Workup for Iron Deficiency and Low Ferritin in a 20-Year-Old Male Cross-Country Runner
In a 20-year-old male cross-country runner with iron deficiency and low ferritin, obtain a complete blood count (CBC) with hemoglobin, hematocrit, mean cell volume (MCV), mean cell hemoglobin (MCH), and serum ferritin to confirm iron deficiency, then assess for gastrointestinal blood loss, dietary inadequacy, and hemolysis before initiating treatment.
Initial Laboratory Assessment
The baseline workup should include 1:
- Hemoglobin and hematocrit to determine if anemia is present (anemia defined as Hb <125 g/L in males)
- MCV and MCH to identify microcytosis and hypochromia
- Serum ferritin as the most established marker for iron stores
- Transferrin saturation (TSAT) when available, calculated as serum iron divided by total iron-binding capacity
Iron deficiency is defined as serum ferritin <35 μg/L with normal hemoglobin values 1. However, for athletes, particularly endurance athletes like cross-country runners, a ferritin threshold of 30 μg/L is more appropriate 2, with some evidence suggesting values <50 μg/L may be clinically relevant in athletes 3.
Distinguishing Iron Deficiency States
You need to determine whether this is:
- Iron deficiency without anemia: Low ferritin (<30-35 μg/L) with normal hemoglobin
- Iron deficiency anemia: Low ferritin (<35 μg/L) with hemoglobin <125 g/L
Both conditions warrant treatment in athletes, as iron deficiency even without anemia can negatively impact aerobic performance 1 due to iron's role in hemoglobin, myoglobin, and oxidative enzymes.
Identifying the Underlying Cause
In a young male athlete, iron deficiency is less common than in females (5-11% prevalence in male athletes vs 15-35% in females) 1, so identifying the cause is critical. Low iron status in athletes results from 1:
- Red cell hemolysis from repetitive foot strike (common in runners)
- Gastrointestinal bleeding (exercise-induced or pathologic)
- Inadequate dietary intake (particularly concerning if vegetarian/vegan diet)
Specific History to Obtain
- Dietary assessment: Daily iron intake, meat consumption, vegetarian/vegan diet
- GI symptoms: Abdominal pain, changes in stool, visible blood in stool
- Medication use: NSAIDs, aspirin (can cause GI bleeding)
- Training intensity: Recent increases in mileage or intensity
- Symptoms: Fatigue, reduced performance, lethargy
When to Pursue GI Evaluation
In young men, iron deficiency anemia warrants the same investigational algorithm as older adults 4 because the yield of pathology is considerably higher than in women of the same age. If IDA is confirmed and no obvious explanation exists from history, bidirectional endoscopy should be considered 5, particularly if:
- Hemoglobin is significantly reduced
- No clear dietary or training-related explanation
- GI symptoms are present
- No response to appropriate iron supplementation
For iron deficiency without anemia in a young male athlete, GI investigation may be deferred initially if there's a clear dietary or training-related explanation, but the threshold for investigation should be low 4.
Additional Testing Considerations
If ferritin is borderline or there's concern for inflammation (which can falsely elevate ferritin as an acute phase reactant):
- C-reactive protein (CRP) to exclude acute phase reaction 6
- Percent hypochromic red cells (if available) - values >10% indicate iron deficiency 7
- Reticulocyte hemoglobin content (if available) - direct assessment of functional iron availability 8
Monitoring Frequency
For male athletes, iron status assessment is reasonable once per year 1, but should be performed more frequently (every 6 months) when iron deficiency has been detected 1, 9.
Common Pitfalls to Avoid
- Don't assume low ferritin alone means you've found the cause - in young men, this is uncommon and warrants investigation for GI pathology
- Don't use WHO thresholds (ferritin <15 μg/L) - these miss many cases of iron deficiency in athletes 1, 2
- Don't check ferritin within 4 weeks of iron supplementation - circulating iron interferes with the assay 8
- Don't ignore iron deficiency without anemia - it still impairs aerobic performance in athletes 1, 3