The insulin used in insulin pumps and regular insulin, despite their similar names, have different uses and drug concentrations, which can directly endanger the safety of patients if they are confused. Therefore, both patients, family members and doctors should be extra careful. Case presentation: The patient, female, 13 years old, with type 1 diabetes for 8 years, was hospitalized 3 months ago due to poor glycemic control and switched to subcutaneous insulin pump for blood glucose control. After monitoring blood glucose and adjusting the basal rate and preprandial amount of insulin pumped in, she was discharged with smooth blood glucose control and total daily insulin amount of 36.8 IU at the time of discharge. she did not bring additional medication because she had just loaded new insulin into the insulin pump before discharge. However, two weeks later, the patient went to the emergency room with severe nausea and vomiting, and was diagnosed with “diabetic ketoacidosis” after a positive urine ketone body and acidic blood gas. The patient’s nausea and vomiting gradually subsided, and he could eat liquid food in the next morning, and the urine ketone body was negative on recheck. The subcutaneous insulin pump used by the patient was examined and worked completely normally. After detailed questioning of medical history, we learned that the patient’s parents were abroad and the patient lived with his grandparents for a long time, and his grandfather was responsible for medical issues such as medication collection. The insulin pump had been working normally after the previous discharge, and the insulin was replaced 5 days ago because it had run out of insulin. The patient’s grandfather was asked to find out the packaging of the insulin after the replacement and found that it was a bottle of Novolin R (400IU/pc). So the residual insulin in the pump was discarded and replaced with insulin in the refill of Novolin R. The blood glucose control was stable and he was discharged from the hospital soon. Case analysis: This is a problem caused by the lack of meticulousness in prescribing medication at the outpatient clinic. The insulins used in the insulin pump are all short-acting insulins and are set to the refill used in the pen syringe. Although the bottled Novolin R and Novolin R refills are both genetically recombinant short-acting human insulin, they are not only different in dose, but also in concentration, with the Novolin R refill being much more concentrated. Thus, even if the same dose of bottled Novolin R is pumped, the amount of insulin pumped by the insulin pump throughout the day is more than 50% lower than the original, and blood sugar control is naturally not satisfactory. The invention of insulin pump is a boon to type 1 diabetic patients, but it is also a double-edged sword. Due to the absolute lack of insulin, the blood glucose of type 1 diabetic patients fluctuates greatly, and after using insulin pump, the blood glucose fluctuation will be controlled within an acceptable range. However, the insulin pump is a complicated instrument, and if something goes wrong, the supply of insulin is often interrupted, which can easily increase the risk of ketoacidosis for type 1 diabetic patients. For patients, the use of insulin pumps must be very careful, if there is not quite understand the place do not take for granted, as much as possible to consult the doctor. In the case of the patient’s grandfather, he could not tell what kind of insulin he was using when he went to the hospital to prescribe it, and he did not bring the outer packaging, which ultimately resulted in a “mistake of a thousand miles”. The habit of meticulousness is even more important for doctors. If the special features of insulin use by insulin pump had been emphasized during hospitalization, and if the outpatient doctor had insisted on prescribing the drug after confirming the treatment plan, the patient might not have developed ketoacidosis this time. Of course, if a problem arises, it is important to take a meticulous medical history and find out the root cause in order to avoid the same mistake from happening again.