Angioedema is a clinical diagnosis, with no required testing in the ED.1,2,4 Leukocyte counts cannot reliably differentiate if an infection is present, as leukocytosis over 30,000 per cubic millimeter has been observed.98 C-reactive protein may be elevated in ACEi-mediated angioedema.1,4 Determining the specific type of angioedema involves specialized laboratory testing not available in the ED, including tryptase, C4, and C1-INH.1–4 These tests can be obtained in the outpatient setting and should not be routinely obtained in the ED, as they do not guide management. Here, C4A is linked to angioedema.