ultralente insulin ultralente insulin ultralente insulin was a long-acting form of insulin. it has an onset of 4 to 6 hours, a peak of 14 to 24 hours, and a duration of 28 to 36 hours. ultralente insulin, along with lente insulin, were discontinued in the us by manufacturers in the mid-2000s. one of the reasons for discontinuation was declining use in favor of nph insulin and other newer insulin products. the fda withdrew approval for ultralente insulin products by 2011. history