Inclusion Criteria:  18 years of age or older Have diabetes (type 1 diabetes mellitus, type 2 diabetes mellitus, cystic fibrosis related diabetes mellitus) Hemoglobin A1c greater than or equal to 8.0% or history of hypoglycemia unawareness Able and willing to sign informed consent form Have a valid telephone number Willing to purchase FreeStyle Libre 2 CGM sensors out of pocket after discharge from hospital (when insurance coverage isn't available)  Exclusion Criteria:  Unable to sign informed consent form Have altered mental status Unable to manage diabetes independently at home Have utilized CGM in the past Pregnancy New steroid-induced hyperglycemia Unwilling to participate in the study Have kidney disease requiring hemodialysis Taking high doses of vitamin C daily (greater than 500 mg every day)