A Case of Factitious Hyperglycemia in a Patient on Intravenous Ascorbic Acid

Presentation Number: SUN-105
Date of Presentation: March 18, 2018, 2018

Eliza Sharma, MD, Christine Resta, MD, Patricia Park, MD.
Maimonides Medical Ctr, Brooklyn, NY, USA.

Abstract

INTRODUCTION
Finger stick blood glucose (FSBG) meters are widely used to measure blood glucose levels in outpatient and inpatient settings; however, various factors can affect accuracy of glucose readings from these meters. Here we present a case of marked interference with FSBG readings due to intravenous ascorbic acid.
CLINICAL CASE
An 81-year-old female underwent CABG and replacement of mitral valve, with postoperative course complicated by dehiscence of sternal wound requiring wound VAC, sacral decubitus ulcer, multiple episodes of sepsis, and respiratory failure. Her past medical history was significant for pre-diabetes and end stage renal disease on hemodialysis. The patient’s HbA1C at presentation was 6%, and her blood glucose was well-controlled during the first 45 days of admission with only 2 units total of sliding scale insulin required. She was started on IV ascorbic acid 10000 mg q 2 days to aid in sternal wound healing. Soon afterward, the patient had multiple high FSBG levels over 200 mg/dL, and she was treated with a total of 9 units of insulin in 24 hours. The FSBG levels remained high over the next few days with readings above 250 mg/dL. The patient was started on daily glargine insulin 10 units, which was increased to 25 units over the next few days. Of note, blood glucose in the metabolic panel (BGMP) ranged from 72-146 mg/dL, and comparison of simultaneous FSBG and BGMP revealed a marked discrepancy >100 mg/dL between readings. Given suspicion for intravenous ascorbic acid causing falsely high FSBG readings in this individual without previous insulin requirements, it was discontinued. FSBG
values decreased to normal. Fortunately, the patient did not have significant hypoglycemia while receiving unnecessary insulin treatment.
CONCLUSION
High dose ascorbic acid is a nutraceutical used mainly by alternative medicine practitioners for various indications. Physicians should be aware of the potential for high dose IV ascorbic acid to cause erroneously high readings on meters that use GDH-NAD reaction to measure glucose. The error arises when the meter reads ascorbic acid as glucose, as the two molecules have similar molecular weights. Spurious glucose elevation can also occur with glucose oxidase and GDH-FAD meters due to oxidation of ascorbic acid with generation of electrical current measured as glucose. Most laboratories measure venous glucose by the hexokinase method, which is not affected by ascorbic acid. In our patient, falsely high FSBG led to potentially harmful interventions. Physicians must understand the limitations of glucometer accuracy.
REFERENCE
Vasudevan S, Hirsch I. Interference of Intravenous Vitamin C With Blood Glucose testing. Diabetes Care 2014; 37;e93-94

Disclosures

 E. Sharma: None. C. Resta: None. P. Park: None.