Iron Deficiency in a 76-Year-Old Man: 'Can't I Just Take Pills?'

The labs confirm iron deficiency, not anemia of chronic disease. Ferritin 14 ng/mL with transferrin saturation 9% and microcytosis is diagnostic; inflammation would raise ferritin, not lower it. The thrombocytosis is reactive and does not require its own workup -- it should normalize as iron is replaced.

Differential, in priority order:

1. Colorectal cancer. Iron deficiency in an older man is a GI malignancy until proven otherwise. A normal colonoscopy 9 years ago does not exclude it -- that interval far exceeds any surveillance standard for a normal exam, and right-sided lesions bleed occultly and produce no melena.
2. Upper GI source: gastric cancer, peptic ulcer, erosive esophagitis, Cameron lesions, atrophic gastritis or H. pylori-related blood loss. A negative colonoscopy alone is an incomplete workup.
3. Celiac disease. Can present at any age with iron deficiency and no diarrhea.
4. Less likely: nutritional deficiency, urinary blood loss, malabsorption from PPI therapy alone.

Why aspirin plus a PPI does not close the case: aspirin may cause occult blood loss, and PPIs reduce iron absorption, so both are contributors. But a plausible partial explanation is exactly how a colorectal cancer gets diagnosed a year late. He also has unexplained weight loss and looser stools -- features that point at a structural lesion rather than drug effect.

Order bidirectional endoscopy -- both EGD and colonoscopy -- not one or the other. In iron deficiency anemia in an older adult, examining only the colon misses upper tract lesions; examining only the upper tract misses the most important diagnosis.

Add:

• Celiac serology (tissue transglutaminase IgA with a total IgA level, since IgA deficiency would make a negative tTG falsely reassuring).
• CMP, and H. pylori testing.
• B12 and folate, since mixed deficiencies are common and would blunt the MCV response.

Do not substitute CT colonography, stool DNA, or a repeat FIT for endoscopy. Those tools are for average-risk screening; in symptomatic iron deficiency anemia they have inadequate sensitivity and, critically, they do not obtain tissue.

What I tell him: iron will make his blood count look better without touching the cause, and that improvement can hide ongoing bleeding -- which is the reason the scope is the point of the visit, not an optional extra. I also validate the underlying concern: he is worried about the bowel prep and about what will be found. Explain that the preparation can be modified, that the endoscopy is generally well tolerated with sedation, and that finding nothing is itself valuable information. Start iron today rather than making replacement contingent on the procedure -- the workup and the treatment are not in competition.

Alternate-day oral dosing, not daily. Daily dosing raises hepcidin for roughly 24 hours and paradoxically reduces fractional absorption; ferrous sulfate 325 mg (or equivalent 60-65 mg elemental iron) every other day on an empty stomach absorbs better than the same dose daily. If GI intolerance occurs, every-other-day dosing also helps adherence.

Modify for his medications: omeprazole reduces absorption. Options are to separate doses from the PPI as much as possible (limited benefit), reduce acid suppression if his reflux allows, or move to IV iron. In a 76-year-old with a positive FIT and unexplained weight loss who may have ongoing blood loss, IV iron (e.g., ferric carboxymaltose) is a legitimate first choice -- it bypasses absorption entirely and repletes faster.

Objective response markers:

• Reticulocyte count rise within 7-10 days.
• Hemoglobin rise of roughly 1 g/dL every 2-3 weeks; recheck CBC at about 4 weeks.
• Continue therapy roughly 3 months after hemoglobin normalizes to refill stores, then recheck ferritin and transferrin saturation.

The most important follow-up is not hematologic: if the endoscopy is negative and the anemia does not correct, or corrects and then recurs, that is a signal to look further (small bowel evaluation) rather than simply to keep prescribing iron.