Rights activist Nasrin Sotoudeh began a hunger strike Oct. 17 in protest of prison conditions and the travel ban imposed on her family. She's serving a six-year prison sentence, an imprisonment the United Nations said is arbitrary.
The European Union last month awarded Sotoudeh and film director Jafar Panahi the 2012 Sakharov Prize for Freedom of Thought. Both leaders were jailed for their advocacy campaigns.
European Parliament members in October canceled a trip to Iran after the government there refused to let them meet the jailed dissidents.
Rupert Colville, a spokesman for the U.N. High Commissioner for Human Rights, said the agency was "extremely concerned" about Sotoudeh's health. Colville said that, though Iranian authorities said she's in good health, her visiting husband reports her health has reached the "critical stage."
"The prosecution and imposition of sanctions and other limitations on human rights activists and their family members reflect a disturbing trend apparently aimed at curbing the freedoms of expression, opinion and association," he said in a statement.