Bal, 42, suffered an attack at his Defence Colony residence and was initially rushed to Aashlok Hospital in Safdarjung Enclave in South Delhi. He was later shifted to Medicity, the source said.
"All his family members are with him in the hospital, " said the source, who is also part of the fashion industry.
Bal, popularly known as 'Gudda' in the fashion industry, has been described as master of fabric and fantasy.
Apart from designing for many Bollywood celebrities, Bal also has international clients like Uma Thurman, Cindy Crawford, Pamela Anderson, Naomi Campbell and Anna Kournikova.
Bal is also brand ambassador of Omega watches since 2001 and has ventured into the hotel business by launching two restaurants - Veda and Cibo - in the capital.