Introduction: CGM and carbohydrate counting (CC) have been proven to improve glucose control in type 1 and 2 diabetic patients. Those who continuously use CGM in diabetes management review the data frequently, make changes based on that data, and improve insulin related glucose control. Current CGM data summaries are considered useful to both patients and providers who adjust therapy to reduce glucose (G) variability and hypoglycemia with resulting improvements in A1c. The following describes the immediate use of CGM data for a pharmacokinetic analysis of meal related interstitial fluid glucose changes determined by the amount and timing of insulin administration.
Method: It requires the use of industry developed mobile phone software (LibreLinkUp) to immediately and quantitatively evaluate the meal related glucose excursion. A specific meal related glucose/insulin ratio results which confirms (and can replace) carbohydrate counting when carb counting is difficult or impossible to assess. Interstitial fluid glucose is evaluated from the time of pre-meal insulin injection to the return to baseline. IFG is adjusted to plasma glucose values using an adjusted Volume of Distribution (Vd) based on Kg body weight and hematocrit. The glucose concentration peak is deconvoluted and the lowest post meal baseline change is subtracted. The difference is multiplied by the adjusted volume of distribution to obtain an estimate of the ingested carbohydrate presenting as interstitial fluid glucose.
Results: Examples of identical meals and timed insulin dosing are evaluated and compared. Reference: breakfast bagel 56 g CHO. Variables: Vd=157 dL; Peak Post Meal G = 128 mg/dL; Calculation: 128*e*157 = 54,627 mg rounded to 55 g. I = 16 unit. CHO/I ratio =3.4 g/unit. Same breakfast another day: Calculated: 53 g; third breakfast: 54 g.
Conclusion: Meal related CC compares well with the calculated ISF glucose appearance using real-time CGM data.
J.S. Melish: None.
