Difference Between LMWH and Heparin

LMWH and Heparin are both anticoagulants. Coagulation means forming blood clots to prevent blood loss due to excessive bleeding. When coagulation occurs in undesired situations and places inside our bodies (thrombosis) it is very dangerous because it can alter or reduce blood supply to organs and even be fatal. This happens when soluble protein fibrinogen is converted to fibrin, a non-soluble form, and it forms clots with platelets. Anticoagulants are used to inhibit this process in high risk situations like a long time immobilization and surgery.


LMWH – Low Molecular Weight Heparin as the name implies is a group of heparins with low molecular weights. This is not how heparin naturally occurs in our bodies. LMWH is made by extracting the heparin and then fractionating it by methods like oxidative depolymerisation, alkaline beta-eliminative cleavage, deaminative cleavage etc.

By definition LMWH consists of heparin salts/polysaccharide chains with average weight of 8000 Da. Atleast, 60% of the heparin molecules in LMWH are weighing less than 8000Da. Some LMWH heparins available in the market are Bemiparin, Certoparin, Dalteparin etc. Anticoagulant effect is high in LMWH. It is given as a subcutaneous injection. The mechanism of action is to bind to Antithrombin and increase inhibition of thrombin that perform coagulation and an anti-factor called Xa. Examining the effects of LMWH is done by anti-factor Xa activity measurements. If LMWH is given to a patient of extreme weights (high/low) or a patient with renal dysfunction, careful monitoring is a must.


Heparin also referred to as unfractionated heparin is made up of polysaccharide chains. Their weights range from 5000 Da to more than 40000 Da. This is how heparin naturally occurs in our bodies. For medicinal usage heparin is extracted from bovine lung or porcine intestines. It is given as an intravenous injection in a high dose than LMWH.

Heparin should not be used if one is allergic or have high blood pressure, bacterial infection in the heart lining, hemophilia, liver disease, any bleeding disorder, or even menstrual period. The same applies to LMWH. There can be side effects like numbness, difficulty in breathing, chest pain, chills, bluish skin, redness in legs and many more when taking heparin or LMWH. But side effects are high in heparin than LMWH. Certain drugs like aspirin, ibuprofen or non-steroidal anti-inflammatory drugs should not be used while taking heparin or LMWH because they tend to increase bleeding.

LMWH vs Heparin

• LMWH polysaccharide chains have a low molecular weight than heparin.

• LMWH is made by fractionating heparin, but heparin is used as it is after extraction.

• LMWH is given as a subcutaneous injection, but heparin is given as an intravenous injection and in high dose.

• Activity of LMWH is done by monitoring anti-factor Xa activity, but heparin activity is monitored by APTT coagulation parameter.

• The risk of bleeding is low in LMWH than it is in heparin.

• LMWH has low risk of osteoporosis than heparin when used for a long time.

• LMWH has fewer side effects than heparin.