What the label lists and what reports show
Heparin side effects
Heparin's FDA label: “Hemorrhage is the chief complication that may result from heparin therapy (see WARNINGS ).” FAERS holds 13,673 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is heparin-induced thrombocytopenia (1,273 reports).
- Generic listed
- In shortage
Check it at the source: the heparin FDA label on DailyMed (effective November 28, 2025, Fresenius Kabi USA, LLC); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsHemorrhage is the chief complication that may result from heparin therapy (see WARNINGS ).
From the label: adverse reactions, continuedHemorrhage Hemorrhage is the chief complication that may result from heparin therapy (see WARNINGS ). An overly prolonged clotting time or minor bleeding during therapy can usually be controlled by withdrawing the drug (see OVERDOSAGE ). It should be appreciated that gastrointestinal or urinary tract bleeding during anticoagulant therapy may indicate the presence of an underlying occult lesion. Bleeding can occur at any site but certain specific hemorrhagic complications may be difficult to detect: (a) Adrenal hemorrhage, with resultant acute adrenal insufficiency, has occurred during anticoagulant therapy. Therefore, such treatment should be discontinued in patients who develop signs and symptoms of acute adrenal hemorrhage and insufficiency. Initiation of corrective therapy should not depend on laboratory confirmation of the diagnosis, since any delay in an acute situation may result in the patient’s death. (b) Ovarian (corpus luteum) hemorrhage developed in a number of women of reproductive age receiving short- or long-term anticoagulant therapy. This complication, if unrecognized, may be fatal. (c) Retroperitoneal hemorrhage. Thrombocytopenia, Heparin-induced Thrombocytopenia (HIT) and Heparin-induced Thrombocytopenia and Thrombosis (HITT) and Delayed Onset of HIT and HITT See WARNINGS . …
Source: FDA drug label, Fresenius Kabi USA, LLC, effective November 28, 2025 (SPL set d55b4a63-0c04-4874-b74f-9e9b9e8b008c), via openFDA; the full label on DailyMed
What do FAERS reports show?
13,673 reports list heparin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2,609 are coded as a death and 5,454 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 19 reactions below, 6 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Heparin: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions