The diagnosis "leukemia" Westerwelle delivered in 2014 — six months after his resignation from the post of head of the German Foreign Ministry. In November 2015, the politician presented the book "Between two lives" and appeared on television, where he spoke about his fight with cancer.

Then a number of German media expressed the hope that Westerwelle has managed to beat the disease, but in December 2015, he again was hospitalized. As the official reasons for hospitalization has been named the new medication after bone marrow transplantation. In the hospital Westerwelle remained until his death.

Since the late 1980s, Guido Westerwelle played a prominent role in German politics. As a member of the Free democratic party (FDP) and for a long time while in opposition in 2009, he became Minister of foreign Affairs of Germany after the free Democrats together with the CDU/CSU won the elections to the Bundestag. In this position, Westerwelle remained until 2013.