Protein Supplementation in Hyponatremia Due to the Syndrome of Inappropriate Antidiuresis

Who May Qualify: - Adult patients with confirmed SIAD during the hospital stay or at screening, defined by: - Plasma sodium concentration \<135 mmol/L - Plasma osmolality \<300 mOsm/kg - Urine osmolality \>100 mOsm/kg - Urine sodium concentration \>30 mmol/L - Clinical euvolemia (no signs of hypovolemia or hypervolemia) Who Should NOT Join This Trial: - Lactose intolerance, milk protein allergy, soy allergy, nuts allergy, or hypersensitivity to components of the protein supplement. - Inborn metabolic disorders affecting carbohydrate, lipid, or protein metabolism. - Severe symptomatic hyponatremia requiring 3% NaCl or intensive care. - New (within the last five days) treatment with SGLT2 inhibitors, vaptans or oral urea - Uncontrolled severe hypothyroidism (untreated) - Uncontrolled adrenal insufficiency (morning cortisol \<150nmol/l) - eGFR \<45 mL/min/1.73 m² (KDIGO G3b-5) or end-stage renal disease (dialysis) - Severe hepatic impairment or advanced symptomatic liver disease defined as past or current hepatic encephalopathy, liver cirrhosis Child C, or decompensated (bleeding, jaundice, hepatorenal syndrome) - Pregnancy, breastfeeding, or plans to become pregnant during the study. - End-of-life care - Lack of capacity or other reasons preventing from giving willing to sign a consent form or following study procedures (e.g., due to language problems, psychological disorders, dementia, etc.) - Treatment with thiazid diuretic (must be stopped at least 48 hours before inclusion) Post-randomization Who Should NOT Join This Trial: - Type 1 diabetes or uncontrolled type 2 diabetes (HbA1c \>8.0%) Always talk to your doctor about whether this trial is right for you.