Compositions and formulations comprising insulin or insulin analogues comprising a carboxy terminal portion (CTP) peptide comprising amino acids 112-188 to 142 of the beta subunit of human chorionic gonadotropin (hCGβ) or a partial variant thereof that includes at least one O-glycosylation site of the CTP peptide, wherein the CTP peptide of the CTP peptide-based insulin or insulin analogue is O-glycosylated are described. In particular embodiments, the O-glycosylated insulin analogues are produced in vivo and in further embodiments, the O-glycosylated CTP-based insulin analogues comprise predominantly mannotriose and mannotetrose O-glycans or predominantly mannose O-glycans.