Complement C4
Complement C4 is a protein involved in the classical pathway of the complement immune system. It plays a role in fighting infections and clearing immune complexes from the body.
Category: Inflammation & Immune
Also known as: complement c4, c4, c4 complement, serum c4, Beta 1 E-globulin, komplement c4
Reference range: 10–40 mg/dL (Source: ABIM)
Standard unit: mg/dL
High values may indicate
High C4 levels may indicate acute inflammation or infection, as C4 can act as an acute phase reactant.
Low values may indicate
Low C4 levels may indicate systemic lupus erythematosus (SLE), hereditary angioedema (C4 is often chronically low), immune complex disease, glomerulonephritis, or liver disease.
Frequently asked questions
- What is a normal Complement C4 level?
- A typical reference range for Complement C4 is 10–40 mg/dL (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is Complement C4 measured in?
- Complement C4 is most commonly reported in mg/dL. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do Complement C4 reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track Complement C4 over time?
- Yes. Upload results from any lab and BloodId charts your Complement C4 over time against its reference range, so you can see whether the trend is rising, falling, or stable.
Related biomarkers
Source: MedlinePlus, U.S. National Library of Medicine
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