Background: Dexamethasone improves COVID-outcomes. Detailed glycemic profile for patients receiving dexamethasone for COVID-is lacking. Methods: Our hospital recommends routine blood glucose monitoring for patients with COVID-receiving dexamethasone 6mg daily. Subjects without prior history of diabetes admitted in a non-critical care setting over a 1-month period were identified and evaluated. The primary outcome was hyperglycemia post-dexamethasone, defined as glucose ≥10mmol/L. Results: Of 277 subjects (52% male, age 52±18 yrs, weight 90±26 kg, 7% with newly diagnosed diabetes [HbA1c ≥6.5%]) , hyperglycemia post-dexamethasone occurred in 51%, with peak glucose 12.4±2.3 (mean 2.2 tests/day) . Glucose excursions peaked 7-9 hours post-dexamethasone (figure) . Hyperglycemic subjects were older (58±17 vs. 45±7 yrs, p<0.001) , had higher HbA1c (6.1±1.0 vs. 5.6±0.9%, p<0.001) , higher initial venous glucose (6.7±1.7 vs. 6.0±1.5mmol/L, p<0.001) , lower initial eGFR (80±18 vs. 84±15mL/min/m2, p=0.02) , higher initial CRP (969±640 vs. 791±558nmol/L, p=0.01) and greater mortality (7.7 vs. 1.5%, p=0.01) . Age, HbA1c and CRP were independent predictors of hyperglycemia. Conclusions: Dexamethasone led to hyperglycemia in half of patients without prior diabetes admitted with COVID-19, with peak occurring 7-9 hours after dexamethasone. Older age, higher HbA1c and initial CRP predicted development of hyperglycemia. Disclosure Y.J.Rhou: None. A.Hor: None. M.Wang: None. Y.Wu: None. D.R.Chipps: None. N.Cheung: None.