Studies aiming at improving the treatment of patients on insulin therapy are conducted bidirectionally. On the one hand, there are attempts to find modified insulin that acts even faster and has shorter effect than currently used short-acting insulin analogs, and on the other hand researchers work to develop more stable basal insulins. Fiasp ® is one of the new developments in this field. Addition of two excipients-niacinamide and L-arginine-resulted in faster hypoglycemic effect of insulin aspart while maintaining the stability of drug formulation. Clinical trials assessing pharmacokinetic parameters of Fiasp ® showed a 2 times faster onset of action (4 vs. 9 min), 2 times higher exposure to insulin 30 minutes after its administration and 74% more hypoglycemic activity during the first 30 minutes following subcutaneous injection. Clinical trials of Fiasp ® were conducted under the acronym Onset. Overall, these studies included over 3,000 patients with diabetes, both type 1 and type 2. In patients with type 1 diabetes (DM1) comparable or better diabetes control was observed in the Fiasp ® groups compared with groups treated with Novorapid, with significantly lower blood glucose levels in the early postprandial period. It has also been demonstrated that administration of insulin Fiasp ® within 20 min of the beginning of the meal was associated with comparable results to Novorapid administered before the meal.