Interstitial Glucose
Also known as: Tissue Glucose, CGM Reading
Glucose concentration in the fluid between cells — what CGM sensors actually measure, which lags blood glucose by 5–10 minutes.
Continuous glucose monitors do not directly measure glucose in blood. Instead, they measure glucose in interstitial fluid — the fluid that surrounds cells in tissue. This fluid exchanges glucose with capillary blood through diffusion, but there is a physiological lag of approximately 5–10 minutes.
This lag is clinically relevant when glucose is changing rapidly. During a fast drop in blood glucose, CGM may still show a 'safe' reading when fingerstick blood glucose is already at hypoglycemic levels. This is why CGM trend arrows matter — a rapidly falling arrow warrants action before the number hits the alert threshold.
Most modern CGMs apply algorithmic calibration to minimize this lag effect and provide readings that closely track blood glucose during steady-state conditions. FDA-cleared CGMs must meet accuracy standards even accounting for this physiological lag.
Frequently asked
What is Interstitial Glucose?
Glucose concentration in the fluid between cells — what CGM sensors actually measure, which lags blood glucose by 5–10 minutes. Continuous glucose monitors do not directly measure glucose in blood. Instead, they measure glucose in interstitial fluid — the fluid that surrounds cells in tissue. This fluid exchanges glucose with capillary blood through diffusion, but there is a physiological lag of approximately 5–10 minutes.
How does Interstitial Glucose relate to Medicare coverage?
Medicare Part B covers most durable medical equipment related to Interstitial Glucose. Contact us to verify your specific coverage for related diabetic supplies.
Where can I get diabetic supplies related to Interstitial Glucose in Phoenix?
We deliver Medicare-covered diabetic supplies throughout the Phoenix metro area. Call us or complete the form above to verify your coverage.