Metformin comes in different dosage forms, so the dosage, usage and the time of use is different. If you are using Metformin Hydrochloride Enteric Tablets, which are usually used before meals, this medication can be taken three times a day, so that is before three meals, or twice a day, which is before two meals in the morning and evening. If you are using metformin extended-release tablets, it is recommended to take them before dinner or with dinner. So, the dosage form of metformin is different, the dosage chosen and the time of use is also different.