The C1 Esterase Inhibitor (C1-INH) test measures levels of this key immune protein, crucial for diagnosing Hereditary Angioedema (HAE) (causing sudden swelling) or acquired angioedema, and investigating unexplained inflammation or autoimmune issues, revealing low levels (HAE) or high levels (infection/inflammation). This blood test helps doctors manage conditions where the body lacks enough C1-INH, preventing swelling in extremities, face, gut, or throat, and it requires a simple blood draw