Herbal Medicine Interference with Continuous Glucose Monitoring System in Diabetes Management: A Case Report

Continuous glucose monitoring (CGM) systems have transformed diabetes management through improved glycemic control, leading to decreased adverse events such as cardiovascular disease, neuropathy, retinopathy and nephropathy. However, there are documented, known interactions with several commonly used substances that are available over the counter, such as acetaminophen, aspirin, and Vitamin C, that affect the accuracy of CGM glucose readings. The Food and Drug Administration (FDA) released an alert November 2025 regarding incorrect low glucose readings associated with the Freestyle Libre CGM system after the manufacturer received 736 severe adverse events and seven deaths related to this issue. The FDA warns that incorrect low glucose readings may lead to inappropriate treatment decisions, including patient self-management where the patient may skip or delay insulin administration, leading to serious complications including death.This case report describes herbal supplement usage, purchased over the counter, causing interference with Freestyle Libre CGM system, where the CGM system provided incorrect, low glucose readings that masked hyperglycemia present, confirmed through fingerstick and hemoglobin A1c (HA1c) monitoring. This is the first case report to detail the interaction between a CGM system and herbal supplements, as there are no other case reports available through literature review. This case report highlights that herbal supplements may exhibit pharmacologic activity and a complete, comprehensive medication review including vitamins and homeopathic supplements are necessary to protect the public from avoidable, unintended harm. Additionally, further research regarding herbal supplements and public use are warranted with respect to adverse drug events and patient outcomes including emergency department utilization, hospitalization, and mortality.