Complement C3 blood test in Chiswick

What the test measures

The complement system is a group of proteins in the blood that help the immune system destroy bacteria, clear damaged cells and remove immune complexes. C3 sits at the centre of the system, where all three activation pathways meet, so it is one of the most important complement proteins to measure. It is mainly made by the liver.

When the complement system is very active, as in some autoimmune and kidney conditions, C3 is used up faster than it is made and the level in the blood can fall. On the other hand, C3 is also an acute phase protein, which means it can rise during infection, inflammation or injury. The price includes the blood sample taken at our Chiswick clinic, analysis at the Randox accredited laboratory, a review of your result with an Omnia practitioner and a GP feedback report on request.

Who it is for

• You have a known autoimmune condition, such as lupus, and your clinician uses C3 to monitor activity.
• You have kidney inflammation or blood or protein in your urine, and complement levels have been suggested.
• You have frequent or unusual infections and want to look at your immune proteins.
• You have joint pain, rashes or tiredness and your practitioner is considering an autoimmune cause.
• Your specialist has asked for C3 and C4 to be tracked together.

Understanding your result

Your report shows your C3 with the laboratory reference range. A low C3 can suggest that complement is being consumed, which may happen in active lupus, some types of kidney inflammation, certain infections or, rarely, an inherited deficiency. Comparing C3 with C4 helps show which part of the system is involved.

A raised C3 is usually a sign of inflammation or infection and is not specific to any one condition. Complement results are interpreted with other tests, such as antibodies, kidney markers and urine checks, and with your symptoms. A result beyond the reference range is a signal to talk it through, not a diagnosis.

Preparing for your test

No fasting or special preparation is needed for C3. Let us know about any known autoimmune or kidney condition, recent infection, and the medicines you take, including steroids or immune-modifying treatments.

C3 is included in Advanced GP3, alongside other immune and inflammation markers. If you also have urine changes, our Kidney Health Check may help. A full list shows every blood test and price in Chiswick.

Questions

How much is a complement C3 test in Chiswick?

The complement component 3 (C3) test costs £79 at Omnia. That covers the sample at our W4 clinic, analysis at an accredited laboratory, a practitioner review and a GP feedback report on request.

Can a C3 test diagnose lupus?

No. Low complement can support the picture in lupus and helps monitor it, but the diagnosis depends on symptoms, examination and several other tests, usually under a rheumatologist.

Why test C3 and C4 together?

They are used by different parts of the complement system, so the pattern of the two results gives more information than either alone.

Can an infection affect my C3?

Yes. C3 often rises during infection or inflammation, so testing when you are well gives a clearer baseline.