FAQs

Answers to the most frequently asked questions from primary care clinicians regarding CGM.

From the 2021 AACE Clinical Practice Guideline:  

  • CGM is strongly recommended for all persons with diabetes treated with intensive insulin therapy, defined as 3 or more injections of insulin per day or the use of an insulin pump
  • CGM is recommended for all individuals with problematic hypoglycemia (frequent/severe hypoglycemia, nocturnal hypoglycemia, hypoglycemia unawareness)
  • CGM is recommended for children/adolescents with T1D
  • CGM is recommended for pregnant women with T1D and T2D treated with intensive insulin therapy
  • CGM is recommended for women with gestational diabetes mellitus (GDM) on insulin therapy
  • CGM may be recommended for women with GDM who are not on insulin therapy
  • CGM may be recommended for individuals with T2D who are treated with less intensive insulin therapy

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

According to the Association of Diabetes Care & Education Specialists,

“CGM is appropriate for all people receiving diabetes medication. It allows people with diabetes to play an active role in their diabetes care, which is so important in shared decision-making. CGM teaches people how their medications, specific foods, exercise, stress, work, and other factors influence their daily glucose results. CGM can help motivate people to make positive lifestyle changes. Identifying the individual’s needs will ensure that appropriate expectations for the team are met.”

Reference: Association of Diabetes Care & Education Specialists. Continuous Glucose Monitoring: FAQs for Diabetes Care and Education Specialists. https://www.diabeteseducator.org/docs/default-source/practice/educator-tools/SMBG/cgm_practicepearls.pdf?sfvrsn=a0ce9b58_2

From the 2021 AACE Clinical Practice Guideline:

Real-time continuous glucose monitoring (rtCGM) should be recommended over intermittently scanned continuous glucose monitoring (isCGM) to persons with diabetes with problematic hypoglycemia (frequent/severe hypoglycemia, nocturnal hypoglycemia, and hypoglycemia unawareness) who require predictive alarms/alerts. However, the lifestyle of persons with diabetes and other factors should also be considered.

isCGM should be considered for persons with diabetes who meet 1 or more of the following criteria:

  • Newly diagnosed with T2D
  • Treated with nonhypoglycemic therapies
  • Motivated to scan device several times per day
  • At low risk for hypoglycemia, but desire more data than SMBG provides

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

From the 2021 AACE Clinical Practice Guideline:

Diagnostic/professional CGM should be used in the management of persons with diabetes who meet 1 or more of the following criteria:

  • Newly diagnosed with diabetes mellitus
  • Not using CGM
  • May have problematic hypoglycemia, but no access to personal CGM
  • Persons with T2D treated with non-insulin therapies who would benefit from episodic use of CGM as an educational tool
  • Persons who would like to learn more about CGM before committing to daily use

Importantly, in those using “masked” or “blinded” diagnostic/professional CGM, they must have and continue using adjunctive SMBG to assist in daily diabetes self-care.

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

From the 2021 AACE Clinical Practice Guideline:

Intermittent/occasional CGM may be recommended for the management of persons with diabetes who are reluctant or unable to commit to routine CGM use.

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

What are the priority metrics for clinical decision-making regarding the use of diabetes technology?

From the 2021 AACE Clinical Practice Guideline:

Established clinical targets should be used to individualize glycemic targets and adjust therapy based on each individual’s overall health status, concomitant medical condition (eg, pregnancy, frailty), and risk for hypoglycemia: 

All Persons With Diabetes

  • Number of days of active CGM use: 14 days preferred
  • Percentage of data available from active CGM use: > 70% of data from 14 days
  • Mean glucose: Individualized to targets
  • Glucose management indicator (GMI): Individualized to targets
  • Glycemic variability, percent coefficient of variation (%CV [coefficient of variation]): ≤ 36%

Type 1 Diabetes (T1D)/Type 2 Diabetes (T2D)

  • Percentage of time in range (%TIR) 70 to 180 mg/dL: > 70%
  • Percentage of time below range (%TBR) < 70 mg/dL: < 4%
  • %TBR < 54 mg/dL: < 1%
  • Percentage of time above range (%TAR) > 180 mg/dL: < 25%
  • %TAR > 250 mg/dL: < 5%

Older/High Risk T1D/T2D

  • %TIR 70 to 180 mg/dL: > 50%
  • %TBR < 70 mg/dL: < 1%
  • %TBR < 54 mg/dL: ~0%
  • %TAR > 250 mg/dL: < 10%

Pregnancy: T1D

  • %TIR 63 to 140 mg/dL: > 70%
  • %TBR < 63 mg/dL: < 4%
  • %TBR < 54 mg/dL: < 1%
  • %TAR > 140 mg/dL: < 25%

Two metrics, %TIR and %TBR, should be used as a starting point for the assessment of quality of glycemic control and as the basis for therapy adjustment, with emphasis on reducing %TBR when the percentages of CGM values falling below 54 mg/dL or 70 mg/dL are close to or exceed targets.

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

From the 2021 AACE Clinical Practice Guideline:

The AGP may be utilized to assess glycemic status in persons with diabetes.

When using the AGP, a systematic approach to interpret CGM data is recommended:

  1. Review overall glycemic status (eg, GMI, average glucose)
  2. Check TBR, TIR, and TAR statistics, focusing on hypoglycemia (TBR) first. If the TBR statistics are above the cut-point for the clinical scenario (ie, for most withT1D > 4% < 70 mg/dL; > 1% < 54 mg/dL), the visit should focus on this issue. Otherwise, move on to the TIR and TAR statistics.
  3. Review the 24-hour glucose profile to identify the time(s) and magnitude(s) of the problem identified
  4. Review treatment regimen and adjust as needed

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

Glycated hemoglobin (A1C or HbA1c), which reflects average levels of blood glucose over the previous two to three months, is a widely used metric for both the diagnosis and management of diabetes. However, A1C does not provide a reflection of intra-day or inter-day glucose excursions. Glucose management indicator (GMI) is calculated from CGM-derived mean glucose over ~14 days for a given individual. This is a new term for estimating A1C. GMI (%) is calculated using the formula: 3.31 + 0.02392 x [mean glucose in mg/dL]. 

Reference: Bergenstal RM, et al. Glucose management indicator (GMI): a new term for estimating A1C from continuous glucose monitoring. Diabetes Care. 2018;41:2275-2280. https://pubmed.ncbi.nlm.nih.gov/30224348/

From the 2021 AACE Clinical Practice Guideline:

With the use of CGM, clinicians should make a reasonable effort to ascertain that a person with diabetes is not inadvertently ingesting a substance or medication that will cause the CGM to deliver false or misleading information. Furthermore, clinicians should make a reasonable effort to make persons with diabetes aware of the theoretical risk of radiation exposure to diabetes technologies.

Persons with diabetes who have a care provider, such as a spouse, adult child of a geriatric person with diabetes, or parent of a child with diabetes, who remotely monitors glucose data, should be cautioned that remote glucose monitoring is dependent upon server functionality and that data interruption can result. Back-up plans of having persons with diabetes revert to SMBG or methods to communicate CGM data to those who remotely follow will be needed until functionality can be restored.

Reference: Grunberger G, et al. American Association of Clinical Endocrinology Clinical Practice Guideline: The Use of Advanced Technology in the Management of Persons with Diabetes Mellitus. Endocrine Practice. 2021;27:505-537. https://pubmed.ncbi.nlm.nih.gov/34116789/

Manufacturers of CGM devices have many online videos and other resources for individuals considering CGM. Importantly, the diabetes health care team plays a key role in patient education, satisfaction, and proper use of CGM devices.

The Association of Diabetes Care & Education Specialists recommends the following:

  • After initial CGM sensor placement, people with diabetes should be advised to keep a detailed profile of meals, exercise, medication administration, alcohol consumption, and sleep. They should be given a follow-up appointment to review the data, and they should be advised to continue with any therapy changes until that follow-up.
  • At the follow-up visit, the team can work together to recognize hypoglycemia risk, evaluate patterns of low or high readings, uncover any obstacles to monitoring, and consider potential therapy changes
  • For personal-use CGM devices, trend arrows allow people to see the rate and direction of their glucose changes, allowing them to adjust the insulin dose as needed to prevent potentially dangerous glycemic events

Reference: Association of Diabetes Care & Education Specialists. Continuous Glucose Monitoring: FAQs for Diabetes Care and Education Specialists. https://www.diabeteseducator.org/docs/default-source/practice/educator-tools/SMBG/cgm_practicepearls.pdf?sfvrsn=a0ce9b58_2

Each CGM device is unique including the alarm features, and for some people these alarms/alerts may be stressful. Providers can help CGM users set the alarms and discuss the importance of having the alerts go off at important times, such as during hypoglycemia. CGM can provide a tremendous amount of information, but this may be overwhelming for new users of a CGM device. It may help new users to look at the device at key times only, such as before meals, before bedtime, and before activities like exercising or driving; and to use CGM to determine glycemic trends. Patients should be counseled to reach out to the care team with questions, concerns, or when feeling overwhelmed—be sure to provide email contacts and/or phone numbers for help that is available!

Reference: Association of Diabetes Care & Education Specialists. Continuous Glucose Monitoring: FAQs for Diabetes Care and Education Specialists. https://www.diabeteseducator.org/docs/default-source/practice/educator-tools/SMBG/cgm_practicepearls.pdf?sfvrsn=a0ce9b58_2

  • Adequate time needs to be scheduled for CGM review, particularly in the primary care setting 
  • Ensure a clear understanding with the patient that the focus of the visit is to review CGM data.
  • Individuals should be encouraged to use their CGM devices consistently for at least 14 days to see glucose patterns and trends. When possible, CGM data should be uploaded to an online portal.
  • When professional CGM has been used, download the data before the clinician joins the patient. This can provide the person with diabetes time to review key metrics and patterns, consider the implications of the results, and formulate questions prior to a discussion.

Reference: Association of Diabetes Care & Education Specialists. Continuous Glucose Monitoring: FAQs for Diabetes Care and Education Specialists. https://www.diabeteseducator.org/docs/default-source/practice/educator-tools/SMBG/cgm_practicepearls.pdf?sfvrsn=a0ce9b58_2

Through in-person demonstrations or with online videos, show the person with diabetes the size of different devices and the discreet places on the body where they can be worn. Many of the device companies include patient stories of their experiences with CGM, which may provide additional insight. In addition, starting with a professional CGM is a way for a person to get a feel for what it would be like to use CGM prior to making the commitment for a personal device.

Reference: Association of Diabetes Care & Education Specialists. Continuous Glucose Monitoring: FAQs for Diabetes Care and Education Specialists. https://www.diabeteseducator.org/docs/default-source/practice/educator-tools/SMBG/cgm_practicepearls.pdf?sfvrsn=a0ce9b58_2

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