Peptide receptor radionuclide therapy is routinely used for neuroendocrine tumors. To prevent radiopeptide retention at the proximal tubule of the kidney, positively charged amino are coinfused. However, hyperkalemia (>5.0 mmol/L) in more than three fourth of patients has been reported. In our case, the patient experienced acute hyperkalemia with blood values greater than 7.0 mmol/L with gastroparesis and subileus.