Hypercalcemia is in many cases a symptom of advanced stage malignant diseases due to increased resorption and reduced secretion. A slightly increased hypercalcemia is mostly asymptomatic but high calcium levels are associated with neurological, gastrointestinal, cardiac and renal symptoms. Important diagnostic tools are the determination of serum albumin and ionized calcium levels. Therapeutic intervention depends on the clinical symptoms as well as calcium levels. Furthermore, increase over time and duration of hypercalcemia has to be taken into account. The principles of treatment are sufficient fluid replacement and maintaining adequate diuresis. In addition, calcitonin, bisphosphonates and steroids are effective and widely used to decrease plasma calcium levels.