What is the most common side effect of heparin?

The most common side effect of heparin is hemorrhage, which refers to excessive bleeding. Heparin is an anticoagulant, meaning it works by inhibiting the blood's ability to clot, which is its primary therapeutic function. However, this mechanism also predisposes patients to bleeding complications, particularly if the heparin dosage is not carefully monitored or if the patient has other risk factors for bleeding.

Patients on heparin therapy are typically assessed for signs of bleeding, such as unusual bruising, blood in urine or stools, and prolonged bleeding from cuts. The risk of hemorrhage is a significant concern in clinical settings, especially during surgical procedures or in patients with existing bleeding disorders.

Other side effects listed, such as hypersensitivity, thrombosis, and hypokalemia, can occur with heparin, but they are not as common as hemorrhage. Hypersensitivity reactions might happen in a small number of patients, thrombosis can actually occur if the anticoagulation isn't sufficient, and hypokalemia may occur due to other causes but is not a primary effect of heparin usage. Thus, bleeding is recognized as the most frequent adverse effect associated with heparin therapy.