Bio Break: Understanding Continuous Glucose Monitors
Continuous glucose monitors (CGMs) are revolutionizing how people track blood sugar levels in real time. But how do they work, and where exactly do they measure glucose? In this episode of Bio Break, Nick and Joris explore the science behind CGMs, explaining the difference between blood glucose monitoring and interstitial fluid measurement—and why CGMs don’t actually draw blood continuously.
Rather than inserting a sensor directly into a vein, CGMs use microneedles or tiny tubes that sit in the interstitial fluid, the liquid surrounding the body’s cells. Unlike blood, which flows within veins, interstitial fluid is more accessible for continuous monitoring. However, there’s a key tradeoff—glucose levels in interstitial fluid lag behind blood glucose levels by about 5-10 minutes. This means CGMs don’t provide an instant blood sugar reading but rather a near-real-time estimate.
Nick raises an important question: does this time lag matter for diabetes management or sports performance tracking? Joris explains that while this delay exists, CGMs still offer huge advantages over traditional blood testing, which often requires finger pricks or lab draws that provide only a single data point. The ability to continuously measure glucose, lactate, or other small molecules gives users a clearer picture of how their body responds to food, exercise, and lifestyle changes.
However, not everything can be measured using interstitial fluid. Large molecules like hormones, red blood cells, and protein-bound compounds don’t diffuse as easily into interstitial fluid, making them difficult to track with a CGM. But for small molecules such as glucose, lactate, histamine, and creatinine, interstitial fluid monitoring is a powerful tool for real-time insights into metabolism.
If you’ve ever wondered how CGMs work or why they don’t require direct blood sampling, this episode breaks down the technology in a simple, engaging way.
Understanding Continuous Glucose Monitors
Related Resources
Accelerated aging in medical devices is a testing method used to estimate how a product will perform over time by exposing it to elevated conditions, most often heat. In simple terms, it is a way to simulate months or years of aging in a much shorter timeframe.
In a recent article for MD+DI, StarFish Medical Software Manager Sean Daniel explores how remote medical devices reliability is becoming a defining challenge as devices move beyond traditional clinical environments into homes, workplaces, and public settings.
This medical vs wellness example shows how device classification can directly change functionality. Even when hardware is similar, what the device is allowed to do can be very different.
Modern medical devices are no longer confined to hospital settings. Wearable cardiac monitors, home respiratory systems, and remote patient monitoring devices now operate within broader digital health networks.