 A capsule containing radiolabelled 75SeHCAT (with 370 kBq of Selenium-75 and less than 0.1 mg SeHCAT) is taken orally with water, to ensure passage of the capsule into the gastrointestinal tract.The physical half life of 75Se is approximately 118 days; activity is adjusted to a standard reference date.Patients may be given instructions to fast prior to capsule administration; there is significant variation in clinical practice in this regard.