Are there other things that cause anemia besides iron-deficiency?

Chronic diseases: Such as sickle cell, thalassemia, , GI bleed, cancer, inflammatory bowel disease, renal disease can also cause anemia. Prenicious anemia (due to autoimmune destruction of special stomach cells), folate (folic acid) and B12 deficiencies are other causes. Talk with your docotr if special testing is required to determine etiology of anemia and if colonoscopy is required.

Anemia: There are dozens of causes of anemia. Cancers, infections, vitamin deficiencies, nutrient deficiencies, prosthetic heart valves, liver disease, kidney disease, ..... The workup for an anemia should be handled by a competent physician.