Interstitial Fluid: Definition and Overview

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Cross-section of cells -- Interstitial Fluid: Definition and Overview

What is interstitial fluid?

The fluid that surrounds the cells of multicellular animals. The advent of sensors that can measure glucose in the interstitial fluid has allowed companies to develop devices for continuous glucose monitoring. However, because interstitial glucose levels are not identical to blood glucose levels, continuous monitoring devices (CGMs) must be calibrated with a blood glucose reading from time to time. Additionally, people using a continuous device may find it helpful to occasionally check their blood glucose with a conventional meter to confirm interstitial measurements.

Interstitial fluid monitoring

A number of glucose monitoring systems are now on the market, including those manufactured by Abbott, Dexcom, and Medtronic. Each of these systems consists of a glucose sensor placed under the skin and replaced every 3–7 days and a receiver that stores interstitial glucose measurements. Continuous glucose monitoring can detect trends in glucose levels as well as alert the user of high and low glucose levels. These trends and readings are displayed on a screen on the receiver.

Can continuous monitoring improve blood glucose control? Studies suggest that it can. According to a review commissioned by the Agency for Healthcare Research and Quality and conducted by the Evidence-based Practice Center at Johns Hopkins University, real-time continuous glucose monitoring was superior to regular blood glucose monitoring in lowering HbA1c in nonpregnant individuals with Type 1 diabetes, particularly when the CGM system was used routinely, without affecting the risk of severe hypoglycemia. In addition, overall diabetes treatment satisfaction was higher in those who used a combination insulin pump—CGM system.

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