Insulin isophane is a recombinant human insulin analogue (genetically modified insulin that is grown in a laboratory and similar to human insulin). It is an intermediate acting insulin preparation. Insulin isophane acts by replacing the normal production of insulin and by helping transfer sugar from the blood into other body tissues where it is utilized to generate energy. It also stops the liver from producing more sugar. Intermediate acting insulin preparations start acting within an hour or 2 of injection, and reach a period of peak activity that lasts up to 7 hours, following which the action trails off; overall duration of action ranges from 18 to 24 hours.