Thank you all for your replies:
WishfullnHopefull: I have carefully examined and tried to improve my diet to consume more iron, including the resumption of eating meat (I was a vegetarian). Unfortunately, these changes alone have not been sufficient to eradicate the anemia.
Ihadcancer: I sent you a private message. I do have some other symptoms of colon cancer, like weight loss, nausea, and vomiting. My GI is looking into the nausea and vomiting. Had an endoscopy in March. They found nothing. Having a gastric emptying study on May 30 related to the nausea and vomiting. Fortunately, I have no family history of colon cancer.
Brick5711: Brick, what finally convinced you or your doctors to do a colonoscopy?
To all--I have scheduled an appointment with my GI next week strictly to discuss the undiagnosed anemia. If he doesn't suggest it, I will certainly inquire, if not insist, on a colonoscopy, if for no other reason than to put my mind at ease.