In 1955, she became uncomfortable with her weight and started using a slimming medication given by her mother. She used the medication regularly and managed to return to her previous shape until the early 1960s. In 1967, she started using a slimming medication called 'Pat.' She was unaware of the presence of the Amphetamine substance in the medication. Amphetamine is a nerve system-disrupting drug. Özdemir Birsel's busy work schedule overwhelmed Belgin Doruk. She sought solace in alcohol and later received an offer for singing. Under the influence of the medication, she felt like an opera singer and accepted the offer. She ignored Zeki Müren's suggestion to take music lessons. Under the influence of Amphetamine, she lost touch with reality. On her first night on stage, she started reciting poetry instead of singing. The audience and backstage were astonished by the incident. Belgin Doruk's first stage experience ended in failure, and she opened her eyes in her bed.[13] She trembled all over, and around this time, Özdemir Birsel faced financial difficulties. Belgin Doruk was admitted to the French Lape Hospital in Şişli after suffering a nervous breakdown. The iron doors of the hospital, where mental patients were treated, terrified Belgin Doruk. The room she was confined in seemed like a prison to her, and her screams echoed from the locked room. There were even claims that she was chained. Özdemir Birsel went bankrupt in the early 1970s. Economic turmoil was added to Belgin Doruk's loneliness and unhappiness. After facing these difficulties and gaining weight, she appeared in her last film in 1972 and announced that she was retiring from acting in 1975. After quitting acting for 20 years, she fell ill one night in Bebek. On her last night, her blood pressure kept fluctuating. In the early hours of March 27, 1995, she passed away. Her funeral was held at Şişli Mosque, and she was laid to rest at Zincirlikuyu Cemetery.