Prepare for your Fitness Blood Test by following these instructions. Please take your sample before 10am. Take this test when any symptoms of short-term illness have settled. Avoid heavy exercise for 48 hours beforehand. Avoid fatty foods for eight hours before your test, you do not need to fast. Avoid taking your sample from a finger used to apply hormone gels/pessaries in the past 4 weeks. Use gloves to apply these. 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.