Intravenous Iron Therapy is Indicated
For a 76-year-old woman with oral iron intolerance and laboratory evidence of iron deficiency (iron saturation 13%, rising RDW to 16.2), intravenous iron replacement is the appropriate management strategy. 1
Laboratory Interpretation
Your patient's labs demonstrate evolving iron deficiency despite stable hemoglobin:
- Iron saturation of 13% (below the 20% threshold for iron deficiency) 2, 3
- Rising RDW from 14.2 to 16.2 indicates increasing red cell size variability, characteristic of developing iron deficiency 2
- Decreasing MCHC from 33.0 to 31.1 reflects worsening hypochromia
- Modest improvement in serum iron and saturation (from 9% to 13%) suggests some response but remains inadequate
The stable hemoglobin/hematocrit is misleading—this patient has functional iron deficiency that will progress to anemia without intervention.
Why Intravenous Iron is Required
Oral iron intolerance is an absolute indication for IV iron therapy 1. The British Society of Gastroenterology guidelines explicitly state: "For those intolerant or not responding to oral iron, there are three parenteral preparations available" 1.
In elderly patients, oral iron frequently causes:
- Gastrointestinal upset (nausea, constipation, abdominal pain)
- Poor compliance
- Inadequate absorption due to age-related gastric changes 4
Specific IV Iron Recommendations
First-Line Options (in order of preference):
Ferric carboxymaltose (Ferinject): 1000 mg over 15 minutes 1, 5
- Most convenient single-dose option
- No test dose required
- Excellent safety profile (22-29% minor side effects, no reported anaphylaxis to date) 1
Iron isomaltoside (not available in US): Up to 1500 mg total dose infusion 5
- Only formulation FDA-labeled for total dose infusion
- Proven cardiovascular mortality benefit in heart failure 5
Iron sucrose (Venofer): 200 mg over 10 minutes 1
- Requires multiple doses (typically 5 doses = 1000 mg total)
- Lower cost per gram (£70.80 vs £217.50 for ferric carboxymaltose) 1
- No test dose required
Avoid:
- Iron dextran: Higher anaphylaxis risk (0.6-0.7%), 31 reported fatalities 1976-1996 1
Dosing Strategy
Calculate total iron deficit and administer as total dose infusion or divided doses:
For a 76-year-old short female (estimate 50 kg):
- Target hemoglobin: 12 g/dL
- If current Hb is stable at ~11-12 g/dL, give 1000 mg IV iron to replenish stores 1, 5
Critical point: The goal is not just correcting hemoglobin but replenishing iron stores to prevent recurrence 1.
Monitoring Protocol
Recheck labs 4-8 weeks after final infusion 5:
- Do NOT check iron parameters within 4 weeks (circulating iron interferes with assays)
- Expect hemoglobin increase of 1-2 g/dL within 4-8 weeks 5
- Target ferritin >50 ng/mL (>100 ng/mL if inflammation present) 5
- Target transferrin saturation >20% 6, 3
Essential Concurrent Actions
Screen for coeliac disease if not already done—present in 2-6% of patients with iron deficiency 1, 7
- Tissue transglutaminase antibody (tTG)
- Consider upper endoscopy with duodenal biopsies
Evaluate for occult GI blood loss given her age:
Check renal function—chronic kidney disease is common at this age and affects iron metabolism 3
Safety Precautions
All IV iron formulations require:
- Resuscitation facilities available 1
- 30-minute observation post-infusion
- Avoid rapid infusion (increases reaction risk) 8
Common minor reactions (20-30%): headache, nausea, myalgias—self-limited 1, 5
Common Pitfall to Avoid
Do not wait for anemia to develop before treating. Your patient has iron deficiency with stable hemoglobin NOW—the rising RDW and low iron saturation indicate exhausted iron stores and impending anemia 4, 9. Early IV iron prevents progression and improves quality of life even in non-anemic iron deficiency 4.