Hospital-acquired anemia (HAA) is common in patients with acute myocardial infarction (AMI) admitted with normal hemoglobin level, is associated with greater mortality and worse health status, and commonly occurs in the absence of recognized bleeding. Salisbury et al studied whether diagnostic blood loss from phlebotomy, a potentially modifiable risk factor, was associated with HAA in 17 676 patients with incident AMI from 57 US hospitals. Moderate to severe HAA developed in 1 in 5 patients, and these patients experienced greater intensity of diagnostic phlebotomy than patients who did not (mean [SD] 173.8 [139.3] mL v. 83.5 [52.0] mL; P < .001). After adjusting for potential confounders, each 50 mL of diagnostic blood loss was associated with a 15% higher risk of developing HAA. Strategies that reduce diagnostic blood loss, including greater use of pediatric blood tubes in adult patients, more frequent use of stored serum samples, and efforts to group blood draws for laboratory tests to eliminate unnecessary blood draws, should be studied to understand whether reducing diagnostic blood loss prevents HAA and improves clinical outcomes.