What is the appropriate treatment for a 17-year-old patient with iron deficiency anemia?

Treatment for Iron Deficiency Anemia in a 17-Year-Old

Start oral ferrous sulfate 200 mg once daily immediately, continue for 3 months after hemoglobin normalizes to replenish iron stores, and investigate for underlying causes including menstrual blood loss and celiac disease. 1

Immediate Iron Replacement Therapy

• Begin with oral ferrous sulfate 200 mg once daily as the first-line treatment for this adolescent with severe iron deficiency anemia (ferritin 7, iron saturation 6%, hemoglobin 10.7) 1, 2
• If gastrointestinal side effects occur, reduce to one tablet every other day, which maintains efficacy while improving tolerability 1, 3
• Alternative oral preparations include ferrous fumarate or ferrous gluconate if ferrous sulfate is not tolerated 1
• Do not delay iron therapy while awaiting investigations—treatment should begin immediately 1

The 2021 British Society of Gastroenterology guidelines specifically recommend starting with one tablet daily rather than the older three-times-daily regimen, as recent evidence shows similar efficacy with better tolerability 1. The elevated reticulocyte count (21.9) indicates the bone marrow is responding appropriately to the anemia, confirming this is primarily an iron supply problem rather than a production defect.

Monitoring Response to Treatment

• Check hemoglobin after 2-4 weeks—expect a rise of ≥10 g/L (≥1 g/dL) within 2 weeks if treatment is effective 1, 2
• A good response to iron therapy (Hb rise ≥10 g/L within 2 weeks) confirms absolute iron deficiency even when iron studies are equivocal 1
• Continue iron supplementation for 3 months after correction of anemia to fully replenish iron stores 1
• Monitor hemoglobin and MCV at 3-month intervals for one year, then again after another year 1

Investigation for Underlying Causes

Since this is a 17-year-old (likely premenopausal female given the age and severity of deficiency):

• Obtain detailed menstrual history—menstrual blood loss, especially menorrhagia, is the most common cause of iron deficiency in this age group 1, 2
• Heavy menstrual bleeding (≥80 mL/month) affects approximately 10% of women of childbearing age and is a major risk factor 1
• Screen for celiac disease with serology or small bowel biopsy at gastroscopy, as it is found in 3-5% of IDA cases 1
• Urinalysis to exclude hematuria as a rare cause of iron loss 1

Do not perform gastrointestinal endoscopy in a premenopausal adolescent unless:

• There is no menstrual blood loss to explain the deficiency 1
• Hemoglobin fails to normalize with adequate iron replacement 1
• There are gastrointestinal symptoms or rectal bleeding 1
• IDA recurs despite adequate treatment 1

Men and postmenopausal women require bidirectional endoscopy (gastroscopy and colonoscopy) as first-line investigation 1, 4, but this is not appropriate for a menstruating 17-year-old without other concerning features.

When to Consider Intravenous Iron

Switch to intravenous iron if: 1, 5, 2

• No hemoglobin response after 3-4 weeks of adequate oral therapy
• Ongoing heavy menstrual bleeding that exceeds oral iron absorption capacity
• Oral iron intolerance despite dose reduction or alternative preparations
• Malabsorption is identified (celiac disease)

For IV iron, typical dosing is 200 mg undiluted as slow IV injection over 2-5 minutes or diluted in 100 mL normal saline over 15 minutes 6

Common Pitfalls to Avoid

• Do not use three-times-daily dosing as the initial regimen—this outdated approach increases side effects without improving efficacy 1, 3
• Do not stop iron when hemoglobin normalizes—continue for 3 months to replenish stores 1
• Do not perform extensive gastrointestinal workup in menstruating adolescents before addressing menstrual blood loss 1
• Do not check ferritin during acute inflammation—it may be falsely elevated as an acute phase reactant 5, 7