Nepal's Prime Minister Girija Prasad Koirala was rushed to a hospital in the Nepalese capital on Monday after he complained of chest pain, officials said.
Home Minister Krishna Sitaula said doctors were examining the 84-year-old politician at the Gangalal Hospital in the capital, Katmandu.
Koirala has been suffering from heart problems, hypertension and asthma.
Sitaula, who was at the hospital, said the prime minister had a busy schedule on Monday, including a lengthy Cabinet meeting. He was scheduled to introduce the government's annual policy in Parliament on Tuesday.
Koirala has tried to avoid a busy schedule since taking office in April after weeks of protests forced King Gyanendra to give up absolute power and reinstate parliament.
He flew to Thailand late last month for a medical checkup, and his doctors announced that his health was improving.