Sarcopenia is currently understood as an organ insufficiency. However, the distinction of acute and chronic sarcopenia as different categories, which makes sense in this conceptual framework, is still evolving. The first set of modern definitions of sarcopenia only considered chronic sarcopenia. However, research showed that function in acute care settings differs from the loss that evolves slowly over months or years, and this fact is starting to permeate modern definitions. The updated version of the EWGSOP definition identifies acute and chronic sarcopenia as subcategories. Different studies have reported rates of incident sarcopenia in hospitalised older patients around 15-20%, which adds to the prevalent sarcopenia present on admission. Diagnosing sarcopenia in acute settings carries specific challenges related to the patients, the acute condition, and limitations in the use of diagnostic tests for muscle mass, muscle strength, and physical performance. Prevention and management of acute sarcopenia rely on exercise during admission, but the quality of evidence is still low. Nutritional intervention and drugs may have a role, but more research is needed.