Treatment of Iron Deficiency Anemia in a Patient with a G-Tube
Intravenous iron therapy should be the first-line treatment for iron deficiency anemia in patients with G-tubes, as compromised gastrointestinal absorption makes oral iron ineffective regardless of the administration route. 1
Why IV Iron is Preferred Over Oral Iron (Even Through G-Tube)
The presence of a G-tube indicates underlying gastrointestinal pathology that likely impairs iron absorption, making oral iron supplementation—whether by mouth or through the tube—inadequate for correcting iron deficiency anemia 1
IV iron demonstrates superior efficacy with an odds ratio of 1.57 for achieving a 2.0 g/dL hemoglobin rise compared to oral iron, and has significantly better tolerability with an odds ratio of 0.27 for treatment discontinuation 2
Oral iron absorption is tightly regulated and limited even in healthy individuals, and any gastrointestinal dysfunction (the reason for G-tube placement) further compromises this already inefficient process 1
Specific IV Iron Dosing Protocol
For patients ≥50 kg: Administer ferric carboxymaltose 750 mg IV on two occasions separated by at least 7 days, for a total cumulative dose of 1,500 mg per course 3
For patients <50 kg: Administer 15 mg/kg body weight IV in two doses separated by at least 7 days 3
Alternative single-dose regimen: In adults, 15 mg/kg up to a maximum of 1,000 mg IV may be given as a single dose per course 3
Ferritin Interpretation in This Context
If the patient has any concurrent inflammation (common with conditions requiring G-tubes), ferritin levels up to 100 μg/L may still indicate iron deficiency, as ferritin is an acute-phase reactant that rises artificially during inflammation 1, 2
In the absence of inflammation, ferritin <30 μg/L confirms iron deficiency, but with inflammation present, use the 100 μg/L threshold 1
Check C-reactive protein to assess for inflammation when interpreting ferritin levels to avoid false-negative results 4
Monitoring Response to Treatment
Recheck complete blood count and ferritin in 3-4 weeks after IV iron administration, with expected hemoglobin rise of approximately 2 g/dL if treatment is adequate 2
Target ferritin levels should be maintained above 100 μg/L to prevent rapid recurrence of anemia 1
Re-treatment with IV iron should be initiated when ferritin drops below 100 μg/L or hemoglobin falls below 12 g/dL (women) or 13 g/dL (men) 1
Critical Safety Monitoring
Check serum phosphate levels before any repeat course of IV iron, especially if repeat treatment occurs within 3 months, as hypophosphatemia is a known complication of ferric carboxymaltose 3
Hypophosphatemia occurs in approximately 51% of patients receiving ferric carboxymaltose, with 13% developing profound hypophosphatemia (<0.32 mmol/L) 5
Hypophosphatemia severity correlates with FCM dose and may persist for an average of 6 months, potentially causing persistent fatigue despite anemia correction 5
Treat hypophosphatemia as medically indicated if it develops 3
When Oral Iron Through G-Tube Might Be Considered
Oral iron through the G-tube should only be considered if:
- The underlying disease is in complete remission with no inflammation 1
- The anemia is mild (Hb 11.0-12.9 g/dL in men, 11.0-11.9 g/dL in women) 1
- There is no history of previous intolerance to oral iron 1
If oral iron is attempted, limit to no more than 100 mg elemental iron per day to minimize gastrointestinal side effects and maximize absorption 1
Common Pitfalls to Avoid
Do not assume the G-tube provides better iron absorption than oral intake—the underlying GI pathology is the limiting factor, not the route of administration 1
Do not use oral iron as first-line therapy in patients with hemoglobin <10 g/dL, as IV iron is specifically indicated in this population 1
Do not overlook the need to address the underlying cause of iron deficiency, as treating the source of blood loss or malabsorption is essential for long-term management 1