When your Dexcom G6 or G7 CGM gives a wrong reading — what does that mean for your health?

Many people living with diabetes rely on their continuous glucose monitor every single day. For some, a faulty or misread result led to a dangerous insulin dose, a missed hypoglycaemic episode, or a hospitalisation that felt entirely preventable. Understanding how these devices work — and where the system around them can fail — is the first step to making sense of what happened to you.

Understanding the Dexcom G6 and G7: what they are and what they normally do

A continuous glucose monitor, or CGM, is a small wearable device that measures glucose levels in the fluid just beneath the skin. Unlike a traditional finger-prick test, a CGM reads glucose every few minutes and sends the result to a receiver, smartphone, or smartwatch. The Dexcom G6 and G7 are two of the most widely used CGM systems in Australia.

The G6 uses a sensor worn on the abdomen or upper arm. A tiny filament sits just under the skin and measures interstitial glucose — the glucose in the fluid surrounding cells, not directly in the blood. The G7 is a newer, smaller device that integrates the transmitter and sensor into one unit, making it easier to apply. Both devices send readings every five minutes and can trigger alarms when glucose drops too low or rises too high.

How the readings reach you

The sensor sends a signal to a transmitter, which passes the data to a paired device. The Dexcom app or receiver then displays a glucose number alongside a trend arrow showing whether levels are rising, falling, or stable. That trend arrow is often just as important as the number itself — a reading of 6.0 mmol/L with a rapidly falling arrow means something very different from a stable 6.0.

Clinicians use CGM data to adjust insulin doses, identify patterns, and make treatment decisions. Endocrinologists, diabetes educators, and GPs all rely on this data. When a patient shares their CGM report at an appointment, the clinician is expected to interpret it carefully and act on what it shows.

For more general information about diabetes management and glucose monitoring, Healthdirect Australia provides a reliable starting point.

When things start to go wrong — warning signs with CGM readings

CGM devices are accurate for most people most of the time. But several situations can cause readings to drift from reality, and some of those situations are predictable and well-documented.

The device itself will sometimes flag a problem — displaying a “Signal Loss” message, a “Sensor Error,” or a prompt to check blood glucose with a finger-prick test. But not every inaccurate reading triggers an alert. A sensor can produce a plausible-looking number that is, in fact, significantly wrong.

Patients often notice something feels off before the device does. Feeling shaky or sweaty while the CGM shows a normal reading is a recognised pattern. Dexcom’s own guidance tells users to perform a finger-prick test whenever symptoms do not match the CGM reading. A clinician who prescribes or manages CGM use should make this clear to every patient.

A common pattern — where care can break down with CGM use

The Dexcom G6 and G7 are tools. Like any tool, their value depends on how well the people using them — and the clinicians overseeing them — understand their limits. Several failure patterns appear repeatedly in situations where patients have been harmed.

Failure to educate the patient properly at the start

A clinician who prescribes a CGM carries a responsibility to explain how it works, what its limitations are, and when to override it with a finger-prick test. Many patients receive a device with minimal training. Some are never told that certain medications affect readings. Others are never warned about compression lows during sleep.

Treating CGM data as infallible during clinical review

At a diabetes review appointment, a clinician may look at a CGM report and adjust insulin doses based purely on the displayed data. If the data contains systematic errors — for example, because the patient has been placing sensors on scar tissue — those adjustments can push the patient toward hypoglycaemia or hyperglycaemia. A careful clinician cross-checks CGM data against HbA1c results and asks about symptoms.

Ignoring alarm fatigue

CGM alarms are designed to alert patients to dangerous glucose levels. Over time, frequent alarms — especially false alarms — lead patients to silence or ignore them. A clinician who reviews a patient’s CGM settings and sees that all alarms are turned off should ask why. Alarm fatigue is a documented safety issue, and addressing it is part of good diabetes management.

Delayed response to a reported sensor failure

When a patient reports that their CGM is giving readings that do not match how they feel, a clinician should take that seriously. Dismissing the concern — telling the patient to “trust the device” — can lead to dangerous decisions about insulin dosing. The Australian Commission on Safety and Quality in Health Care recognises that patient-reported concerns about medical devices deserve a structured clinical response.

Failure to act on hypoglycaemia patterns in CGM data

CGM reports show time-in-range statistics, hypoglycaemia frequency, and overnight glucose patterns. A clinician who reviews this data and fails to act on repeated low readings — particularly nocturnal lows — has missed a clear clinical signal. Repeated hypoglycaemia causes cumulative harm, including hypoglycaemia unawareness, where the body stops producing warning symptoms.

Why this matters legally

Every clinician who treats a patient owes that patient a duty of care — a legal obligation to provide treatment that meets the standard a competent clinician in the same field would reasonably provide. This duty applies to GPs, endocrinologists, diabetes educators, and any other health professional involved in managing a patient’s CGM use.

Not every bad outcome from a CGM reading amounts to a legal wrong. Devices can fail in ways that no clinician could have predicted or prevented. A single hypoglycaemic episode, even a serious one, does not automatically mean the care was inadequate. The question is whether the clinician acted as a reasonable, competent practitioner would have acted given what they knew — or should have known — at the time.

Where a clinician ignored clear warning signs in CGM data, failed to educate a patient about documented device limitations, or dismissed a patient’s concern about inaccurate readings, the picture changes. Those are failures of process, not just bad luck. For more on how the law approaches these situations, see Reframe Legal — Medical Negligence.

When CGM-related care failures may amount to medical negligence

Medical negligence — in plain terms, care that falls below the standard a competent clinician would have provided, causing harm — can arise in CGM management in several specific ways.

If a clinician prescribed a Dexcom G6 or G7 and never explained that certain medications interfere with readings, and the patient then made an insulin decision based on a falsely elevated reading and suffered a serious hypoglycaemic episode, that failure of education may be legally significant.

If a diabetes educator or endocrinologist reviewed CGM reports at multiple appointments and saw clear evidence of nocturnal hypoglycaemia — time below range, low glucose events between 2am and 5am — and made no change to the treatment plan, that inaction may fall below the standard expected of a competent specialist.

The role of the NSW Civil Liability Act 2002

In New South Wales, the Civil Liability Act 2002 sets out the legal framework for assessing whether a clinician’s conduct was reasonable. The Act asks whether a competent clinician in the same position, with the same information, would have acted differently. It also requires that any harm suffered was a foreseeable result of the failure — not just an unfortunate coincidence.

A clinician who dismissed a patient’s concern about inaccurate CGM readings, told them to trust the device, and then adjusted their insulin upward based on falsely high readings — leading to a hospitalisation for severe hypoglycaemia — may have acted in a way that the Act would consider unreasonable.

When harm becomes long-term or permanent

A single hypoglycaemic episode can cause serious harm. Severe hypoglycaemia — where blood glucose drops to a level that impairs consciousness — can cause brain injury, cardiac arrhythmia, and in rare cases, death. Even episodes that do not reach that severity can cause falls, fractures, and car accidents.

Repeated hypoglycaemia, particularly when it goes unaddressed over months or years, causes a condition called hypoglycaemia unawareness. The body stops producing the warning symptoms — shakiness, sweating, hunger — that normally alert a person to a falling glucose level. Once hypoglycaemia unawareness develops, every future low becomes more dangerous because the person no longer feels it coming.

Psychological and financial consequences

Living with diabetes is already demanding. A CGM-related harm event — particularly a hospitalisation or a serious low — can cause significant anxiety about glucose management. Some people develop a fear of hypoglycaemia that leads them to run their glucose levels deliberately high, which carries its own long-term risks including kidney disease, nerve damage, and vision loss.

Financial consequences include the cost of hospitalisation, specialist review, additional monitoring equipment, and time away from work. For people in physically demanding jobs, a serious hypoglycaemic episode can end a career. Carers who provide support after a harm event also bear real costs that the law recognises.

What compensation can cover in CGM-related care cases

In New South Wales, compensation in a medical negligence case can cover several categories of loss. General damages cover pain, suffering, and loss of enjoyment of life. Special damages cover out-of-pocket expenses including medical costs, rehabilitation, and equipment. Lost income — both past and future — is also recoverable where harm has affected a person’s ability to work.

In CGM-related cases, compensation may also cover the cost of additional diabetes management support, psychological treatment for anxiety related to the harm event, and the cost of care provided by family members.

Each case is assessed on its own facts. These figures are general ranges only. Time limits apply to legal claims in NSW — generally three years from the date the person knew, or ought reasonably to have known, that they had suffered harm as a result of a clinician’s failure.

Bringing it together — do the pieces fit?

If you have read this far, something in your experience likely resonated with what this article describes. The question now is whether the pieces of your situation fit together in a way that is worth examining more carefully.

Understanding how the pieces connect — what happened, what should have happened, and what the gap between those two things caused — is the foundation of any legal assessment. For a plain-English explanation of how that process works in NSW, see Reframe Legal — How Medical Negligence Claims Work in NSW.

You don’t need certainty to understand your position

Most people who have been harmed by a care failure do not feel certain about what happened. They feel confused. They wonder whether they are being unfair to a clinician who seemed to be trying. They second-guess their own memory of what they were told.

That uncertainty is normal. Legal clarity does not come from the patient being certain — it comes from examining the facts carefully, comparing them against what a competent clinician would have done, and forming a view based on evidence. You do not need to arrive at a lawyer’s office already knowing the answer.

If your situation involved a question about what you were told before starting CGM therapy — or what you were not told — the law around informed consent may also be relevant. Patients have a right to understand the limitations of any medical device prescribed to them. For more on that, see Reframe Legal — Informed Consent and Medical Negligence.

If you want to understand more about the regulatory framework that governs health practitioners in Australia, AHPRA — Australian Health Practitioner Regulation Agency maintains publicly accessible information about practitioner standards and the complaints process.

About the lawyer behind this article

Dr Rosemary Listing is a NSW lawyer with a PhD focused on medical negligence. Her academic and legal work examines how clinical systems fail patients — not just individual clinicians, but the processes and decisions that surround them.

Rosemary has worked on cases involving diabetes management failures, including situations where clinicians misinterpreted CGM data, failed to act on documented hypoglycaemia patterns, or provided inadequate education about device limitations. She understands both the clinical context and the legal framework that applies to these situations in NSW.

In her experience, the harm in CGM-related cases often comes not from the device itself, but from the gap between what the data showed and what the clinician did with it. A device that flags repeated overnight lows is only useful if someone acts on what it is showing.

People who approach Rosemary are not usually looking to blame anyone. Most want to understand what happened and whether the care they received was reasonable. Her role is to examine the facts carefully and give an honest assessment of whether the standard of care was met.

Rosemary practises in New South Wales. Her work is grounded in the view that patients who trusted a system deserve a clear explanation when that system let them down.

This article is general legal information only. It does not constitute legal advice. Each person’s circumstances are different. The law discussed applies to New South Wales, Australia. Time limits apply to legal claims.