The management of pregestational diabetes requires tight metabolic control to reduce maternal and perinatal morbidity and mortality. It has been suggested that type I diabetes is a disorder characterized by insulin deficiency and type II diabetes is characterized by insulin resistance; however, it may be hypothesized that a difference in insulin requirements should emerge throughout pregnancy to reflect the dissimilarities in these two metabolic disturbances. The current investigation of 103 women with pregestational diabetes used a novel approach (reflectance meters with onboard memories) to uncover the actual insulin dosages required to reach and maintain optimum metabolic control throughout pregnancy. It was found that both type I and type II diabetes appear to have a triphasic insulin pattern, with the patient having type II diabetes requiring significantly higher doses of insulin during each trimester. This seems to suggest that the hormonal changes in pregnancy may have a similar effect on both type I and type II diabetes but to a different degree. Thus this should be considered in the treatment of pregestational diabetes and in the development of an algorithm for diabetes management.