Inclusion criteria:  Type 2 diabetes with duration > 6 months and age over 20; sufficient manual dexterity and visual acuity; willingness to wear two CGM devices and perform BG tests for 7 days.  Exclusion criteria:  untreated proliferative retinopathy; untreated mental illness that precludes study adherence untreated cardiovascular disorder such as unstable angina, severe heart failure, infectious diseases such untreated hepatitis, HIV, or active Covid-19; other severe body system disease.