What is the treatment for iron deficiency anemia in a female patient with low ferritin, low TSAT, and mild anemia?

Treatment for Iron Deficiency in a Female Patient

This patient requires oral iron supplementation given her low ferritin (19 ng/mL) and low TSAT (20%), despite having hemoglobin in the normal range (14.5 g/dL), as she has clear iron deficiency that warrants treatment to prevent progression to anemia and improve quality of life. 1

Iron Status Assessment

Your patient demonstrates:

• Ferritin 19 ng/mL: Well below the recommended threshold of 45 ng/mL for diagnosing iron deficiency 1
• TSAT 20%: At the lower limit, indicating inadequate iron availability for erythropoiesis 1
• Normal hemoglobin (14.5 g/dL): This represents iron deficiency without anemia, which still requires treatment 1

The combination of low ferritin and borderline TSAT indicates depleted iron stores with early functional iron deficiency 1.

Treatment Approach

First-Line: Oral Iron Supplementation

Start with oral ferrous iron salts as the initial treatment modality 1. The most cost-effective and commonly used formulations include:

• Ferrous sulfate 2
• Ferrous fumarate 3
• Ferrous gluconate 4

Optimal Dosing Strategy

Prescribe 100-200 mg elemental iron daily, but consider alternate-day dosing for better absorption and tolerability 1:

• Alternate-day dosing (every other day) results in 21.8% fractional iron absorption versus 16.3% with consecutive daily dosing 5
• Daily dosing increases hepcidin production, which paradoxically reduces iron absorption from subsequent doses 5
• Lower doses (19-38 mg elemental iron) may be equally effective as higher doses for iron repletion 6

Single daily dosing is superior to divided doses: A single morning dose produces equivalent efficacy to split dosing while avoiding hepcidin-mediated absorption interference 5.

Administration Guidelines

To maximize absorption 1:

• Take iron on an empty stomach when possible
• If gastrointestinal side effects occur, take with meals (though this reduces absorption)
• Add 500 mg vitamin C to enhance absorption 1
• Avoid concurrent antacid use, which decreases storage iron by approximately 57 mg 6

Expected Response and Monitoring

Reassess iron parameters 8-10 weeks after initiating treatment 1:

• Hemoglobin should increase by 1-2 g/dL within 4-8 weeks 1
• Target ferritin ≥50 ng/mL in the absence of inflammation 1
• Target TSAT ≥20% 1

Do not check iron parameters earlier than 4 weeks after starting supplementation, as circulating iron interferes with assays 1.

When to Consider Intravenous Iron

Switch to IV iron if 1:

• Oral iron fails to improve iron stores after 8-10 weeks
• Gastrointestinal side effects prevent oral iron tolerance
• Rapid iron repletion is required
• Malabsorption conditions are present (celiac disease, inflammatory bowel disease, post-bariatric surgery) 1

IV formulations include ferric carboxymaltose (up to 1000 mg per infusion over 15 minutes) 7 or ferric derisomaltose (up to 1500 mg total dose infusion) 1.

Common Pitfalls to Avoid

• Don't ignore iron deficiency without anemia: Even with normal hemoglobin, low ferritin causes fatigue and impaired quality of life requiring treatment 1
• Don't prescribe excessive daily doses: Higher doses (>100 mg) increase side effects without improving efficacy due to hepcidin upregulation 5, 6
• Don't check labs too early: Ferritin levels are falsely elevated immediately after iron supplementation 1
• Don't supplement if ferritin is normal or high: Iron supplementation with normal/high ferritin is potentially harmful 1

Underlying Cause Investigation

While initiating iron replacement, evaluate for:

• Dietary iron intake adequacy (recommended 18 mg/day for premenopausal women) 1
• Heavy menstrual bleeding (most common cause in premenopausal women) 1
• Gastrointestinal blood loss if menstrual losses don't explain deficiency 1
• Malabsorption conditions including celiac disease and H. pylori infection 1