If LO appears on the reader, the user's result is lower than 40 mg/dL. If HI appears on the FreeStyle Libre 2 reader, the user's result is higher than 400 mg/dL. The user can touch the message button for more information. Check your blood glucose on your finger with a test strip. If you get a second LO or HI result after doing a blood glucose test, contact your health care professional immediately.