L-Penicillamine is primarily used in medicine for the treatment of Wilson's disease, a genetic disorder that causes copper to accumulate in the body. It works by binding to excess copper and facilitating its excretion through urine, thereby preventing damage to the liver, brain, and other organs.

Additionally, it is employed in the management of rheumatoid arthritis, particularly in cases where other treatments have not been effective. It helps reduce inflammation and slow the progression of joint damage by modulating the immune response.

In rare cases, L-Penicillamine is also used to treat cystinuria, a condition that leads to the formation of cystine stones in the kidneys. It helps by forming a soluble complex with cystine, reducing the risk of stone formation.

Due to its potential side effects, such as bone marrow suppression and kidney damage, its use is carefully monitored, and it is typically prescribed when the benefits outweigh the risks.