A 28-year-old male triathlete noticed his performance was deteriorating. Blood tests confirmed he had iron deficiency and endoscopy showed this was due to slow hidden bleeding from the stomach from excess use of non-steroidal anti-inflammatory drugs he’d taken for pain relief, as well as increased iron demands due to high intensity training. Treatment included intravenous iron infusion over 15 minutes, repeated after one week. He was given medication for his stomach, increased his consumption of iron-rich foods (especially animal sources) and had follow-up blood tests to check for recurrence. He noted improvement in fitness, strength and endurance soon after the second infusion.