A Convenient Method for Measuring Blood Ascorbate Concentrations in Patients Receiving High-Dose Intravenous Ascorbate

Objective: A simple method of using fingerstick blood glucose (FSBG) monitors to estimate blood ascorbate values after high-dose intravenous (IV) ascorbate infusion is evaluated as a substitution for high-performance liquid chromatography (HPLC) measurement. Methods: In 33 participants, readings from FSBG monitors were taken before and after IV ascorbate infusions at various time points, with the postinfusion FSBG readings subtracted from the baseline glucose readings. The results of the subtractions (AA(FSBG)) were correlated with ascorbate concentrations detected by HPLC (AA(HPLC)). Results: A linear regression was found between ascorbate concentrations detected by the fingerstick method (AA(FSBG)) and by HPLC (AA(HPLC)). The linear correlations were identical in healthy subjects, diabetic subjects, and cancer patients. Analysis of variance obtained an AA(FSBG)/AA(HPLC) ratio of 0.90, with a 90% confidence interval of (0.69, 1.20). The corrections of AA(FSBG) improved similarity to AA(HPLC) but did not significantly differ from the uncorrected values. Conclusion: The FSBG method can be used as an approximate estimation of high blood ascorbate concentration after IV ascorbate (>50mg/dL, or 2.8mM) without correction. However, this measurement is not accurate in detecting lower or baseline blood ascorbate. It is also important to highlight that in regard to glucose monitoring, FSBG readings will be erroneously elevated following IV ascorbate use and insulin should not be administered to patients based on these readings.