Glucose levels can be measured from the bloodstream or from the interstitial fluid (ISF), which surrounds the body’s cells. There is a 5- to 10-minute delay in ISF glucose response to changes in blood glucose,¹ which is unlikely to impact routine day-to-day treatment decisions. The average lag time of the FreeStyle Libre systems^ is about 2.1 minutes for children and about 2.4 minutes for adults.²

ISF glucose and BG measurements taken simultaneously won’t always match, and, in fact, are likely to be different.

1. Rebrin K, Sheppard NF Jr, Steil GM. Use of subcutaneous interstitial fluid glucose to estimate blood glucose: revisiting delay and Sensor offset. J Diabetes Sci Technol. 2010;4(5):1087-1098.
2. Alva S. et al, “Accuracy of a 14-Day Factory-Calibrated Continuous Glucose Monitoring System with
Advanced Algorithm in Pediatric and Adult Population With Diabetes. Journal of Diabetes Science
and Technology, (September 2020). http://doi.org/10.1177/1932296820958754.

^ FreeStyle Libre 2 and FreeStyle Libre 3 systems are part of the same family of products.