10 Quick & Easy Steps to Interpret Sensor Glucose Data
Written by Carolien Koreneff, Credentialled Diabetes Educator
More and more people with diabetes are choosing to use flash glucose monitoring or continuous glucose monitoring (CGM) systems to manage their diabetes.1 However, if you’re like most health professionals, it can be a challenge to assist your patients in interpreting flash glucose monitoring and CGM systems data given the limited time a clinical consult offers. Luckily Credentialled Diabetes Educator, Carolien Koreneff simplifies the process in 10 quick and easy steps.
Currently only people with type 1 diabetes, who fulfil certain criteria, are eligible to access the sensors free of charge through the National Diabetes Services Scheme (NDSS). However many people with diabetes, including those with type 2 diabetes, find it a worthwhile investment to access these systems privately. After all, flash glucose monitoring and CGM systems capture up to 288 glucose data points in just one day. With many of the current systems on the market not requiring any finger pricks. Not even for calibration or insulin dose adjustments.
Step 1: Check Sensor Usage
The summary page provides information on the number of days the CGM has been worn and what percentage of time the CGM was active. For accurate and meaningful interpretation of the data it is important that adequate data, is available. Therefore, recommendations are, to aim for around 70% of data, collected over 14 days of sensor wear.2
Step 2: Glycaemic Variability
The Summary Page also provides information on the mean glucose, the glycaemic variability (GV), and the coefficient of variation, reported as %CV. It is generally recommended to aim for <36%CV, although some studies suggest that lower %CV targets (<33%) may provide additional protection against hypoglycaemia.1
Step 3: Standard Deviation
Standard Deviation (SD) is the most familiar GV measure for most healthcare professionals, it highly correlates with mean glucose and HbA1C. If the SD is less than the mean glucose divided by 3 (with mean glucose of 3.9-10.0 mmol/L), it is reasonable to assume a low GV and a stable glucose profile.2
Step 4: Time in Range
Time in Range (TIR) is another essential part of this report. To quantitate the amount of time a person is spending with their glucose levels in, above or below range, there are 5 categories. You can read this article to find out more about Time In Range.
Step 5: Basal-Bolus Division
When working with people with type 1 diabetes, it is recommended they have a relatively even distribution between the basal and the bolus insulin. As a result, most diabetes specialists recommend either a 50-50 or a 40-60 split between the basal and the bolus insulin in a 24-hour period.
Step 6: Identify Glucose Patterns
The Glossary page, in many systems referred to as the Ambulatory Glucose Profile page (or AGP report), allows you to quickly identify patterns through a single curve representing the average sensor glucose along with interquartile and interdecile ranges.3
Using this curve, you can easily assess the extent to which values are within the target range and any times of day that pose low or high patterns requiring immediate attention.
Now that you have some overview of what is going on, it is time to see if insulin dose adjustments are needed. In order to do this, it is recommended to:
Step 7: Attend to any hypoglycaemia
First look for any evidence of hypoglycaemia.3 If hypoglycaemia is identified, check if there are any patterns of hypoglycaemia. For example, hypoglycaemia at a particular time of the day, after physical activity or linked to menses.
Talk to the person with diabetes about these hypos, what they believe may have caused them or how they think they may be able to prevent these hypos in the future. Adjust insulin doses as needed to prevent further hypoglycaemia.
It is vital to deal with any hypoglycaemia first, before considering any other changes, as hypoglycaemia is an acute complication of diabetes.
Step 8: Fix the Fasting
Adjust the basal before making any changes to any of the bolus injections. But, before you can do this, you will need to exclude any potential nocturnal hypoglycaemia as a cause for rebound fasting hyperglycaemia.
Titrate the basal insulin to fasting and overnight glucose levels and avoid the temptation to “try and fix it all in one day”.
If you have suggested any changes in insulin treatment by now, it is a good idea to review these changes after about a week, before making any additional changes. This will allow you to assess what actually worked.
Step 9: Attend to any hyperglycaemia
Many people are terrified of having high blood glucose levels, due to the associated risk of developing diabetes related complications. If you have made any changes in the treatment as outlined in step 8, reassure your patient that a few weeks of higher levels do not significantly increase their risk of developing or worsening diabetes related complications. It is a good opportunity to reinforce the need for further follow up.
Step 10: Get insight into the person’s routine
When educating patients there are a variety of things to consider, such as:4
- Does the person avoid or override bolus calculator suggestions?
- Do they bolus before main meals? (Ideally bolus insulin is administered 10-15 minutes before the meal).
- Are they counting their carbohydrates accurately?
- Do they have clear clinical targets?
- Is the Insulin to Carbohydrate Ratio accurate?
- Is the Insulin Sensitivity Factor adequate?
Patient Education Resources
Consider providing the patient with a referral to see a credentialled diabetes educator (CDE), if you haven’t done so already. CDEs can assist you with any of the above and talk to the patient about other important topics of conversation, such as:
- Sick day management
- Travel and Diabetes
- Diabetes and driving
- Pregnancy planning
- To view fact sheets on these topics click here
You can find a local CDE through the “find a CDE” function on the home page of the Australian Diabetes Educators Association website.
- Battelino, T et al. “Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations from the International Consensus on Time in Range.” Diabetes care vol. 42,8 (2019): 1593-1603. https://doi.org/10.2337/dci19-0028
- Bergenstal RM. “Understanding Continuous Glucose Monitoring Data”. 2018 Aug. In: Role of Continuous Glucose Monitoring in Diabetes Treatment. Arlington (VA): American Diabetes Association; 2018 Aug. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538967/ doi: 10.2337/db20181-20
- Hammond, P. “Interpreting the ambulatory glucose profile.” British Journal of Diabetes, vol. 16 (2016), supplement 1 https://doi.org/10.15277/bjd.2016.072
- Judge, C. “Interpreting Continuous Glucose Monitoring (CGM) Data.” Australian Diabetes Educator (2020), volume 23, number 2. https://ade.adea.com.au/interpreting-continuous-glucose-monitoring-cgm-data/