High blood sugar levels post covid.

Hello respected sir/mam ! My father had symptoms of covid (dry cough, fever and malaise) for 5 days following which we decided to get HRCT done and he had corads 5, with CT severity 5 out of 25. He had Rapid antigen and RT PCR test negative the following day after hrct. However keeping in mind the co-morbidities (diabetes, hypertension) the doctors advised to get hospitalised. He was admitted for 5 days. And his treatment was iv remdesvir, iv Methylprednisolone, loparin, and other drugs for covid and diabetes. However now he is discharged its 3rd day but the RBS remains very high (400-550). We are concerned about the hyperglycemia. Currently he is taking Teneligliptin, metformin and Glimpride since 3 days. Yet the sugar levels aren't controlled. Please suggest what must be done next?