The answer you expect to receive is directly proportional to the amount of information you provide us, we have no idea what your 3 word post is asking. If it's related to diabetes please clearly state what it is; if it was something a doctor told you, why he/she said it, something you read, and so on. For a non-diabetes definition of 'halo' go buy a dictionary or search online for one. Good luck -
other than angels and around the sun or moon ... no idea