Serum copper levels or serum ceruloplasmin are useful tests for detecting copper deficiency.
Copper is a component of many body proteins; almost all of the body's copper is bound within copper proteins. Unbound (free) copper ions are toxic. About half of ingested copper is absorbed by the body. Excess copper is excreted through bile.
Serum copper may be elevated with infection, inflammation, stress, copper supplementation, oral contraceptives, and pregnancy. Concentrations are 2-3 times normal in the third trimester of pregnancy. Copper may be lowered with corticosteroids, zinc, malnutrition, and malabsorption.
Elevated results from noncertified trace element-free tubes may be due to contamination. Elevated concentrations of trace elements in serum should be confirmed with a second specimen collected in a trace element-free tube, such as royal blue sterile tube (no additive).
A low ceruloplasmin level usually means that total serum copper is low. However, the free (unbound) copper level is usually increased. Free copper can be calculated by subtracting the amount of copper in ceruloplasmin from total serum copper, or it can be measured directly.
In cases of autoimmune disease, where therapy is often less than satisfactory, copper insufficiency should be investigated until additional studies confirm any link. The following quote is by John Johnson (iThyroid.com):
"There is very little scientific evidence that copper is involved in immune system function, but it is my belief that copper deficiency is the principal nutritional deficiency involved in autoimmune diseases. Approximately 80% of the people who suffer from autoimmune diseases are women. The most important nutrient that women need more of than men is copper. Any nutritional detective who is trying to find the culprit in autoimmune diseases should first suspect copper. Women need more copper and get autoimmune diseases more frequently. Men need less copper and generally don't get autoimmune disease. Copper deficiency is the obvious suspect."
Melanin, the normal body pigment, is synthesized from the essential amino acid L-phenylalanine by an enzyme system dependent on copper, vitamin B6, vitamin C. That's why these nutrients are all part of vitiligo repigmentation programs, also.
Although 4mg of copper sebacate daily is usually a safe minimum amount, it is best to have red cell copper levels tested before settling on an amount of copper for long term treatment.
Testing serum or hair copper levels is usually adequate for evaluating copper status when low levels of copper are suspected and hair contamination with copper can be ruled out. When in doubt, it would be better to use more accurate tests such as the 24 hour urine copper or serum ceruloplasmin.