Abstract Background and Aims Hyponatremia (<135mEq/L) is the most common electrolyte disorder observed in clinical practice, associated with increased hospital admissions and mortality. One of its causes is the syndrome of inappropriate antidiuretic hormone secretion (SIADH). In chronic SIADH, urea is considered as a therapeutic possibility among other measures; however, its use is not widespread due to few studies on its efficacy. Objects To evaluate sodium levels in patients with chronic SIADH who received oral urea for at least 12 months. Method Observational, descriptive and retrospective study. Population: 13 patients with SIADH under treatment with urea for 12 months. The relationship between natremia and the rest of the clinical variables was analyzed using Chi-square, Student's T test, and ANOVA or their corresponding non-parametric tests. Results Mean age: 64 years +/-15. Men: 61% (n = 8). Comorbidities: hypertension (50%, n = 6), CKD (30.7%, n = 4), diabetes (15.3%, n = 2). SIADH etiology: Antiepileptics (n = 4), idiopathic (n = 3), intracranial pathologies (n = 5) and cancer (n = 1). 61% required admission for SIADH. Median of 10 ± 26 months from diagnosis to start of treatment. The initial dose was: 15 grams/day (53%, n = 7), 15 grams every 48 hours (30%, n = 4) and 15 grams every 72-96 hours (17%, n = 2). At one year, 61% of patients maintained the same dose (n = 8) and 39% of patients required an increase in the dose (n = 5) and of these 3 patients they increased to 30 grams/day. The treatment was well tolerated, only 1 patient out of 13 (7.6%) reported nausea and dysgeusia, no patient presented hypernatremia (Na >145meq/L), hospital admissions due to SIADH, or adverse effects that led them to discontinue urea. Conclusion After a year of treatment, urea increases and maintains plasma sodium in the normal range safely in chronic SIADH. Treatment with urea is well tolerated, avoids hospitalizations, and is not associated with complications from its use.