C3 Compliment Blood

Has anyone had an abnormal C3 Compliment blood test? Mine was abnormal and yet my C4 was normal. What does that mean?

Complements are like the vanilla of the cake. The immune response just doesn't work without them. A cake without vanilla just is not very good. They play a important role in immunity and are decreased in autoimmunity. The range of normal in labs do not reflect the lower 5% of the population nor does it reflect the upper 5%. Thus it depends on how low and whether anything else is abnormal.