Prepare for your Advanced Diet and Lifestyle Blood Test by following these instructions. Please take your sample before 10am. Avoid heavy exercise for 48 hours beforehand. Avoid fatty foods for eight hours before your test, you do not need to fast. Hormonal contraception can affect this test, taking a break from this and using barrier contraception will give more accurate results. Corticosteroid medication can affect this test, ask your doctor whether to stop before testing. You should take this test before you take any medication or vitamin/mineral supplements. Do not take biotin supplements for two days before this test, discuss this with your doctor if it is prescribed. Do not take vitamin B12 for two weeks prior to this test. If your B12 is prescribed ask your doctor whether to stop.