Marathoner with Low Ferritin, Normal Hemoglobin, and a Blood-Donation Habit
Priya, 26, is training for her second marathon at 70–80 km/week, with two threshold sessions weekly. She is 58 kg, 168 cm, BMI 20.5. She reports 3 months of worsening fatigue, frequent colds, and a 2-second decline in her 5 km time despite good training consistency. Her GP ordered bloodwork: ferritin 14 ng/mL (ref 15–150), hemoglobin 12.9 g/dL, MCV 84 fL, CRP mildly elevated at 6 mg/L. She eats a mostly plant-based diet with eggs and fish twice weekly. Her typical day: coffee with breakfast (which includes a calcium-fortified cereal and an iron tablet prescribed by her GP), a salad lunch with spinach and chickpeas, and dinner after her evening run. She has heavy menstrual periods (5–6 days) and donates blood twice yearly because her workplace runs drives. She takes no other medication and has no GI symptoms.
1. Her GP says the ferritin is 'borderline but fine' because hemoglobin is normal. Explain what the labs likely indicate and why normal hemoglobin does not rule out a problem for her.
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Normal hemoglobin does not exclude iron deficiency in a training athlete, because stores are depleted before erythropoiesis is impaired - ferritin falls first, then MCV/MCH, then hemoglobin. Three things make her result more serious than the number suggests. First, ferritin is an acute-phase protein, and her CRP of 6 mg/L means the true value is lower than 14 ng/mL; ferritin should be read alongside CRP, not in isolation. Second, ferritin 14 with symptoms (fatigue, recurrent infections, declining performance) is functionally deficient for an endurance athlete even though the lab's reference range begins at 15. Third, an MCV of 84 fL sits at the low end - a trend worth watching, not a reassuring value. What you cannot do is diagnose iron deficiency anemia or decide on supplementation. The coach's job is to flag the pattern, explain it, and ask her to take the results back to her GP along with the training context (weekly volume, donation history, menstrual loss) the GP may not have. Retesting after 8–12 weeks of change is the relevant follow-up window.
2. List the factors in Priya's history that plausibly impair iron status or absorption, and rank them by how much you would prioritize addressing each. Justify the ranking.
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The factors, ranked by likely magnitude and coachability:
- Blood donation twice yearly. Each whole-blood donation removes roughly 200–250 mg of iron - comparable to many months of menstrual loss - and donation centers often accept donors with low-normal ferritin. Highest priority because it is binary and immediately stoppable.
- Heavy menstrual bleeding, 5–6 days. High impact, essentially no coach control; this is a GP conversation about a heavy-flow workup, not a nutrition fix.
- Iron taken with coffee and a calcium-fortified cereal. Polyphenols and calcium both inhibit non-heme absorption when co-ingested. Easy, same-week fix: move the tablet, separate it from coffee and calcium by about two hours, pair with a vitamin C source.
- Low heme iron intake. Fish twice weekly means most iron is non-heme and less bioavailable; she needs absorption-enhancing pairings and a higher total intake, not just 'more spinach.'
- Exercise-induced hepcidin elevation. Iron taken soon after a hard run is absorbed poorly; on training days the tablet belongs earlier, away from the session.
The ranking logic: prioritize what is large in magnitude, within her control this week, and not a clinical decision. Donation and timing outrank diet composition because they are reversible immediately and do not require anyone's permission.
3. She asks whether she should switch to a higher-dose iron supplement and take it with orange juice. What do you say, and what do you refer?
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Split the question. The orange juice is yours: vitamin C taken with the tablet is a reasonable way to improve non-heme absorption, and separating the iron from coffee and the calcium-fortified cereal is a legitimate coaching change you can make today.
The dose is not yours. Recommending a specific milligram amount - especially above what her GP prescribed - is prescribing: outside scope and potentially harmful (GI distress, constipation, masking another cause of the fatigue, and poor response while inflammation is elevated). The correct move is to report the change rather than authorize it: "Your GP put you on a specific dose. Before we touch it, send them these labs and the four factors we identified and ask whether the dose or the timing should change." Give her a short written summary so the conversation actually happens.
Then set follow-up: GI tolerance, a symptom log, ferritin and CRP retested at 8–12 weeks, and a request that she hold off donating blood until her GP clears her and stores have recovered.