Heparin Side Effects Center

Last updated on RxList: 7/19/2022
Heparin Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

What Is Heparin?

Heparin (heparin sodium injectable) is a heterogeneous group of straight-chain anionic mucopolysaccharides, called glycosaminoglycans that have anticoagulant properties used to help prevent clot formation (for example, venous thrombosis, pulmonary embolisms, coagulopathies and coronary artery clots). Heparin is available as generic heparin and under other generic brand names.

What Are Side Effects of Heparin?

Common side effects of Heparin are:

  • easy bleeding and bruising;
  • pain, redness, warmth, irritation, or skin changes where the medicine was injected;
  • itching of your feet; or
  • bluish-colored skin.

Heparin may cause serious side effects including:

  • skin warmth or discoloration,
  • chest pain,
  • irregular heartbeats,
  • shortness of breath,
  • dizziness,
  • anxiety,
  • sweating,
  • unusual bleeding or bruising,
  • severe pain or swelling in your stomach, lower back or growing,
  • dark or blue-colored skin on your hands or feet,
  • nausea,
  • vomiting,
  • loss of appetite,
  • unusual tiredness,
  • bleeding that will not stop,
  • nosebleed,
  • blood in the urine or stool,
  • black or tarry stools,
  • coughing up blood or vomit that looks like coffee grounds,
  • skin changes where the medication was injected,
  • fever,
  • chills,
  • runny nose,
  • watery eyes,
  • easy bruising,
  • purple or red spots under your skin,
  • sudden numbness or weakness,
  • problems with vision or speech,
  • swelling or redness in an arm or leg
  • Thrombocytopenia
  • heparin-induced thrombocytopenia (HIT), and
  • heparin-induced thrombocytopenia and thrombosis (HITT)

Get medical help right away, if you have any of the symptoms listed above.

Seek medical care or call 911 at once if you have the following serious side effects:

  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheartedness, or passing out;
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

Dosage for Heparin

  • Heparin is available in vials at strengths of 1000, 5000, 10,000 and 20,000 units per ml.
  • Dosage depends on the coagulation problem; many initial doses start with 5000 units IV, but this can change depending on the problem; guidelines for dosages are available.
  • If benzyl alcohol is listed as a preservative for the Heparin preparation, do not use in neonates and infants or nursing mothers.
  • If preparations without benzyl alcohol are used in pediatric patients, the initial dose is usually 50 units per Kg but a pediatric specialist should be consulted.

What Drugs, Substances, or Supplements Interact with Heparin?

Heparin may interact with aspirin or other NSAIDs (nonsteroidal anti-inflammatory drugs), other blood thinners, digoxin, dipyridamole, hydroxychloroquine, indomethacin, nicotine (cigarettes, gum, lozenges, or skin patches), nitroglycerin, antibiotics, and cold, allergy, or sleep medications. Tell your doctor all medications and supplements you use.

Heparin During Pregnancy and Breastfeeding

Tell your doctor if you are pregnant or plan to become pregnant while using Heparin. It is unknown if heparin will harm a fetus. Consult your doctor before breastfeeding.

Additional Information

Our Heparin Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer
Heparin Consumer Information

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Get emergency medical help if you have signs of an allergic reaction: nausea, vomiting, sweating, hives, itching, trouble breathing, swelling of your face, lips, tongue, or throat, or feeling like you might pass out.

Heparin may cause you to bleed more easily, which can be severe or life-threatening. You may also have bleeding on the inside of your body. Seek emergency medical attention if you have:

  • skin warmth or discoloration;
  • chest pain, irregular heartbeats;
  • shortness of breath, dizziness, anxiety, sweating;
  • any unusual bleeding or bruising;
  • severe pain or swelling in your stomach, lower back, or groin;
  • dark or blue-colored skin on your hands or feet;
  • nausea, vomiting, loss of appetite;
  • unusual tiredness;
  • any bleeding that will not stop; or
  • nosebleed, blood in your urine or stools, black or tarry stools, or coughing up blood or vomit that looks like coffee grounds.

Heparin can cause you to have bleeding episodes while you are using it and for several weeks after you stop.

Bleeding may be more likely in older adults, especially women over 60 years of age

Stop using heparin and call your doctor at once if you have:

  • skin changes where the medicine was injected;
  • fever, chills, runny nose, or watery eyes;
  • easy bruising, unusual bleeding, purple or red spots under your skin; or
  • signs of a blood clot--sudden numbness or weakness, problems with vision or speech, swelling or redness in an arm or leg.

Common side effects may include:

  • unusual bleeding or bruising;
  • uncontrolled bleeding;
  • allergic reactions; or
  • abnormal liver function tests.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Heart Disease: Symptoms, Signs, and Causes See Slideshow
Heparin Professional Information


The following serious adverse reactions are described elsewhere in the labeling:

  • Heparin-Induced Thrombocytopenia (HIT) and Heparin-Induced Thrombocytopenia and Thrombosis (HITT) [see WARNINGS AND PRECAUTIONS]
  • Thrombocytopenia [see WARNINGS AND PRECAUTIONS]
  • Heparin Resistance [see WARNINGS AND PRECAUTIONS]
  • Hypersensitivity [see WARNINGS AND PRECAUTIONS]

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of heparin sodium. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency.

  • Hemorrhage - Hemorrhage is the chief complication that may result from heparin therapy [see WARNINGS AND PRECAUTIONS]. 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:
    • Adrenal hemorrhage, with resultant acute adrenal insufficiency, has occurred with heparin therapy, including fatal cases.
    • Ovarian (corpus luteum) hemorrhage developed in a number of women of reproductive age receiving short- or long-term anticoagulant therapy.
    • Retroperitoneal hemorrhage.
  • HIT and HITT, including delayed onset cases [see WARNINGS AND PRECAUTIONS].
  • Hypersensitivity - Generalized hypersensitivity reactions have been reported with chills, fever, and urticaria as the most usual manifestations, and asthma, rhinitis, lacrimation, headache, nausea and vomiting, and anaphylactoid reactions, including shock, occurring more rarely. Itching and burning, especially on the plantar side of the feet, may occur [see WARNINGS AND PRECAUTIONS].
  • Elevations of serum aminotransferases - Significant elevations of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels have occurred in patients who have received heparin.
  • Others - Osteoporosis following long-term administration of high-doses of heparin, cutaneous necrosis after systemic administration, suppression of aldosterone synthesis, delayed transient alopecia, priapism, and rebound hyperlipemia on discontinuation of heparin sodium have also been reported.

Read the entire FDA prescribing information for Heparin (Heparin)


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© Heparin Patient Information is supplied by Cerner Multum, Inc. and Heparin Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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