Optimal Sampling Duration for Continuous Glucose Monitoring to Determine Long-Term Glycemic Control

Diabetes Technol Ther. 2018 Apr;20(4):314-316. doi: 10.1089/dia.2017.0455. Epub 2018 Mar 22.


Objective: To determine the minimum sample of continuous glucose monitoring (CGM) data needed to accurately reflect 3 months of glycemic control.

Research design and methods: Three months of CGM data were collected on 257 individuals (age 10-78 years) with type 1 diabetes in two studies (one using the Abbott FreeStyle Libre Pro™ and the other using the Dexcom™ G4). Correlations were calculated between the full 3 months and incremental sampling periods of CGM data.

Results: Correlation to the full 3 months of data improved with an increasing number of days of data collection, plateauing by about 14 days, with an R2 value of 0.84-0.86 for mean glucose, time at 70-180 mg/dL, and time >180 mg/dL, with lower values for time <70 mg/dL (0.76) and coefficient of variation (0.70).

Conclusions: Fourteen days of CGM data provide a good estimation of glucose metrics for a 3-month period.

Keywords: Continuous glucose monitoring; Data sampling; Type 1 diabetes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Blood Glucose / analysis*
  • Blood Glucose Self-Monitoring / methods*
  • Child
  • Diabetes Mellitus, Type 1 / blood*
  • Diabetes Mellitus, Type 1 / drug therapy
  • Female
  • Glycated Hemoglobin A / analysis
  • Humans
  • Hypoglycemic Agents / therapeutic use
  • Male
  • Middle Aged
  • Time Factors
  • Young Adult


  • Blood Glucose
  • Glycated Hemoglobin A
  • Hypoglycemic Agents