How to manage a patient with low serum iron and normal ferritin, with a history of iron deficiency, diabetes, hypertension, and constipation?

Management of Low Serum Iron with Normal Ferritin in a Patient with Prior Iron Deficiency

This patient requires gastrointestinal investigation to exclude occult bleeding sources, particularly given the history of diabetes, age over 60, and previous iron deficiency, despite the normal hemoglobin and ferritin levels. 1

Interpretation of Iron Studies

Your patient presents with a complex iron picture that warrants careful interpretation:

• Serum iron 8 (low) with transferrin saturation 11.2% (markedly reduced) but ferritin 59 (normal range)
• MCV 79 and MCH 25 indicate microcytosis and hypochromia, consistent with iron deficiency 1
• This pattern suggests either early/evolving iron deficiency or functional iron deficiency where inflammation may be masking true iron depletion 1

Key diagnostic principle: Ferritin is an acute phase reactant and can be falsely normal or elevated in the presence of inflammation, infection, or chronic disease, even when true iron deficiency exists 1. A ferritin of 59 does not exclude iron deficiency in this context, particularly with a transferrin saturation <16% 1.

Why This Patient Needs Investigation

All patients over 60 years with confirmed or suspected iron deficiency require gastrointestinal evaluation to exclude malignancy and other serious pathology 1. The British Society of Gastroenterology guidelines are explicit that investigation should be considered at any level of anaemia in the presence of iron deficiency, though your patient is not yet anemic 1.

Critical factors mandating investigation in this case:

• Age 60 years - increased risk of gastrointestinal malignancy 1
• Previous iron deficiency ~5 years ago - suggests ongoing or recurrent blood loss 1
• Microcytic indices (MCV 79, MCH 25) with low transferrin saturation - consistent with iron-deficient erythropoiesis 1
• Male gender - in men, iron deficiency almost always indicates gastrointestinal blood loss until proven otherwise 2, 3, 4

Recommended Gastrointestinal Evaluation

Upper and lower gastrointestinal endoscopy should both be performed 1:

• Upper endoscopy with duodenal biopsies to screen for celiac disease (2-3% prevalence in iron deficiency anemia patients) and to identify gastric/duodenal pathology 1
• Colonoscopy to exclude colonic cancer, polyps, angiodysplasia, and inflammatory bowel disease 1
• Dual pathology occurs in 10% of cases, so both upper and lower tract must be examined even if one reveals a lesion 1

Common pitfall: Do not assume NSAID use or diabetes medications explain the iron deficiency without endoscopic confirmation. While this patient is not on NSAIDs currently, investigation remains mandatory 1.

Immediate Management Steps

1. Medication Review

• Stop lactulose if possible - may worsen iron absorption and is contributing to constipation issues 1
• Ensure metformin is not causing malabsorption (though less likely with these iron studies) 1

2. Dietary Counseling

• Increase dietary iron intake from haem sources (red meat, seafood) which have superior bioavailability 1
• Co-ingest vitamin C with meals to enhance non-haem iron absorption 1
• Avoid tea and coffee around mealtimes as they impair iron absorption 1

3. Iron Supplementation Trial

Initiate oral iron therapy while awaiting endoscopy 1:

• Ferrous sulfate 200mg three times daily (or ferrous gluconate/fumarate as alternatives) 1
• A good response to iron therapy (hemoglobin rise ≥10 g/L within 2 weeks in anemic patients, or improvement in iron indices in non-anemic patients) is highly suggestive of true iron deficiency even with equivocal ferritin 1
• Continue iron for 3 months after correction to replenish stores 1

Important caveat: Gastrointestinal side effects including constipation and nausea are common with oral iron 1. This may exacerbate this patient's existing constipation issues. Consider starting with once-daily dosing and titrating up, or using alternate-day dosing which may improve tolerability.

Monitoring Strategy

• Recheck complete blood count and iron studies in 3-4 weeks to assess response to iron therapy 1
• Expected hemoglobin rise of 2 g/dL after 3-4 weeks if anemia develops 1
• Failure to respond suggests continued blood loss, malabsorption, non-compliance, or incorrect diagnosis 1, 3

Long-term Follow-up

Once iron indices normalize:

• Monitor hemoglobin and MCV every 3 months for 1 year, then annually 1
• Further investigation is warranted if hemoglobin/MCV cannot be maintained with supplementation 1

Management of Dyspepsia

The patient's stomach upset should be evaluated during upper endoscopy. Consider:

• Proton pump inhibitor trial if gastritis/esophagitis found
• However, long-term PPI use can impair iron absorption - use lowest effective dose 1

Special Considerations for Diabetic Nephropathy

This patient has improving diabetic nephropathy (eGFR 66, improving microalbuminuria). While chronic kidney disease can cause anemia of chronic disease, the eGFR of 66 is not typically associated with significant erythropoietin deficiency 1. The microcytic pattern strongly favors iron deficiency over anemia of CKD, which is typically normocytic 1.