Why does the patient still have low ferritin five months after a resolved 7‑day episode of melena?

Why Ferritin Remains Low Five Months After Resolved Melena

A single 7-day episode of melena five months ago depleted your patient's iron stores, and ferritin remains low because iron stores take 3–6 months to replenish even after bleeding stops—and that assumes the patient has been taking adequate iron supplementation, which may not have occurred. 1

Understanding the Timeline of Iron Store Depletion and Recovery

Why Melena Causes Persistent Low Ferritin

• A week of melena represents significant gastrointestinal blood loss that depletes body iron stores rapidly, with each 500 mL of blood loss removing approximately 250 mg of iron from total body stores. 2
• Ferritin reflects storage iron in the liver, spleen, and bone marrow reticuloendothelial cells—it is the last compartment to recover after blood loss because the body prioritizes maintaining hemoglobin for oxygen delivery over replenishing storage iron. 3
• Even after bleeding stops, iron supplementation must continue for 3 months after hemoglobin normalizes to fully replenish iron stores, meaning a patient who stopped bleeding 5 months ago should only now be approaching normal ferritin if they adhered to proper supplementation. 1

The Three-Stage Progression of Iron Recovery

1. Stage 1 (Weeks 0–2): Hemoglobin rises by approximately 10–20 g/L as the body mobilizes any remaining iron stores and increases dietary absorption. 2
2. Stage 2 (Weeks 2–8): Hemoglobin normalizes, but ferritin remains low because absorbed iron is directed toward red blood cell production rather than storage. 1
3. Stage 3 (Months 3–6): Only after hemoglobin is stable does excess absorbed iron begin replenishing ferritin stores, requiring continued supplementation throughout this period. 1

Most Likely Explanations for Persistent Low Ferritin

Inadequate or Absent Iron Supplementation

• The most common reason ferritin remains low 5 months post-bleeding is that the patient never received or did not adhere to oral iron therapy. 1
• Without supplementation, dietary iron alone (10–15 mg/day absorbed) cannot replenish the 500–1000 mg deficit created by significant GI bleeding within a reasonable timeframe. 2
• Even patients who started iron therapy often discontinue it prematurely once hemoglobin normalizes, unaware that ferritin requires an additional 3 months of supplementation to reach target levels >100 ng/mL. 1

Ongoing Occult Blood Loss

• If ferritin continues falling or fails to rise despite adequate oral iron (65 mg elemental iron daily for 8–10 weeks), suspect ongoing occult GI bleeding. 1
• Causes include undiagnosed peptic ulcer disease, angiodysplasia, inflammatory bowel disease, or malignancy—all of which can produce intermittent blood loss below the threshold of visible melena. 1
• In adults >50 years or those with alarm symptoms (abdominal pain, weight loss, change in bowel habits), bidirectional endoscopy is mandatory to exclude GI malignancy. 1

Malabsorption Preventing Iron Store Repletion

• Celiac disease is present in 3–5% of iron-deficiency cases and should be screened with tissue transglutaminase antibodies, as it can cause treatment failure even with adequate supplementation. 1
• Helicobacter pylori infection impairs iron absorption and should be tested non-invasively (stool antigen or urea breath test). 1
• Post-bariatric surgery anatomy, atrophic gastritis, or proton-pump inhibitor use can all reduce iron absorption sufficiently to prevent ferritin recovery. 2

Immediate Diagnostic and Management Algorithm

Step 1: Confirm True Iron Deficiency and Assess Severity

• Measure transferrin saturation (TSAT) immediately; a TSAT <16–20% confirms iron deficiency and indicates insufficient iron is available for erythropoiesis. 3
• Check complete blood count to assess for microcytic anemia (low MCV, low MCH), which develops when iron deficiency progresses beyond store depletion. 1
• Ferritin <15 μg/L has 99% specificity for absolute iron deficiency; ferritin 15–30 μg/L indicates depleted stores requiring treatment. 1

Step 2: Initiate or Optimize Iron Supplementation

• Start oral ferrous sulfate 65 mg elemental iron daily (or 60–65 mg every other day) immediately—alternate-day dosing improves absorption by 30–50% and reduces gastrointestinal side effects. 1
• Expected response: hemoglobin should rise ≥10 g/L within 2 weeks; if no improvement occurs, suspect malabsorption, non-compliance, or ongoing blood loss. 1
• Continue supplementation for 3 months after hemoglobin normalizes to achieve target ferritin >100 ng/mL, which ensures adequate iron stores and prevents rapid recurrence. 1

Step 3: Screen for Malabsorption and Ongoing Blood Loss

• Order tissue transglutaminase IgA antibodies to screen for celiac disease—this is mandatory because celiac disease accounts for 3–5% of iron-deficiency cases and causes treatment failure if missed. 1
• Perform non-invasive H. pylori testing (stool antigen or urea breath test) because the organism impairs iron absorption. 1
• Reserve bidirectional endoscopy (upper GI gastroscopy + colonoscopy) for:
  • Age ≥50 years (higher malignancy risk)
  • Presence of GI symptoms (abdominal pain, altered bowel habits, visible blood)
  • Positive celiac or H. pylori testing requiring confirmation
  • Lack of response to adequate oral iron after 8–10 weeks
  • Strong family history of colorectal cancer 1

Step 4: Consider Intravenous Iron for Specific Indications

• Switch to intravenous ferric carboxymaltose (15 mg/kg, maximum 1000 mg per dose) when:
  • Oral iron intolerance (marked nausea, constipation, diarrhea)
  • Malabsorption (celiac disease, IBD, post-bariatric surgery)
  • Ongoing blood loss exceeding oral replacement capacity
  • Chronic inflammatory conditions (CKD, heart failure, cancer)
  • Pregnancy in second/third trimester 1
• IV iron produces reticulocytosis within 3–5 days and yields a mean hemoglobin increase of approximately 8 g/L over 8 days, demonstrating superior efficacy in indicated populations. 1

Critical Pitfalls to Avoid

• Do not assume ferritin will normalize spontaneously after bleeding stops—without supplementation, dietary iron alone cannot replenish stores within a clinically acceptable timeframe. 1
• Do not discontinue iron therapy once hemoglobin normalizes—this is the most common error, as ferritin requires an additional 3 months of supplementation to reach target levels >100 ng/mL. 1
• Do not overlook celiac disease screening—its 3–5% prevalence in iron-deficiency cases means missing this diagnosis leads to treatment failure and persistent symptoms. 1
• Do not delay endoscopy in high-risk patients (age ≥50, alarm symptoms, treatment failure)—GI malignancy can present with iron deficiency as the sole manifestation. 1

Follow-Up and Monitoring

• Recheck CBC and ferritin at 8–10 weeks to assess response to oral iron therapy. 1
• If ferritin fails to rise or continues falling despite adequate supplementation, this indicates ongoing blood loss or malabsorption requiring urgent GI evaluation. 1
• For patients with recurrent low ferritin (menstruating females, vegetarians, athletes), schedule ferritin screening every 6–12 months to detect early depletion before anemia develops. 1