Ferritin 18 μg/L in a 66-Year-Old Male: Clinical Implications
A ferritin level of 18 μg/L in a 66-year-old male indicates iron deficiency with depleted iron stores that requires immediate investigation for the source of iron loss and initiation of iron supplementation. 1
Diagnostic Interpretation
Ferritin 18 μg/L falls within the 15-30 μg/L range, which indicates low body iron stores and generally warrants treatment. 1
While ferritin <15 μg/L has 99% specificity for absolute iron deficiency, values between 15-30 μg/L still represent depleted iron stores requiring intervention. 1, 2
This ferritin level is below the optimal diagnostic threshold of 30 μg/L, which provides significantly higher sensitivity for detecting iron deficiency with only minimal reduction in specificity. 3
In elderly patients specifically, ferritin values up to 45 μg/L increase the likelihood of iron deficiency, with values of 18 μg/L conferring a likelihood ratio of 41.47 for iron deficiency. 4
Critical Next Steps: Mandatory Investigation
In a 66-year-old male, iron deficiency must be considered gastrointestinal blood loss until proven otherwise, requiring urgent bidirectional endoscopy. 1, 2
Immediate Workup Required:
Bidirectional endoscopy (colonoscopy and upper endoscopy) is mandatory given age >50 years and higher risk of gastrointestinal malignancy. 1
Non-invasive testing for H. pylori (stool antigen or urea breath test) should be performed, as it is present in a significant proportion of iron deficiency cases. 1
Celiac disease serologies (tissue transglutaminase antibodies) should be obtained, as celiac disease is present in 3-5% of iron deficiency cases. 1
Complete blood count to assess for anemia and mean cell volume. 1
Transferrin saturation calculation (if serum iron and TIBC available) to confirm iron deficiency, with TSAT <16-20% confirming the diagnosis. 1, 2
Red Flags Requiring Urgent Evaluation:
Any gastrointestinal symptoms (abdominal pain, change in bowel habits, blood in stool) require urgent evaluation. 1
Age >50 years alone is sufficient indication for urgent GI evaluation due to higher risk of malignancy. 1
Clinical Significance and Symptoms
Iron deficiency at this level can cause significant symptoms even without anemia, including fatigue, lethargy, reduced exercise tolerance, difficulty concentrating, irritability, and restless legs syndrome. 1, 5
Approximately 32-40% of patients with iron deficiency experience restless legs syndrome, and 40-50% may have pica. 5
The patient may be asymptomatic, but symptoms should be specifically queried as they significantly impact quality of life. 5
Treatment Protocol
Immediate Iron Supplementation:
Initiate oral iron supplementation immediately without waiting for investigation results. 1, 2
Recommended regimen: Ferrous sulfate 325 mg daily or ferrous bisglycinate 30-60 mg elemental iron daily. 1
Alternate-day dosing (60 mg every other day) may improve absorption and reduce gastrointestinal side effects compared to daily dosing. 1
Take on empty stomach for optimal absorption, or with meals if gastrointestinal symptoms (constipation, nausea, diarrhea) occur. 1
Follow-Up and Monitoring:
Repeat CBC and ferritin in 8-10 weeks to assess response to treatment. 1
Target ferritin >100 μg/L to restore iron stores and prevent recurrence. 1, 2
Failure to respond to adequate oral iron therapy after 8-10 weeks requires urgent GI evaluation and consideration of intravenous iron. 1
Consider Intravenous Iron If:
Oral iron intolerance or gastrointestinal side effects prevent compliance. 5
Malabsorption is identified (celiac disease, atrophic gastritis, post-bariatric surgery). 5
Ongoing blood loss is documented. 5
Chronic inflammatory conditions are present (though less common in this scenario). 5
Common Pitfalls to Avoid
Do not assume dietary insufficiency or benign causes in an elderly male—gastrointestinal pathology must be excluded. 1, 2
Do not delay endoscopy pending response to iron supplementation—malignancy screening cannot wait. 1
Do not overlook celiac disease, which can be easily missed without serologic screening and is present in 3-5% of iron deficiency cases. 1
Do not continue daily iron supplementation indefinitely once ferritin normalizes, as this is potentially harmful. 1
Check inflammatory markers (CRP or ESR) if ferritin interpretation is unclear, though at 18 μg/L, inflammation is unlikely to be masking the diagnosis. 1