Some tests require a fasting sample but many don't. We will tell you everything you need to know about any special requirements before you take your test. If we don't advise you to fast, that is because it isn't necessary for the test you are taking.
If you are required to fast, it is best to fast overnight and take your test in the morning so that you don't have to go too long without eating. Please make sure that you are well-hydrated. You can drink plenty of water and clear, calorie-free fluids like black tea and coffee. Just make sure you leave out the milk and sugar.