Karrer and Julie Lerch was the son of Paul Karrer, a Swiss dentist who practiced in Russia. In 1892 his family returned back to Switzerland where he studied chemistry inZürich at Alfred Werner and obtained his doctorate in 1911. He got a job with Paul Ehrlich in the Georg Speyer Haus in Frankfurt. In 1919 he became professor in Zurich.
Karrer's former research concerned complex metal compounds but his most important work was on plant pigments, particularly the yellow carotenoids. The formula of carotene was published in 1930. He elucidated their chemical structure in the body were turned into vitamin A. His work led to the correct formula of Beta-carotene; the first time that the structure of a vitamin or provitamin had been established.
George Wald worked briefly in Karrer's lab and studied the role of vitamin A in the retina. Later confirmed Karrer the structure of Ascorbic acid (vitamin C) and extended his research to vitamins B2 (riboflavin) and E (tocopherol). The structures of B2 and E respectively in 1935 1938 were determined. His important contributions to the chemistry of flavines led to the identification of lactoflavine as part of the complex, vitamin B2 originally seemed.
Karrer has more than a thousand articles published in several areas of organic chemistry, in particular on vitamins A, B2, C, E and K, co-enzymes, carotenoids and other plant pigments, amino acids, carbohydrates, curare and other alkoïdes and the organoarseenchemie. His "Lehrbuch der organic chemistry" from 1930 were printed thirteen editions and has been translated in English, Italian, French, Polish and Japanese. Further appeared of his monograph about carotenoids (1948) an English Edition.