Hello~Have you had a recent infection or injury, sometimes the C3 can be elevated due to these factors. Also, if you have any autoimmune disorders, they possibly can be elevated. Elevated C4 can be due to many causes, I would suggest discussing these numbers with your physician, if he/she is not concerned, then I would not worry about it.
Yes, I agree. High c3 can be due to recent infection. Also, if you have any autoimmune disorders as mentioned as well like lupus. That's common if you have lupus. C3 and C4 are part of the 'complement system' which is part of our immune system. They are measures of proteins in your blood that help our antibodies fight off infection. Why were you given this blood test? Are they suspecting an autoimmune disorder for you? I wouldn't worry about your c4, it's in normal. Normal is normal. But yes, your c3 is elevated. When do you see your doctor to discuss this?