The syndrome of inappropriate antidiuresis (SIAD) is a rare and significant side effect of a variety of medications such as antidepressants, chemotherapeutic medications, and non-steroidal anti-inflammatory drugs. Regarding dipyrone, only a few cases have been mentioned in the world. The non-opioid analgesic metamizole (dipyrone) is used for the treatment of acute or chronic pain and fever and is one of the most frequently prescribed over-the-counter medications in Israel, Brazil, and Mexico. Dipyrone has low anti-inflammatory properties yet inhibits prostaglandins to some degree. In this case report, we present a case of a post-operative patient, who was on an analgesic cocktail containing dipyrone. The patient developed a new and sudden hyponatremia, namely, a drop of 12 meq/L of sodium in less than 24 hours. Dipyrone was found to be the culprit drug. Our case report demonstrates the importance of considering dipyrone in the diagnosis of medication-induced SIAD in patients taking analgesics.