The FreeStyle Libre 14 day system is accurate1 in the range between 40 to 500 mg/dL and only shows glucose values in this range. If "LO" appears on the reader, your reading is below 40 mg/dL; check your blood glucose again with a test strip. If "HI" appears in your reader, your reading is above 500 mg/dL; check your blood glucose again with a test strip. If a second "LO" or "HI" result appears, contact your health care professional immediately.
1 FreeStyle Libre 14 day User's Manual