In a 22-year-old woman on oral iron who needs a repeat prescription, what assessments and investigations should be performed in primary care before renewing the medication?

Management of Iron Prescription Renewal in a 22-Year-Old Woman

Before renewing iron therapy, you must check complete blood count, serum ferritin, and calculate transferrin saturation to confirm ongoing iron deficiency and assess treatment response. 1

Immediate Laboratory Assessment Required

Essential blood tests:

• Complete blood count (CBC) to assess hemoglobin, MCV, and MCH—these parameters determine whether anemia has resolved and whether microcytosis persists 1
• Serum ferritin to evaluate iron store repletion; target >100 ng/mL to prevent rapid recurrence 1
• Serum iron and total iron-binding capacity (TIBC) to calculate transferrin saturation (TSAT); values <16-20% confirm persistent iron deficiency requiring continued therapy 1

Expected therapeutic response if treatment has been adequate:

• Hemoglobin should have risen ≥10 g/L within the first 2 weeks of starting iron 1
• After hemoglobin normalizes, iron must continue for an additional 3 months to fully replenish stores 1

Clinical History to Obtain

Assess compliance and tolerance:

• Duration and consistency of iron intake—many patients discontinue prematurely once symptoms improve 1
• Gastrointestinal side effects (nausea, constipation, diarrhea) that may have limited adherence 1
• Dosing schedule used (daily vs. alternate-day)—alternate-day dosing improves absorption by 30-50% and reduces side effects 1

Identify ongoing iron loss:

• Menstrual blood loss pattern—heavy menses are the most common cause of iron deficiency in premenopausal women 1
• New gastrointestinal symptoms (abdominal pain, altered bowel habits, visible blood) that mandate urgent endoscopic evaluation 1
• Dietary history, particularly vegetarian/vegan diet, which increases risk of recurrence 1

Screening for Underlying Causes (If Not Previously Done)

Mandatory serologic screening:

• Tissue transglutaminase IgA antibodies for celiac disease—present in 3-5% of iron deficiency cases and causes treatment failure if missed 1
• Non-invasive Helicobacter pylori testing (stool antigen or urea breath test)—the organism impairs iron absorption 1

Reserve bidirectional endoscopy for:

• Age ≥50 years (higher malignancy risk) 1
• Gastrointestinal symptoms or strong family history of colorectal cancer 1
• Positive celiac or H. pylori testing requiring confirmation 1
• Failure to respond to adequate oral iron after 8-10 weeks 1

In a young, asymptomatic premenopausal woman with heavy menses and no alarm features, empiric iron supplementation without immediate endoscopy is appropriate. 1

Decision Algorithm for Prescription Renewal

If ferritin >100 ng/mL and hemoglobin normalized:

• Stop daily iron supplementation—continuing beyond store repletion is potentially harmful 1
• Schedule ferritin monitoring every 6-12 months to detect early recurrence, especially in menstruating women 1

If ferritin 30-100 ng/mL:

• Continue oral iron for an additional 3 months after hemoglobin normalization to reach target ferritin >100 ng/mL 1
• Prescribe ferrous sulfate 65 mg elemental iron daily or 60-65 mg every other day 1

If ferritin <30 ng/mL despite adequate treatment duration:

• Investigate for ongoing blood loss or malabsorption—check celiac and H. pylori serology if not already done 1
• Consider switching to intravenous ferric carboxymaltose (15 mg/kg, max 1000 mg per dose) if oral intolerance, malabsorption, or ongoing blood loss exceeding oral replacement capacity 1

If hemoglobin failed to rise ≥10 g/L within 2 weeks:

• Urgent evaluation required—this suggests malabsorption, non-compliance, or ongoing blood loss 1
• Proceed with celiac/H. pylori screening and consider endoscopy if age ≥50 or alarm symptoms present 1

Optimal Iron Prescription

First-line oral therapy:

• Ferrous sulfate 200 mg tablet (65 mg elemental iron) once daily, or every other day if gastrointestinal side effects occurred 1
• Alternate-day dosing increases fractional absorption and reduces side effects compared to daily dosing 1
• Take on empty stomach for optimal absorption, or with meals if gastrointestinal symptoms occur 1

Alternative formulations if ferrous sulfate not tolerated:

• Ferrous fumarate 210 mg (69 mg elemental iron) or ferrous gluconate 300 mg (37 mg elemental iron) 1
• Ferric maltol (newer formulation with comparable gastrointestinal tolerability to placebo) 1

Critical Pitfalls to Avoid

• Do not renew iron without checking ferritin—you cannot determine whether stores are replete or whether ongoing supplementation is needed 1
• Do not assume normal hemoglobin means adequate iron stores—ferritin lags behind hemoglobin recovery by 3-6 months 1
• Do not continue daily iron indefinitely once ferritin >100 ng/mL—this risks iron overload 1
• Do not overlook celiac disease screening—its 3-5% prevalence in iron deficiency makes it a frequent cause of treatment failure 1
• Do not delay endoscopy in patients ≥50 years or with alarm symptoms—gastrointestinal malignancy can present solely with iron deficiency 1