Introduction:
Diabetic ketoacidosis (DKA) is an acute complex disorder of carbohydrate, fat, and protein metabolism as well as water-electrolyte and acid-base balance due to sudden and profound insulin deficiency. It is one of the most dangerous complications of diabetes type 1 (T1D).

Aim of the study:
The study aimed to analyse the causes of DKA in patients chronically ill with T1D.

Material and methods:
Records from all 41 hospitalisations (34 patients: 21 females, 13 male; seven hospitalized twice) at the Clinic of Paediatrics, Diabetology, and Endocrinology of the University Clinical Centre in Gdansk in the years 2015–2017 were retrospectively analysed. The average age of the patients was 14 8/12 ±3 years.

Results:
The average duration of diabetes was seven years. In 78% of cases patients were treated with multiple daily dose injections, others with insulin pump. In 44% of cases mild ketoacidosis with pH above 7.2, in 12% moderate, in 34% severe, and in 10% ketoacidosis with pH below 7.0 was diagnosed. Average duration of fluid and intravenous insulin therapy was 30 hours. The most common reasons for ketoacidosis were: self-control errors (98%), omission of insulin doses (78%), and infections (37%). Among patients treated with insulin pump 22% indicated pump failure. In the studied group 34% of patients had psychological disorders; half of them were treated by psychiatrists. In the studied group the average HbA1c level was 11.25 ±2.7%. Previous HbA1c levels were 10.3%, which confirms chronically inappropriate metabolic control in the analysed group. Most of the patients regularly visited a diabetes outpatient clinic, 27% irregularly, and 5% did not apply for control visit during the previous years.

Conclusions:
Self-control errors leading to chronic hyperglycaemias, irregular visits to a diabetology outpatient clinic, and breaks in insulin therapy were the most common causes of ketoacidosis in patients with long-term type 1 diabetes. Most of the patients were teenagers a few years after diagnosis of diabetes with coincidence of psychological and psychiatric disorders.