How should I manage a 14‑year‑old female with iron deficiency (iron saturation 13 %, ferritin 11 ng/mL, serum iron 49 µg/dL)?

Management of Iron Deficiency in a 14-Year-Old Female

Start oral iron supplementation immediately with ferrous sulfate 325 mg daily (or every other day for better tolerance), evaluate for underlying causes including menstrual blood loss and dietary intake, and recheck iron studies in 8-10 weeks. 1, 2

Diagnostic Confirmation

This patient has clear-cut iron deficiency based on her laboratory values:

• Ferritin of 11 ng/mL is well below the diagnostic threshold for iron deficiency. While the AGA recommends a ferritin cutoff of 45 ng/mL for diagnosing iron deficiency in anemic patients 1, and some sources suggest 30 µg/L for healthy females >15 years 3, this patient's ferritin of 11 ng/mL is unequivocally low by any standard 1, 4
• Iron saturation of 13% confirms iron deficiency (normal transferrin saturation should be ≥20%) 4, 5
• The serum iron of 49 µg/dL is also low, supporting the diagnosis 1

Identify Underlying Causes

Evaluate specifically for:

• Heavy or prolonged menstrual bleeding – the most common cause in adolescent females, affecting up to 39% of premenopausal women with iron deficiency 1
• Dietary iron intake assessment – particularly important if she follows vegetarian/vegan diets, which rely exclusively on nonheme iron with decreased bioavailability requiring increased total iron intake 2
• Celiac disease screening – found in 3-5% of iron deficiency cases and should be screened serologically 1
• Eating disorders or restrictive eating patterns – common in adolescents and a high-risk factor for iron deficiency 2
• Athletic participation – adolescent athletes are more sensitive to changes in iron status and have increased iron needs 2

First-Line Treatment: Oral Iron Supplementation

Prescribe ferrous sulfate 325 mg daily, with the following optimization strategies:

• Administer once daily, ideally in the morning on an empty stomach for maximum absorption 1, 2
• Alternate-day dosing (every other day) improves absorption and reduces gastrointestinal side effects, which affect approximately 50% of patients and decrease adherence 1, 5
• Take with 500 mg vitamin C to enhance absorption, even if calcium or fiber is present 1
• Avoid taking with meals initially, but if gastrointestinal side effects occur (nausea, abdominal pain, constipation), taking with food is acceptable despite reduced absorption 1
• Continue treatment for at least 3 months to reach a target ferritin of 20 ng/mL before discontinuation 2

Alternative oral iron formulations (ferrous fumarate, ferrous gluconate, ferrous bisglycinate) may be better tolerated but are often more expensive, with no substantial evidence that any one product is superior 1

Monitoring Response to Treatment

Recheck complete blood count and iron studies (hemoglobin, ferritin, iron saturation) in 8-10 weeks:

• A hemoglobin rise ≥10 g/L within 2 weeks is highly suggestive of response to iron therapy 1
• Earlier assessment at 2-4 weeks can confirm adequate response if there are concerns about adherence or absorption 5
• If ferritin remains low after 8-10 weeks, consider intermittent oral supplementation for long-term maintenance 3

When to Consider Intravenous Iron

Intravenous iron should be considered if:

• Persistent iron deficiency despite a full course of oral iron (indicating malabsorption or intolerance) 2, 4
• Severe and/or symptomatic anemia requiring rapid repletion 2
• Ongoing blood loss that cannot be controlled (e.g., refractory heavy menstrual bleeding) 1
• Chronic inflammatory conditions such as inflammatory bowel disease, which impair gastrointestinal iron absorption 1, 2
• Oral iron intolerance with significant gastrointestinal side effects preventing adherence 4, 5

Intravenous iron has demonstrated efficacy and safety in adolescents and is increasingly used in this population 2

Address Menstrual Blood Loss

If heavy menstrual bleeding is identified as the cause:

• Treat the underlying menstrual disorder to reduce ongoing blood loss 6
• Consider hormonal contraception or other menstrual suppression strategies in consultation with gynecology if appropriate
• Ensure iron supplementation continues during treatment of the bleeding disorder 1

Dietary Counseling

Provide specific nutritional guidance:

• Increase dietary heme iron intake from meat, poultry, and fish, which has superior bioavailability compared to plant-based nonheme iron 1, 2
• For vegetarians/vegans, emphasize iron-rich plant foods (legumes, fortified cereals, dark leafy greens) and note that total iron intake requirements are higher 2
• Identify and avoid iron absorption inhibitors such as tea, coffee, and calcium supplements taken with iron-rich meals 1
• Nutritional consultation may be helpful to optimize dietary iron intake, particularly in complex cases 1

Long-Term Follow-Up

For patients with recurrent iron deficiency:

• Repeat iron studies every 6-12 months to monitor iron stores 3
• Intermittent oral iron supplementation may be needed to preserve iron stores in those with ongoing risk factors 3
• Long-term daily oral iron in the presence of normal or high ferritin is not recommended and is potentially harmful 3

Common Pitfalls to Avoid

• Do not delay treatment while waiting for extensive gastrointestinal evaluation in an adolescent female with an obvious cause (menstrual blood loss) 1
• Do not prescribe excessive elemental iron doses (>50 mg), as this increases side effects without improving absorption 3
• Do not assume normal ferritin rules out iron deficiency in the presence of inflammation; check transferrin saturation or C-reactive protein 1
• Do not discontinue iron supplementation prematurely before ferritin reaches at least 20 ng/mL, as this leads to rapid recurrence 2