Academician Željko Reiner was born in Zagreb in 1953, where he attended a Zagreb elementary school, and then the Classical Gymnasium. He graduated from the School of Medicine in 1976, in 1978 he received his MSc degree, and in 1982 PhD at the University of Zagreb. From 1979 to 1983 he specialized internal medicine at the Sisters of Mercy University Hospital Centre in Zagreb, and at the University Medical Center Hamburg-Eppendorf in Germany. He was a postdoctoral researcher in Oklahoma City USA from 1984 to 1985.
In 1986 he was appointed associate professor at the School of Medicine, University of Zagreb, and in 1988 full professor. From 1997 he is full professor of internal medicine with tenure, and from 2009 full professor at the University of Rijeka. He is Fellow of the Royal Society of Physicians – FRCP (London), Fellow of the European Society of Cardiology – FESC, and Fellow of the American College of Cardiology – FACC. From 1986 to 1995 he was head of the of Clinical research division, Department of pathophysiology, University Hospital Centre Zagreb, from 1995 to 2003, and from 2011 to 2015 head of the Department of internal medicine, University Hospital Centre Zagreb. Since 2003 he has been head of the Division for metabolic diseases, University Hospital Centre Zagreb. From 2004 to 2012 he was director of the University Hospital Centre Zagreb. During his tenure our biggest hospital was expanded and received modern equipment, and is now one and a half times the size it was before he stepped in.
He has been a member of the Croatian Academy of Medical Sciences since 1990, and from 2004 to 2012 he was the Academy’s president. From 1992 to 2006 he was a member-associate of the Croatian Academy of Sciences and Arts, and from 2006 regular member and academician. In 2011 he was named an honorary member of the Academy of Medical Sciences of Bosnia and Herzegovina. From 2000 to 2006 he was chairman of the Department of internal medicine at the School of Medicine, University of Zagreb.
He published 563 scientific and professional papers, and according to Google data base he has over 65,000 citations. He was a visiting professor at several universities in the USA and Europe, invited speaker at a number of European and world conferences, member of scientific committees of almost all European and world congresses on atherosclerosis in the past 20 years, European and world cardiology congresses, and he organized and presided several local congresses. Since 1983 until today he has been the leader of several scientific research projects. He is a member of the editorial boards of several most distinguished international journals (Journal of the American College of Cardiology–JACC, Nature-Reviews Cardiology, Atherosclerosis, Nutrition, Metabolism & Cardiovascular Diseases, and other), and of local journals (Journal of the Croatian Medical Association, and other). He also reviews world’s most famous scientific journals (The Lancet, European Heart Journal, Circulation Research, Annals of Medicine, Fundamental and Clinical Pharmacology, European Journal of Preventive Cardiology, Cardiovascular Drugs and Therapy, and other).
In the European Atherosclerosis Society Executive Committee he was the counsellor for national societies for atherosclerosis, he was member of the Board of the European Association for Cardiovascular Prevention and Rehabilitation (EACPR), chairman of the EACPR Committee for science and guidelines, and member of two most important committees – Committee for practice guidelines and Congress committee ESC.
He is also the founder and longtime president of the Croatian Society for Atherosclerosis, the founder of the Croatian Society of Hypertension, founder and ex-vice president of the Croatian Society for Obesity. He was member of the Committee for election of ESC fellows, and secretary general of the Croatian Medical Association. He is one of the founders of the Catholic University of Croatia in 1991.
He was the first Croat who was the main author of some key European guidelines – European guidelines for the treatment of dyslipidaemia published in 2011, and co-author of the second edition of these guidelines in 2016. He is a co-author of the European guidelines for cardiovascular disease prevention issued in 2007 and 2012. From 1992 to 2000 he was chairman of the Croatian committee for drugs (member of the committee from 2004 to 2008), and president of the Committee for naming head doctors (1998-2000). He was also the president of the European committee for the fight against smoking (2000 – 2002). He was a member of the International committee for one of the most significant world medical awards Léon Bernard Foundation Prize.

From 1995 to 1998 he was a member of the Executive board of the World Health Organization, and was the second Croat to serve as such. From 2012 to 2016 he was one of only six members of the Board of the International Atherosclerosis Society – IAS where he represented the entire Europe.
He was the expert of the European Commission for the evaluation of scientific project proposals received under the FP6 and FP7 for funding in the European Union .
He is the author of chapters in 30 books and textbooks published in Croatia and abroad, and was the head of several courses at undergraduate and seven postgraduate studies. He was the editor of 28 books and manuals (Pharmacotherapy Handbook, Internal Medicine, and other). From 2010 to 2018 he was a member of the Council of the University of Zagreb.
He was a volunteer in the Croatian War of Independence from the early days of its onset as a member of the medical headquarters, initially the first deputy commander in charge of education and training, and later for the medical personnel.
He has been honored with the following civilian and military awards: Order of Duke Trpimir, Order of Ban Jelačić, Order of Danica Hrvatska, Order of the Croatian Trefoil, Order of the Croatian Interlace, Homeland War Memorial Medal, Medal for Participation in Operation “Flash”, Medal for Participation in Operation “Storm”, Medal for Participation in Operation “Summer ’95” and Memorial Medal “Vukovar”. In 2007 he was named honorary citizen of Korčula. He was awarded with the “Ladislav Rakovac Award” and “City of Zagreb Award” in 2010.
From 1993 to 1998 he was deputy of the Minister of Health , and from 1998 to 2000 Minister of Health of the Republic of Croatia. From 2010 to 2015 he was president of the Croatian National Health Council.
In 2008 he was elected member of the Board of Health and Welfare at the Croatian Parliament. From 2011 to 2012 he was vice-president of the Committee for Science, Education and Culture at the Croatian Parliament (currently a member of this Committee). In Parliament he was also a member of the Board for the Interparliamentary Cooperation and deputy member of the delegation in the Parliamentary Dimension of the Central European Initiative.
From 2012 to 2016 he was vice-president, from 2016 to 2017 president, and since 2017 again vice-president of the Croatian Parliament, but he is still active at the School of Medicine and the University Hospital Centre Zagreb.