Suggest Dosage Of Glibenclamide Diabetic Medicine

Hi. My husbands just discovered that he is diabetic and was given Glibenclamide-5mg by his doctor. He was advised to take half of it every time before meal. My question is, is half a tablet effective and as he is new to this routine, he tend to forget to take the tablet before meal. Can he still take it after his meal then? Thanks.