Since his early years of school, he displayed a remarkable intelligence, learning French, Latin and Greek and a few years later he spoke fluently these languages and read classical works of Latin and Greek literature in the original. He also had a particular talent for drawing and music and special inclinations to natural and physicochemical sciences.
He left for Paris in the autumn of 1888, where he entered the Faculty of Medicine. In 1897 he obtained the title of Doctor of Medicine and, at the same time, the rank of deputy surgeon general of the Notre Dame du Perpetuel-Secours Hospital.
In 1900, Paulescu returned to Romania, where he remained until his death (1931) as Head of the Physiology Department at the Faculty of Medicine and also Professor of Clinical Medicine at the Hospital St. Vincent de Paul in Bucharest.
In 1916, Paulescu obtained an aqueous pancreatic extract which, injected into a diabetic dog, proved efficacious. After a gap caused by World War I, he resumed his research and succeded in isolating the antidiabetic pancreatic hormone ("Pancreine").
From April 24 to June 23, 1921, Paulescu published four papers at the Romanian Section of the Society of Biology in Paris:
He also patented the process of manufacturing the pancreine (his name of insulin) with patent no. 6254 of April 10, 1922 at the Minister of Industry and Trade in Romania.
Eight months after the publishing of Paulescu's works, doctor Frederick Grant Banting and biochemist John James Richard Macleod from Canada, working at the University of Toronto, announced their results about the hyperglycemia of diabetic dogs, using a pancreatic extract. Their conclusion was that Paulescu's paper was correct, being simply a confirming paper, with direct references to that article.
In the next year, to everyone's surprise, they receive the 1923 Nobel Prize in Physiology or Medicine.
The merits of Nicolae Paulescu, as being the first to discover the insulin, were recognized only after 50 years from the first patent of procedure to produce insulin.
He was criticised for expressing his anti-semitic and anti-masonic views in some articles like "The judeo-masonic plot against the Romanian nation".
On August 27 2003, at the Hôtel-Dieu State Hospital of Paris, the inauguration of the buste of professor Paulescu was canceled after the protest of several jewish protection associations: