You can take lactulose with or without food at any time that suits you. When taking lactulose twice a day, it’s typically best to have one dose in the morning and one in the evening, ideally 10-12 hours apart. If you’re regularly taking lactulose and forget to take a dose, do not take an extra dose to make up for a forgotten one. Aim to drink 6 to 8 glasses of water during the day while you're taking lactulose or your constipation may get worse.