Skip to content


    Attention All WebMD Community Members:

    These message boards are closed to posting. Please head on over to our new WebMD Message Boards to check out and participate in the great conversations taking place:

    Your new WebMD Message Boards are now open!

    Making the move is as easy as 1-2-3.

    1. Head over to this page:

    2. Choose the tag from the drop-down menu that clicks most with you (and add it to any posts you create so others can easily find and sort through posts)

    3. Start posting

    Have questions? Email us anytime at

    Includes Expert Content
    Low C4 (but C3 is normal)? really really confused please any advice
    Jalee85 posted:
    Hello I am new to this group. I technically have diagnosis of undifferentiated connective tissue disease. A mixture of Lupus/Scleroderma/ and SJorgens.
    I had a new test done last time I saw a doctor she tested my C3 and C4 my C4 was low not horribly low but in the low range my C3 was normal my CRP was also mildly elevated.
    I was just wondering everything I read says lupus it is usually your C3 & C4.
    I"m just wondering what is the norm for people with Lupus low C4 means disease activity doesn't it I'm not seeing my rheum again until June 1st.
    I have been chroncially sick since March of 2010. And have had other issues throughout the years I am a 25yr old female. and very confused?
    David Zelman, MD responded:
    C3 and C4 are blood proteins that are involved with the immune response. Lupus is a disease that involves immune hyprereactivity and thus levels of these proteins can be low in active lupus as they are consumed. C4 can be low without C3 also being low. Levels of these proteins are just a part of the overall assessment in lupus disease activity and by itself a low C4 does not necessarily mean active disease. Low C3 and C4 tends to be present with lupus kidney disease and widespread skin disease. Improvement with treatment often correlates with normalization of C3,C4
    David Zelman MD
    Jalee_85 responded:
    Well this is me somehow I can't log on to my old account I don't get it.. always use the same e-mail but I had another blood test for complement level and the C4 was yet again low while the C3 was not low and I found what I wish I wold of found back when I asked this question..

    Deficiency of certain complement molecules [especially C2, C4> increases the risk of developing SLE; these deficiencies run in families, ie can be inherited. Patients with active lupus erythematosus may have depressed levels of C3 and C4, and these component levels may be followed as a rough index of disease activity.
    nycorpsman responded:
    Hi Jalee,

    I too have been chronically sick since Spring 2009. I have low C4, mildly elevated ESR, CRP, and COMP 50 tests.

    I have tried several times to get the doctors to take my complaints seriously but in vain. I usually have to get hospitalized with an acute flare before they'll even give me pain meds.

    Just stay patient and try to document/take pics of any and all of your symptoms.

    You are not not alone, and you aren't imagining your symptoms. Just stay vigilant
    lupylisa44 replied to nycorpsman's response:
    The post you replied to is more than a year old. I suggest you start a new discussion.
    With love, with patience and with faith, we'll make our way.
    nycorpsman replied to lupylisa44's response:
    I was searching for answers to my abnormal labs and found this online. Her story seems so similar to mine that I had to reply.

    With Lupus

    WebMD's Day2Night will help you develop personal coping strategies for living with lupus – at home,
    at work, or with family
    and friends.
    Visit Lupus Day2Night

    Helpful Tips

    There is a big connection between stress and lupus. Although it doesn't actually cause lupus, it certainly exacerbates it. An article from ... More
    Was this Helpful?
    19 of 19 found this helpful

    Related Drug Reviews

    • Drug Name User Reviews

    Report Problems With Your Medications to the FDA

    FDAYou are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.