Chromium is a metallic element (atomic number: 24, atomic mass: 51.99), it is a mineral essential in the action of insulin and is present in very small quantities in many enzymes. Chromium is also present in many foods such as brewers' yeast, seeds, peanuts, wheat germ and skimmed milk. Chromium Cr-51 is an isotope of chromium that is observationally stable. When intravenously administered, it is used as a diagnostic radiopharmaceutical agent to determine the red blood cell volume or mass, study the red blood cell survival time and evaluate blood loss. Chromium 51 is also used for labeling platelets, and for the diagnosis of gastrointestinal bleeding.