Ceruloplasmin binds some of the copper circulating in the peripheral blood. The amount of copper that is not bound (assuming normal ceruloplasmin binding) can be estimated from the serum copper and ceruloplasmin levels. This is termed the "copper index" by some.


Molecular Weight of Copper (Cu): 63.54 grams


copper not bound to ceruloplasmin in µg/dL =

= (total serum copper in µg/dL) – (3 * (serum ceruloplasmin in mg/dL))


copper not bound to ceruloplasmin in µmol/L =

= (total serum copper in µmol/L) – (0.047 * (serum ceruloplasmin mg/L))



• 3 is in µg copper bound per mg ceruloplasmin

• 0.047 is µmol copper bound per mg ceruloplasmin

• To convert µg/dL to µmol/L, multiply by 10 / 63.54 = 0.1574



• The normal nonbound serum copper is 0 – 10 µg/dL.

• Toxic levels of copper are associated with increased nonbound serum copper.

• In Wilson's disease, the amount of nonbound serum copper is increased.



• The blood samples need to be collected correctly in a plastic vial or metal free tube to prevent falsely elevated serum values.


NOTE: According to Tietz NW, Clinical Guide to Laboratory Tests, Third Edition, 1995, page 168, normal plasma copper is about 80% of the serum levels for males and 90% of the serum levels for females.


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