Severe poisoning with potassium pills is rare but patients may present with serious cardiovascular symptoms requiring immediate and effective treatment. A 30-year-old healthy woman presented to the emergency department after ingestion of 300 slow-release pills of potassium-chloride with serum potassium of 9.5 mmol/l, and poor cardiovascular function. Gastric lavage was performed with poor outcome. Despite intensive medical treatment serum potassium remained very high around 9 mmol/l. Haemodialysis was initiated but despite ongoing dialysis, potassium increased to 10.3 mmol/l. Hence, a parallel dialysis was started and after 4 h of parallel dialysis, serum potassium decreased to 6.4 mmol/l. An x-ray revealed large amounts of pills remaining in the stomach and the surgeon was able to remove about 200 pills through an acute laparotomy. The patient recovered slowly thereafter, but later developed a gastric stricture and pulmonary embolism.