All tests › Inflammation and immune system

C1 esterase inhibitor

Inflammation and immune system · also printed as C1 inhibitor, C1-INH, C1 esterase inhibitor level, C1 inhibitor level, C1 INH

Typical UK adult range0.21 to 0.39 g/L

Ranges vary between laboratories; the range printed on the report takes precedence.

What this test measures

C1 esterase inhibitor is a protein that controls part of the complement and swelling pathways. A low level or a non-working protein causes hereditary angioedema, with episodes of deep swelling.

Why doctors request it

Requested for recurrent swelling of the face, limbs, gut or throat without hives, and in relatives of someone with hereditary angioedema.

What commonly pushes it up

Inflammation, slightly

What commonly pushes it down

Hereditary angioedema, inherited
Acquired deficiency with some blood disorders
Oestrogen-containing contraception, slightly

Everyday reasons for a value outside the range

The level can be normal while the protein does not work, so a function test is often run as well
C4 is usually low alongside

About the sample

No fasting needed. Read with C4 and the function test.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

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This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.