This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
During treatment for Wilson disease with trientine and penicillamine, free serum copper should be kept below which level? 
Select and explain. 
A. 25 mcg/dl, B. 50 mcg/dl, C. 75 mcg/dl, D. 100 mcg/dl
A: 25 mcg/dl
Answer: A: 25 mcg/dl 
Explanation: The normal free copper value is 10-15 mcg/dL and it is often as high as 50 mcg/dL in untreated Wilson's disease. With treatment, free copper should be <25 mcg/dL. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 3190