This was set by James Collip at the University of Toronto in 1922. Of course, this was dependent on the size and diet of the rabbits. The unit of insulin was set by the insulin committee at the University of Toronto. The unit evolved eventually to the old USP insulin unit, where one unit (U) of insulin was set equal to the amount of insulin required to reduce the concentration of blood glucose in a fasting rabbit to 45 m g/d l (2.5 m mol/L). Once the chemical structure and mass of insulin was known, the unit of insulin was defined by the mass of pure crystalline insulin required to obtain the USP unit. The unit of measurement used in insulin therapy is not part of the International System of Units (abbreviated SI) which is the modern form of the metric system. Instead the pharmacological international unit (IU) is defined by the WHO Expert Committee on Biological Standardization. Potential complications
The central problem for those requiring external insulin is picking the right dose of insulin and the right timing. Physiological regulation of blood glucose, as in the non-diabetic, would be best. Increased blood glucose levels after a meal is a stimulus for prompt release of insulin from the pancreas. The increased insulin level causes glucose absorption and storage in cells, reduces glycogen to glucose conversion, reducing blood glucose levels, and so reducing insulin release.
had used
1923 Farbwerke Hoechst, one of the forerunners of todays Sanofi Aventis, produces commercial quantities of bovine insulin in Germany
1923 Hans Christian Hagedorn founds the Nordisk Insulinlaboratorium in Denmark – forerunner of todays Novo Nordisk
1923 Constance Collier returns to health after being successfully treated with insulin in Strasbourg
1926 Nordisk receives a Danish charter to produce insulin as a non-profit
1936 Canadians David M. Scott and Albert M. Fisher formulate a zinc insulin mixture at Connaught Laboratories in Toronto and license it to Novo
1936 Hagedorn discovers that adding protamine to insulin prolongs the duration of action of insulin
1946 Nordisk formulates Isophane porcine insulin aka Neutral Protamine Hagedorn or NPH insulin
1946 Nordisk crystallizes a protamine and insulin mixture
1950 Nordisk markets NPH insulin
1953 Novo formulates Lente porcine and bovine insulins by adding zinc for longer lasting insulin
1955 Frederick Sanger determines the amino acid sequence of insulin
1965 Synthesized by total synthesis by Wang Yinglai, Chen-Lu Tsou, et al. 1969 Dorothy Crowfoot Hodgkin solves the crystal structure of insulin by X-ray crystallography
1973 Purified monocomponent (MC) insulin is introduced
1973 The U.S. officially "standardized" insulin sold for human use in the U.S. to U-100 (100 units per milliliter). Prior to that, insulin was sold in different strengths, including U-80 (80 units per milliliter) and U-40 formulations (40 units per milliliter), so the effort to "standardize" the potency aimed to reduce dosage errors and ease doctors job of prescribing insulin for people. Other countries also followed suit.