Complement C3 and C4

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New Member

Date Joined Mar 2014
Total Posts : 7
   Posted 10/28/2014 1:03 PM (GMT -6)   
Does anyone know the significance of gradually declining C3 and C4? My C4 has been at the very low end of normal since I started having labs drawn at the beginning of March and is now at the cutoff off being low. My C3 has also been low normal since March and is now low (decreased by 44). Does this mean anything? Waiting for other pending labs before I talk to my rheumy. I have UCTD, sicca and Raynauds.

Post Edited (ghlsd2224) : 10/28/2014 12:29:35 PM (GMT-6)

Elite Member

Date Joined Jul 2009
Total Posts : 14475
   Posted 10/28/2014 5:22 PM (GMT -6)   
I can't remember, but if you check out they explain lab results very well and what they indicate.
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New Member

Date Joined Oct 2014
Total Posts : 16
   Posted 10/28/2014 10:58 PM (GMT -6)   
this is what I found for you:

C3 and C4 are the most commonly measured complement components.

A complement test may be used to monitor patients with an autoimmune disorder and to see if treatment for their condition is working. For example, patients with active lupus erythematosus may have lower-than-normal levels of the complement proteins C3 and C4.

Complement activity varies throughout the body. For example, in patients with rheumatoid arthritis, complement activity in the blood may be normal or higher-than-normal, but much lower-than-normal in the joint fluid.

Additional conditions under which the test may be performed:

Fungal infections
Gram negative septicemia
Parasitic infections such as malaria
Paroxysmal nocturnal hemoglobinuria (PNH)

Normal Results

The normal range is 75-135 mg/dl (milligrams per deciliter).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean

Increased complement activity may be seen in:

Ulcerative colitis

Decreased complement activity may be seen in:

Bacterial infections (especially Neisseria)
Hereditary angioedema
Kidney transplant rejection
Lupus nephritis
Systemic lupus erythematosus
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