© 2017 Wiley Periodicals, Inc. Introduction: Daily laboratory testing (DLT) is an important cause of iatrogenic anemia. Therapeutic plasma exchanges (TPE) represent another source of blood loss. This study investigated the contributions of DLT and TPE to changes in hemoglobin of inpatients with myasthenia gravis (MG) exacerbation. Study design and methods: All admissions for MG that included TPE between 2008 and 2012 were identified. The DLT- and TPE-related blood losses per patient were estimated based on the number of laboratory tests and TPE procedures. The primary endpoint was the difference between the discharge hemoglobin (Hgb) and the admission Hgb (ΔHgb). Univariate and multivariable analyses were used to identify clinical predictors of ΔHgb. Results: A total of 46 patients (52% male, average age of 58 years) had 90 hospitalizations and underwent 424 TPEs during the study-period. Their average length of stay (LOS) was 10.4 days, and total DLT and TPE-related blood losses were 107 and 94 mL, respectively. While 41% of patients were anemic on admission, 90% were anemic at discharge. The average ΔHgb was −2.2 g/dL. The patient's blood volume, renal function, admission number, LOS, and combined blood losses correlated with ΔHgb by linear regression, but only DLT was an independent predictor of ΔHgb in the multivariable analysis. Conclusion: Approximately 50% of MG patients admitted for TPE developed hospital-acquired anemia, which was directly correlated with the volume of blood collected for laboratory tests. A variety of strategies to reduce DLT could circumvent this iatrogenic complication.