Comprehensive Guide to CGM Use: Selection and Implementation

Traditional glucose monitoring with finger-stick testing offers only limited, point-in-time information. Continuous glucose monitoring (CGM), by contrast, provides dynamic insights into glycemic patterns over days and weeks. 

Over the past decade, CGM technology has advanced rapidly, moving from initial use primarily in type 1 diabetes to becoming increasingly adopted for broader populations, including some with type 2 diabetes.

Primary care providers, endocrinologists, diabetes educators, and multidisciplinary care teams are increasingly incorporating CGM into routine management, consistent with current diabetes care guidelines. 

This guide compiles best practices for device selection, prescribing, patient education, data interpretation, and reimbursement, supporting providers in integrating CGM into practice with greater confidence and precision.

Clinical justification and CGM indications

Before adopting CGM in practice, it’s important to clarify when and how the technology should be used.

Types of CGM: Personal vs. professional

Personal CGM systems are prescribed to patients for continuous, long-term use. They allow real-time access to glucose data and often feature alarms or remote sharing with care teams. 

Professional CGM systems, in contrast, are owned by clinics and applied to patients for short diagnostic periods. These may be blinded (the patient cannot see the data until it’s reviewed) or unblinded (the data is accessible in real-time).

Another distinction is between flash CGM and real-time CGM. Flash CGM requires the patient to scan the sensor with a reader or smartphone to see their glucose level, meaning data is only available when scanned. Real-time CGM, on the other hand, automatically sends continuous readings to a receiver or phone and can provide alerts when glucose is trending too high or too low.

Evidence-based indications for CGM use

CGM is recommended in guidelines for individuals with type 1 diabetes and for many with type 2 diabetes who use insulin.

More recent guideline updates and expert consensus statements describe expanded clinical scenarios where CGM may be beneficial, including:

• Gestational diabetes and pregnancy management
• Glucose monitoring during chronic steroid use
• Post-bariatric hypoglycemia
• Chronic kidney disease with variable glucose control
• Older adults or patients at risk of hypoglycemia unawareness

CGM is also helpful when HbA1C values don’t match Self-Monitoring of Blood Glucose (SMBG) or when unexplained hypoglycemia occurs. 

Use in these populations should be individualized based on clinical judgment and device labeling.

When to use professional CGM

Professional CGM is commonly used for short-term glucose assessment, such as clarifying patterns, evaluating response to therapy, or when access to personal CGM is limited. It provides providers with structured data that can inform adjustments in management.

Device selection and workflow integration

Successful CGM adoption requires matching the right device with the right patient, while ensuring workflows are practical for the clinic.

Device selection should take into account validated performance metrics (such as mean absolute relative difference, or MARD), along with patient preferences, usability, compatibility with existing devices, and cost or coverage considerations.

Prescribing CGM in electronic medical records (EMRs)

Electronic health records can streamline the prescribing of CGM devices by incorporating order sets, ICD-10 linkage, and automated documentation templates. Prior authorization is often required by payers, and standardized forms can help improve the approval rates.

Training the patient: Sensor use, data access, and expectations

Patient training should include:

• Correct sensor insertion and site selection
• Understanding potential artifacts such as compression lows or lag times
• Device syncing and interpreting trend arrows
• Managing alerts and expectations

Structured patient education programs reduce early discontinuation and improve adherence.

Addressing common patient barriers and troubleshooting

Skin irritation may occur at the sensor site and can sometimes be reduced by using barrier wipes, adhesive patches, or rotating insertion sites.

Certain medications have been reported to interfere with glucose readings on specific CGM models under defined conditions. For example, acetaminophen and hydroxyurea have been reported to affect glucose readings on some CGM models. Providers should check device labeling and discuss possible interactions with patients.

Alarm fatigue, connectivity issues, and cost concerns can affect continued use. Setting individualized alarm thresholds, providing troubleshooting support, and reviewing options such as financial assistance programs or HSA/FSA accounts may help reduce these barriers and improve patient experience.

Implementation options by practice setting

CGM workflows can differ depending on practice size and resources:

• Small practices may have medical assistants or nurses assist with sensor placement, while providers review and discuss data during follow-up visits.
• Group practices often include registered dietitians, diabetes educators, or pharmacists in reviewing reports and supporting patient education.
• Telehealth settings may use mailed CGM kits combined with remote data uploads, allowing results to be reviewed during virtual appointments.

Interpreting CGM data and clinical decision-making

The value of CGM lies not only in data collection but also in effective interpretation.

CGM metrics that matter

Key metrics include:

• Time in range (TIR): Percentage of time glucose is within target (commonly 70–180 mg/dL).
• Time below range (TBR): Percentage of time spent in hypoglycemia, with consensus targets generally below 4%.
• Time above range (TAR): Percent of time in hyperglycemia.
• Coefficient of variation (%CV): A measure of variability, ideally less than 36%.
• Glucose management indicator (GMI): Estimated A1C derived from average glucose.

Using ambulatory glucose profile (AGP) reports

AGP reports provide a standardized summary of approximately 14 days of CGM data, giving providers and patients a single-page overview of glucose patterns. These reports highlight recurring daily trends such as mealtime rises, overnight lows, and overall variability.

When reviewed alongside patient logs of meals, physical activity, medication timing, and sleep, AGP reports become more meaningful by connecting data points to real-life behaviors. This context helps guide conversations about possible adjustments in therapy, lifestyle, or monitoring routines.

Translating CGM data into therapeutic change

CGM patterns (such as nocturnal hypoglycemia, post-meal glucose rises, or high variability) can help inform discussions about possible adjustments in therapy or lifestyle when interpreted in the context of current diabetes care guidelines. 

Medication changes should follow evidence-based diabetes guidelines and individual clinical assessment; CGM data alone shouldn’t dictate therapy.

After any clinical changes are made, CGM data can be re-reviewed to assess impact and safety.

Frequently asked questions (FAQs)

Providers often have practical questions when incorporating CGM into patient care. Below are some of the most common considerations, along with answers.

When is blinded CGM preferred over real-time CGM?

Blinded CGM is useful when objective data is needed without patient behavior changes influencing results, such as diagnostic assessments or medication trials.

How frequently should CGM data be reviewed in outpatient care?

Many professional guidelines suggest reviewing CGM data every 2–4 weeks for insulin-treated patients, with less frequent review appropriate for stable individuals.

Can CGM replace all fingerstick monitoring?

In many cases, CGM significantly reduces the need for fingersticks, but confirmatory tests may still be required during calibration, rapid glucose changes, or suspected device errors.

How do I handle CGM device signal loss or alarm errors in patients?

Educate patients to troubleshoot smartphone pairing, minimize interference, and report persistent issues to device support lines.

Key takeaways

• Continuous glucose monitoring provides a more complete picture of glycemic control than fingerstick testing and isincreasingly recommended for individuals with type 1 diabetes and many insulin-treated patients with type 2 diabetes.
• Device selection should consider accuracy, usability, integration, and cost, with options available for both long-term personal use and short-term professional monitoring.
• Patient education and support are critical to ensure proper sensor placement, reduce barriers like skin irritation or alarm fatigue, and improve adherence.
• CGM metrics such as time in range, variability, and ambulatory glucose profiles help guide evidence-based therapeutic decisions.
• Practices can implement CGM using different operational models, ranging from small in-office setups to virtual care platforms, with sustainability supported by improved outcomes and quality metrics.

Disclaimer:

This article is intended for educational purposes only and should not replace individualized clinical judgment. Healthcare providers should verify device indications, payer requirements, and regulatory updates before integrating CGM into patient care.