When Glucose Monitors Fail: The Hidden Dangers for Diabetics

Key Takeaways

• Glucose monitor malfunctions, like false highs, false lows, or missed alarms, can lead to severe hypoglycemia, hyperglycemia, or even DKA.
• Recent recalls, FDA warnings, and adverse event reports highlight recurring risks with continuous glucose monitors.
• Preserving device data, medical records, and filing reports with the FDA can help protect both health and legal rights.
• If a faulty glucose monitor caused you harm, contact Morgan & Morgan to explore your legal options and pursue compensation.

Continuous glucose monitors (CGMs) and blood-glucose meters have revolutionized diabetes care. They let people see trends in real time, detect overnight lows, and, when paired with insulin pumps, can automatically adjust therapy. 

But like any medical device, glucose monitors are not infallible. 

Sensor errors, software bugs, connectivity problems, receiver failures, and even inappropriate use of non-approved wearables can produce inaccurate readings that put patients at real risk of severe hypoglycemia, hyperglycemia, diabetic ketoacidosis (DKA), and other harms. 

Below, we will explore the real-world dangers when monitoring devices malfunction, recent regulatory concerns and recalls, and what victims should do next, including legal options if a defective device caused injury.

How Glucose Monitors Work and How They Can Go Wrong

Most modern CGMs measure glucose in the interstitial fluid beneath the skin via a tiny sensor and translate that into a blood-glucose estimate reported every few minutes. 

That process depends on chemistry (enzymes on a sensor), electronics, algorithms that convert measurements into numbers, and often a phone or receiver to display readings and alert the user.

Because CGMs are complex systems, failures can occur at multiple points, such as:

• Sensor chemistry or manufacturing defects — an improperly manufactured sensor can drift or produce biased readings.
• Algorithm/software errors — firmware or app bugs can miscalculate or misdisplay values or suppress alarms.
• Hardware failures — a receiver speaker or phone connection that fails can stop critical audible alerts.
• Connectivity and smartphone settings — smartphone notification settings or Bluetooth drops can prevent alerts from reaching the user.
• Physical issues — sensor displacement, adhesive failure, or body-position pressure can cause false lows (so-called “compression lows”).
• Use of unapproved devices — non-approved smartwatches or rings claiming to measure glucose can give dangerously inaccurate estimates.

Each of these failure modes can translate into the same clinical consequences: missed low-glucose alarms, false readings that prompt incorrect insulin dosing, or false reassurance that prevents needed treatment.

The Clinical Dangers: Why a Wrong Number Can Become an Emergency

A CGM that reads falsely high or falsely low is not a harmless technical glitch. For people on insulin, decisions, like when to eat, when to inject, or when to reduce a pump rate, are often guided by device readings. Mistakes can cause:

• Severe hypoglycemia — if a CGM under-reports (false low) or a user relies solely on a faulty reading to reduce a corrective carbohydrate dose, blood sugar may fall to dangerously low levels, causing seizures, loss of consciousness, or even death. The CDC stresses that low blood sugar can be dangerous and requires prompt treatment.
• Hyperglycemia and DKA — over-reliance on a falsely low reading may cause someone to skip insulin needed to correct high glucose trends, risking prolonged hyperglycemia and potentially DKA, a life-threatening emergency.
• Mistimed insulin dosing — inaccurate spike or trough detection can cause repeated insulin dosing errors, producing wide glucose variability that increases hospitalizations and long-term complications.
• Delayed or missed emergency alerts — failures of audible alarms or smartphone notifications can prevent caregivers from intervening during nocturnal hypoglycemia. The FDA has warned that smartphone or device configurations can cause patients to miss critical safety alerts.
   

Clinical studies and device reports have documented specific mechanisms. For example, sensors compressed by body position can produce falsely low readings overnight—so-called compression lows, leading to unnecessary carbohydrate intake or, conversely, ignored alarms because they appear spurious.

Recent recalls and Regulatory Warnings 

Regulators and manufacturers have repeatedly flagged CGM issues in recent years:

• Abbott FreeStyle Libre 3 — Abbott issued recalls and voluntary corrections for certain Libre 3 sensors after reports of inaccurate high glucose readings that could cause serious injury. The FDA classified some Libre 3 sensor actions as a Class I recall, indicating the potential for severe harm.
• FDA alerts about smartphone notifications — the FDA has explicitly warned patients that smartphone settings and app configurations can prevent diabetes devices from delivering critical safety alerts and advised users to verify their settings and notification pathways. Missing these alerts can have life-threatening consequences.
• MAUDE (adverse event) reports — the FDA’s MAUDE database shows numerous event reports describing discrepancies between CGM readings and fingerstick meters, missed alarms, and sensor inaccuracies. While individual MAUDE reports do not establish causation, they show patterns of device-related problems reported by users and clinicians.
• Warnings against non-approved wearables — the FDA warns consumers that no smartwatch or ring is currently authorized to measure blood glucose without a validated invasive sensor; using unapproved devices for dosing decisions is dangerous.
  
   

Common Failure Scenarios Patients Report

Below are recurring, real-world scenarios clinicians and device investigators see repeatedly, each with potential for harm.

• False low during sleep (compression low) — a patient wakes to multiple low alerts from a CGM that are actually artifactual because pressure on the sensor changes interstitial glucose readings. Repeated false alarms can cause alarm fatigue, or cause patients to over-treat and then swing high.
• Missed audible alarm because receiver speaker failed — if an audible alarm doesn’t sound and the patient is asleep, a severe overnight hypoglycemic episode may go undetected until a roommate or family member finds them. Recent device recalls have explicitly addressed receiver speaker malfunctions.
• False high after a sensor manufacturing defect — a sensor that consistently reports high values can lead to excessive insulin dosing and subsequent hypoglycemia, or unnecessary emergency room visits and medication changes. Abbott’s Libre 3 corrections addressed some instances of inaccurate high readings.
• App notifications suppressed by smartphone settings — reliance on a phone for alert delivery can backfire if Do Not Disturb, notification silencing, or battery-saving settings prevent alerts from appearing. The FDA has warned patients to check their settings regularly.
• Use of unapproved noninvasive devices — a person using a consumer wearable that claims to estimate glucose may make treatment decisions on inaccurate data; the FDA warns against this practice.
  
   

When Is a Device Manufacturer Responsible?

When a defective glucose monitor injures a patient, multiple legal theories may apply. The exact claim will depend on state law and the facts, but common avenues include:

• Product liability (defect in design or manufacture) — if a device is defectively designed or a particular sensor batch was manufactured incorrectly, injured users may pursue claims that the product was unreasonably dangerous. Recalls and FDA findings can be powerful evidence.
• Failure to warn (inadequate instructions/labeling) — if a manufacturer failed to warn about a known risk (for example, certain adhesives failing in hot weather, or the potential for compression lows), and that omission led to injury, there may be liability.
• Negligence — claims that the manufacturer, a distributor, or a healthcare provider failed to act with reasonable care (for instance, by failing to implement proper quality controls or by not notifying users promptly after learning of a defect).
• Breach of warranty and consumer protection claims — depending on the jurisdiction, purchasers may have claims under warranty law or consumer fraud statutes.
• Class actions or mass torts — when large numbers of people are affected (for example, a model-wide recall), litigators sometimes pursue class actions or coordinated lawsuits.
• Medical malpractice (limited circumstances) — if a clinician relied on a device inappropriately or mismanaged a known device issue, there may be provider liability.
   

Regulatory actions (recalls, FDA safety communications, warning letters to manufacturers) can strengthen civil claims because they demonstrate that the regulator identified a problem and that the manufacturer knew or should have known of risks. For example, the FDA’s recall classification of certain Libre 3 sensors as Class I (the most serious) is highly relevant to product liability analysis.

What to Do Immediately if Your Glucose Monitor Malfunctions and You Suffer Harm

If you suspect a monitor failure caused injury, take these steps promptly. They both protect your health and preserve evidence for any later claim.

1. Seek medical care first. If you are symptomatic (seizure, fainting, severe nausea, confusion, unable to treat), go to the ER or call 911. Don’t rely solely on device readings. Treat symptoms and confirm with a fingerstick glucose check or lab test. (CGMs estimate interstitial glucose; fingertip meters and lab tests are standards for confirmatory testing.)
2. Document everything. Save the device, sensor and packaging. Take photos of the sensor placement, error messages, app screens, and any alarms. Note the date/time of the event, exactly what you were doing, what the device read, and any symptoms or treatments given.
3. Get objective medical records. Ask the treating clinician for a copy of ER records, glucose readings (fingerstick or lab), and notes describing the event. Hospital labs and clinician notes are essential to show the clinical reality of what happened versus what the CGM reported.
4. Export device/app data. Many CGM apps allow exporting a log of glucose readings, alarm history and device events. Preserve a copy (screenshots plus formal exported files). Device logs can show discrepancies between displayed trends and real blood glucose.
5. Report the problem. File a report with the manufacturer and with the FDA’s MedWatch (or the appropriate regulatory body in your country). Reporting helps regulators spot patterns and is useful evidence in legal claims. MAUDE is the FDA database where many adverse events are logged. FDA Access Data
6. Don’t throw away the device or sensor. Even if the device seems broken, keep it in a safe place—manufacturers or investigators may request the physical item for testing.
7. Contact an experienced attorney. If you suffered serious injury or incurred medical costs because of a malfunctioning device, consult counsel experienced in product liability and medical device litigation promptly. Statutes of limitations and preservation obligations vary by state; acting quickly preserves legal options.
   
    

Evidence That Helps a Legal Case

Successful claims often rely on a combination of clinical and technical evidence:

• Medical records and laboratory glucose values proving actual hypo/hyperglycemia.
• Device and app logs that show readings and alarm history.
• The physical sensor/receiver and packaging (lot numbers, serial numbers).
• Photos and contemporaneous notes from the injured person or caregivers.
• Manufacturer recall notices, FDA safety communications, and MAUDE reports showing pattern or notice to the manufacturer.
• Expert opinions from endocrinologists, biomedical engineers, or device-testing labs linking the malfunction to the injury.
   

Remember, regulatory documents, such as recalls, FDA safety alerts, warning letters, are powerful evidence because they show that a device or manufacturing practice posed a recognized hazard.

What Courts and Juries Consider

Courts and juries look at whether the device performed as intended, whether the manufacturer knew about the risk, what warnings were provided, and whether the injured person used the device as directed. A documented recall or an FDA warning makes it more likely a jury will find the manufacturer knew of the risk. Conversely, defense lawyers often point to user error, improper insertion, or failure to obtain confirmatory fingerstick readings as reasons the device did not cause the harm, so good documentation is very important.

Prevention Steps Users and Clinicians Can Take Now

Device failures will never be zero, but risks are reduced by sensible practices:

• Confirm suspicious readings with a fingerstick meter or lab test before making major insulin adjustments. CGMs are powerful tools—but when in doubt, confirm.
• Keep phone and app settings checked. Ensure critical alerts are allowed to bypass Do Not Disturb, check battery-saving settings, and test alarm volume regularly. The FDA has advised users to review device-app notification settings. U.S. Food and Drug Administration
• Rotate sensor sites and watch for compression. Avoid sleeping positions that press on the sensor and rotate insertion sites per manufacturer guidance.
• Follow recall notices and manufacturer instructions if a recall or correction is issued: stop using affected lot numbers and follow replacement instructions. U.S. Food and Drug Administration+1
• Avoid unapproved noninvasive devices for dosing decisions; the FDA warns such devices are not substitutes for approved CGMs. U.S. Food and Drug Administration

How Morgan & Morgan Can Help

When a glucose monitor fails and someone is hurt, injured patients need a law firm that can make the difference in the fight for justice and compensation.

A firm experienced in product liability and medical device litigation can evaluate whether design defects, manufacturing problems, or inadequate warnings are to blame—and fight for the full and fair compensation you need and deserve to move forward with your life.

Glucose monitors have greatly improved diabetes self-management, reduced the burden of frequent fingersticks, and prevented countless emergencies, but they are not risk-free. When a monitor fails, through manufacturing error, software bug, hardware defect, or simple connectivity issues, the consequences can be severe. 

If you or a loved one was injured because a glucose monitor gave inaccurate readings or failed to alert, document everything, seek medical care, report the event to the manufacturer and the FDA, and contact an experienced attorney at Morgan & Morgan to discuss whether you have a product liability claim.