone or dedicated reader to view the current reading and recent trend data. The FreeStyle Libre 2 is the primary example of flash glucose monitoring. Unlike real-time CGMs, flash monitors do not automatically push alerts for high or low glucose events unless actively scanned, though newer models like the Libre 3 have transitioned to full real-time monitoring.

Real-Time CGM(RT-CGM)

A continuous glucose monitor that automatically and continuously transmits glucose readings to a display device — such as a smartphone, smartwatch, or insulin pump — without requiring the user to scan or interact with the sensor. Real-time CGMs provide proactive high and low glucose alerts, making them essential for people on insulin therapy. The Dexcom G7, FreeStyle Libre 3, and Eversense E3 are all classified as real-time CGMs.

Closed-Loop System

An automated insulin delivery (AID) system that combines a real-time CGM with an insulin pump and a control algorithm to automatically adjust basal insulin delivery based on predicted glucose trends. Closed-loop systems reduce the burden of manual insulin dosing and have been shown in clinical trials to increase time in range by 10 to 15 percentage points compared to manual pump therapy. Leading systems include the Medtronic 780G, Tandem t:slim X2 with Control-IQ, and Omnipod 5, all of which integrate with Dexcom G7 CGM data.

Medical Terms

Clinical and physiological terms related to glucose metabolism, diabetes, and the medical conditions that CGMs help manage.

A1C(HbA1c)

Hemoglobin A1C is a blood test that measures the percentage of hemoglobin proteins coated with sugar, reflecting average blood glucose levels over the previous 2 to 3 months. An A1C below 5.7% is considered normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher confirms a diabetes diagnosis. CGM data can now estimate A1C through the Glucose Management Indicator (GMI), allowing patients to track their A1C-equivalent in real time without a blood draw.

Hyperglycemia

Abnormally high blood glucose, generally defined as levels above 180 mg/dL after meals or above 130 mg/dL fasting. Common causes include insufficient insulin, illness, emotional stress, excess carbohydrate intake, and certain medications like corticosteroids. CGMs provide real-time high glucose alerts that allow users to take corrective action — such as administering insulin or going for a walk — before levels climb to dangerous thresholds above 250 mg/dL.

Hypoglycemia

Dangerously low blood glucose, generally defined as levels below 70 mg/dL, with severe hypoglycemia occurring below 54 mg/dL. Symptoms include shakiness, sweating, confusion, rapid heartbeat, and in severe cases, seizures or loss of consciousness. CGMs with predictive low glucose alerts — such as the Dexcom G7 urgent low alarm at 55 mg/dL — can warn users 20 minutes before glucose drops to dangerous levels, significantly reducing the frequency and severity of hypoglycemic episodes.

Insulin Resistance

A metabolic condition in which the body's cells respond poorly to the hormone insulin, forcing the pancreas to produce progressively larger amounts to maintain normal blood glucose levels. Insulin resistance affects an estimated 40% of US adults aged 18 to 44 and is the primary driver of type 2 diabetes, metabolic syndrome, and nonalcoholic fatty liver disease. CGM data can reveal insulin resistance through patterns such as prolonged postprandial glucose elevation lasting more than 3 hours, elevated fasting glucose, and high glycemic variability.

Glycemic Variability

The magnitude and frequency of blood glucose fluctuations over a defined period. High glycemic variability — characterized by frequent spikes and drops — is associated with increased oxidative stress, cardiovascular risk, and diabetes complications independent of average glucose or A1C. A coefficient of variation (CV) below 36% is the recommended target for stable glucose control, and CGMs are the only practical tool that can measure glycemic variability continuously across days and weeks.

Postprandial Glucose

Blood glucose levels measured after eating, typically peaking 60 to 90 minutes after a meal and returning to baseline within 2 to 3 hours in healthy individuals. A postprandial spike above 140 mg/dL may indicate impaired glucose tolerance, while consistent spikes above 180 mg/dL suggest inadequate insulin action. CGMs uniquely reveal how different foods, portion sizes, and meal compositions affect an individual's glucose response — data that fingerstick tests taken at a single point in time cannot capture.

Dawn Phenomenon

A natural rise in blood glucose that occurs between approximately 3:00 AM and 8:00 AM, triggered by the body's circadian release of cortisol, growth hormone, and other counter-regulatory hormones that stimulate hepatic glucose production. The dawn phenomenon affects up to 50% of people with diabetes and can raise fasting glucose by 20 to 40 mg/dL. CGMs make the dawn phenomenon clearly visible on overnight glucose graphs, helping clinicians adjust basal insulin timing or medication dosing to address early-morning highs.

Diabetic Ketoacidosis(DKA)

A life-threatening medical emergency that occurs when severe insulin deficiency causes the body to break down fat at an accelerated rate, producing ketones that accumulate in the blood and make it dangerously acidic (pH below 7.3). DKA primarily affects people with type 1 diabetes and is characterized by blood glucose above 250 mg/dL, blood ketones above 3.0 mmol/L, nausea, abdominal pain, and fruity-smelling breath. CGMs with high glucose alerts help prevent DKA by warning users when glucose exceeds 250 mg/dL, enabling early intervention before ketone levels become dangerous.

Peripheral Neuropathy

Nerve damage caused by chronic high blood glucose that affects approximately 50% of people with diabetes over their lifetime, most commonly starting in the feet and hands with symptoms of numbness, tingling, burning pain, and loss of sensation. Peripheral neuropathy results from glucose-mediated damage to small blood vessels that supply nerves, and it progresses silently — often detected only after significant nerve loss. CGM-guided glucose management that maintains time in range above 70% has been shown to slow neuropathy progression by reducing the glycemic variability that accelerates nerve damage.

Diabetic Retinopathy

Progressive damage to the blood vessels of the retina caused by chronic hyperglycemia, representing the leading cause of blindness in working-age adults (ages 20 to 74). Diabetic retinopathy progresses through stages from mild nonproliferative (microaneurysms) to proliferative (abnormal new blood vessel growth) and can cause vision loss from macular edema or retinal detachment. The DCCT trial demonstrated that intensive glucose control reduces retinopathy risk by 76%, and CGMs facilitate the tight glucose management needed to prevent or slow progression.

Microalbuminuria

The presence of small amounts of albumin protein in the urine (30 to 300 mg/day), serving as the earliest detectable sign of diabetic kidney damage (diabetic nephropathy). Healthy kidneys filter albumin back into the blood, but high blood glucose damages the glomerular filtration barrier over time, allowing albumin to leak into urine. Screening for microalbuminuria is recommended annually for all diabetes patients, and CGM-guided glucose control with time in range above 70% significantly reduces the risk of progression to overt nephropathy.

Glucose Transporter(GLUT)

A family of membrane proteins that transport glucose across cell membranes, with 14 identified isoforms serving different tissues and functions. GLUT4 is the insulin-dependent transporter found primarily in muscle and fat cells — when insulin binds its receptor, GLUT4 moves to the cell surface to allow glucose entry, which is the mechanism impaired in insulin resistance. GLUT1 provides constant glucose transport to the brain, while GLUT2 in the liver and pancreatic beta cells acts as a glucose sensor that regulates insulin secretion.

Metrics & Measurements

The quantitative measurements derived from continuous glucose monitoring data, used by clinicians and patients to assess glucose control.

MARD(MARD)

Mean Absolute Relative Difference, the gold standard metric used to evaluate CGM sensor accuracy. MARD is calculated by comparing CGM readings against simultaneous laboratory blood glucose measurements and expressing the average percentage difference. A lower MARD indicates higher accuracy — the best CGMs in 2026 achieve MARD values between 7% and 9%, with the Dexcom G7 at 8.2% and the FreeStyle Libre 3 at 7.9%. A MARD above 10% is generally considered less reliable for insulin dosing decisions.

Time in Range(TIR)

The percentage of time a person's glucose level remains within a defined target range, typically 70 to 180 mg/dL for most people with diabetes. International consensus guidelines recommend a TIR target of greater than 70% (approximately 16 hours and 48 minutes per day) for most adults with type 1 or type 2 diabetes. Each 5% increase in TIR corresponds to a clinically meaningful A1C reduction of approximately 0.5%, making TIR the preferred metric for assessing glucose control from CGM data.

Glucose Management Indicator(GMI)

An estimated A1C value calculated from CGM mean glucose data, allowing users to track their A1C-equivalent in real time without requiring a laboratory blood draw. GMI is calculated using the formula: GMI (%) = 3.31 + (0.02392 × mean glucose in mg/dL). While GMI correlates well with laboratory A1C at a population level, individual discrepancies of 0.3% to 0.5% can occur due to differences in red blood cell lifespan and hemoglobin glycation rates.

Coefficient of Variation(CV)

A standardized measure of glucose variability calculated as the standard deviation of glucose values divided by the mean glucose, multiplied by 100, expressed as a percentage. A CV below 36% is the internationally recommended target indicating stable glucose control, while values above 36% signal problematic glucose variability that increases the risk of both hyperglycemia and hypoglycemia. CV is considered more reliable than standard deviation alone because it adjusts for differences in mean glucose levels between individuals.

Ambulatory Glucose Profile(AGP)

A standardized one-page glucose report recommended by the International Diabetes Center that summarizes 14 days of CGM data into a visual profile showing median glucose, interquartile range (25th to 75th percentile), and 10th to 90th percentile bands across a 24-hour period. The AGP report also includes key metrics such as time in range, time above range, time below range, GMI, CV, and mean glucose. Clinicians use AGP reports to identify glucose patterns — such as consistent post-lunch spikes or overnight lows — and adjust treatment accordingly.

Glucose Variability Index(GVI)

A composite score that combines the standard deviation and mean glucose of CGM data to quantify overall glycemic instability on a single scale. A GVI of 1.0 represents perfectly stable glucose, values below 1.2 indicate low variability, 1.2 to 1.5 indicate moderate variability, and values above 1.5 indicate high variability requiring clinical attention. GVI provides a more intuitive summary of glucose stability than coefficient of variation alone because it weights both the amplitude and frequency of glucose fluctuations.

Mean Glucose

The arithmetic average of all glucose readings over a specified period, calculated from the 288 or more daily readings that most CGMs capture (one reading every 5 minutes). Mean glucose is a core input for calculating the Glucose Management Indicator (GMI) and correlates with A1C, though the relationship is not perfectly linear for all individuals. A mean glucose of 154 mg/dL corresponds to an estimated A1C of approximately 7.0%, and each 25 mg/dL increase in mean glucose raises estimated A1C by roughly 0.5%.

Standard Deviation of Glucose(SD)

A statistical measure of how widely glucose values are spread around the mean glucose over a given period. A lower standard deviation indicates more stable glucose with smaller fluctuations, while a higher SD reflects wider swings between highs and lows. For most adults with diabetes, an SD below one-third of the mean glucose is considered a reasonable target. SD is used alongside the coefficient of variation (CV = SD ÷ mean × 100) to assess glycemic variability from CGM data.

Glycemic Risk Assessment Diabetes Equation(GRADE)

A composite glucose control score derived from CGM data that separately weights time spent in hypoglycemia, euglycemia (target range), and hyperglycemia to produce a single numerical summary of glycemic risk. Unlike mean glucose or A1C, GRADE assigns disproportionately higher risk scores to extreme glucose values, making it more sensitive to dangerous highs and lows. A GRADE score below 5 indicates excellent control, while scores above 10 suggest significant glycemic dysfunction requiring intervention.

Average Daily Risk Range(ADRR)

A CGM-derived metric that predicts the risk of extreme glucose events by analyzing the daily minimum and maximum glucose values over a multi-day period. ADRR accounts for both hypoglycemic and hyperglycemic risk on a single scale: values below 20 indicate low risk, 20 to 40 indicate moderate risk, and values above 40 indicate high risk of dangerous glucose excursions. ADRR is clinically valuable because it captures the extremes of glucose behavior that averages and standard deviations may mask.

Regulatory Terms

FDA classifications, approval pathways, and regulatory designations that determine how CGMs can be marketed and sold.

FDA Clearance

The regulatory approval pathway for CGM devices in the United States, typically through the FDA's 510(k) process, which requires the manufacturer to demonstrate that a new device is substantially equivalent to an existing legally marketed device. FDA clearance evaluates safety and accuracy data — including MARD performance in clinical trials — before a CGM can be sold in the US. As of 2026, every CGM sold in the United States from Dexcom, Abbott, and Senseonics has received FDA clearance, and the FDA has created a new regulatory pathway specifically for over-the-counter CGMs.

Over-the-Counter CGM(OTC CGM)

A continuous glucose monitor that can be purchased directly by consumers without a prescription, representing a new regulatory category established by the FDA in 2024. Over-the-counter CGMs are intended for general wellness and glucose awareness in people without diabetes, not for insulin dosing decisions. The Dexcom Stelo and Abbott Lingo were among the first OTC CGMs to reach the market, priced between $89 and $99 per month without insurance, and they cannot be used with insulin pumps or for closed-loop systems.

Adjunctive vs Non-Adjunctive

A regulatory classification that determines whether a CGM can be used as the sole basis for treatment decisions. Adjunctive CGMs require the user to confirm readings with a traditional fingerstick blood glucose test before making insulin dosing or treatment decisions. Non-adjunctive (also called iCGM or integrated CGM) devices like the Dexcom G7 and FreeStyle Libre 3 have demonstrated sufficient accuracy to replace fingerstick testing entirely for treatment decisions, including insulin dosing. The FDA's iCGM classification, introduced in 2018, codified the accuracy standards required for non-adjunctive use.