Ringer lactate, also known as Lactated Ringer's Solution (LR) or Hartmann's solution, is an intravenous fluid containing water, sodium, potassium, calcium, and lactate to replenish fluids and electrolytes in cases of dehydration, trauma, blood loss, and during surgery. It is an isotonic, balanced solution that helps restore fluid balance and is preferred over normal saline in some situations to avoid hyperchloremic metabolic acidosis.