Dalteparin is used in combination with aspirin to prevent serious or life-threatening complications from angina (chest pain) and heart attacks. Dalteparin is also used to prevent deep vein thrombosis (DVT; a blood clot, usually in the leg), which can lead to pulmonary embolism (PE; a blood clot in the lung), in people who are on bedrest or who are having hip replacement or abdominal surgery. It is also used treat DVT or PE and prevent it from happening again in children one month of age and older, and in adults with DVT or PE who have cancer.