The author utilizes quantitative analysis results based on diabetes control for two periods: the pre-COVID-19 period, from 5/5/2018 to 1/18/2020, and the COVID-19 period, from 1/19/2020 to 8/24/2020, within a duration of 2.3 years. Special attention has been placed on his specific lifestyle management during the COVID-19 quarantine period from 1/19/2020 to 8/24/2020. The COVID-19 period has a lower average Finger PPG (-6 mg/dL) along with a lower sensor PPG (-12 mg/dL). By comparing these two periods, the two glucose waveforms are similar in shape (with high correlation coefficient) and the differences between these two curves at each time instant are quite close to each other (about 12 mg/dL glucose difference). As a result, during this period, the author achieved 0.3% to 0.4% lower HbA1C value. COVID-19 is more than 100x worse compared to the fatal respiratory illness known as severe acute respiratory syndrome or SARS that occurred in 2003, in regard to its spreading speed, fatality number, and emotional impact on the world population. People belonging to the “vulnerable” groups, such as the elderly with existing chronic diseases and history of complications require special consideration to their health conditions and lifestyle management during the COVID-19 period. However, during this period, the author collected better results with his diabetes control in terms of both PPG and HbA1C values. The knowledge and experience he acquired in the past 10 years of medical research and his developed mathematical metabolism index model along with four diabetes prediction tools assisted him in many ways. As a result, he achieved a reduction of -6 mg/dL for finger PPG, -12 mg/dL for sensor PPG, -13 mg/dL for K-line PPG, and -0.3% to -0.4% for HbA1C. In fact, he turned the COVID-19 crisis into his health advantage!