
C1 Esterase Inhibitor









The C1 Esterase Inhibitor test checks the level of a protein called C1 esterase inhibitor in blood. This protein helps control inflammation and the immune system. Low or abnormal levels can lead to certain types of angioedema, which causes sudden swelling in areas like the face, hands, stomach, or throat.













Understanding C1 Esterase Inhibitor
C1 esterase inhibitor (C1-INH) is a protein made by the liver that helps control the immune system and prevent too much inflammation. It blocks substances in the blood that can trigger swelling. If the body does not make enough of this protein, or if it does not work properly, it can lead to conditions like hereditary angioedema (HAE) or acquired angioedema (AAE). These conditions cause sudden and sometimes serious swelling in areas like the face, hands, stomach, or throat.
The C1 Esterase Inhibitor test checks how much C1-INH protein is in the blood. The doctor may suggest this test for cases of repeated swelling without a clear cause, especially if there is no rash or if there is a family history of similar symptoms. The test helps evaluate HAE (often along with a functional C1-INH test and C4) where either the protein is low or does not function properly. It is often done along with a C4 complement test to confirm the diagnosis. Finding these problems early can help doctors start treatment and lower the risk of serious issues like airway swelling (which can be life-threatening).
No special preparation is required for the C1 Esterase Inhibitor test. Inform the doctor about all the medications and supplements currently being taken, as some of them may affect the test results, potentially requiring dosage adjustments or temporary discontinuation before the test.
Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. Do not self-medicate and always consult a doctor to understand the test results correctly.
Please note: This is an outsourced test. The sample for this test is collected by TATA 1MG and processed at a NABL accredited partnered lab.
What does C1 Esterase Inhibitor measure?
The C1 Esterase Inhibitor is a blood test that measures the levels of C1 esterase inhibitor (C1-INH) protein. This test helps assess whether there is a deficiency or dysfunction of this protein, which can lead to episodes of swelling, also known as angioedema.





FAQs related to C1 Esterase Inhibitor
- Kerrigan MJ, Naik P. C1 Esterase Inhibitor Deficiency. [Updated 2023 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from:
- C1 esterase inhibitor (human). P T. 2010 Jul;35(7 Section 2):2-3. PMID: 20689622; PMCID: PMC2912001. [Accessed 08 Aug. 2025]. Available From:
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