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McMaster Textbook of Internal Medicine

Complement, Total (CH50), C3, and C4

How to Cite This Chapter: Don-Wauchope A, Chetty VT, Ivica J, Kavsak P, Khan WI, Lafreniere M, Nouri K, Solnica B. Complement, Total (CH50), C3, and C4. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. https://empendium.com/mcmtextbook/chapter/B31.1269.3.7.184. Accessed December 05, 2025.
Last Reviewed: May 9, 2022
Last Updated: May 9, 2022
Chapter Information

For a brief introduction and guide to abbreviations, see Laboratory Tests: General Remarks.

Analyte [material]

Complement, total (CH50), C3, and C4 [S]

Reference range, target level, or decision threshold

CH50 (total complement activity): 90-150 U/mL!!!

C3: 0.55-1.2 g/L!!!

C4: 0.2-0.5 g/L!!!

Interpretation of results

↑ Infections

↓ Congenital complement deficiency, liver diseases, complement consumption (activation by circulating immune complexes), SLE

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