Medicine The cardinal rule is that appearance of iron deficiency in an adult male is most often due to …… until proven otherwise: A Nutritional deficiency B Gastrointestinal blood loss C Renal disease D Malabsorption of iron due to worm infestation 💡 Explanation The cardinal rule is that appearance of iron deficiency in an adult male is most often due to ...... until proven otherwise: ✓ Correct Answer: B. Gastrointestinal blood loss