Lovenox: What You Should Know After Surgery

Understand the risks and side effects of blood thinners

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Lovenox, also known as enoxaparin, is a prescription blood thinner. It is used to reduce the ability of the blood to clot in individuals who have issues with blood clotting, and in hospitalized patients who are at an increased risk of forming a blood clot. Surgery patients are known to be at a higher risk of forming blood clots after surgery, so that patient population is even more likely to need a medication to prevent blood clots.

Close up of person drawing blood from another person's arm
 Franz Aberham / Getty Images 


Lovenox is primarily used to prevent blood clots. One of the things that blood does well is clot. This prevents us from bleeding to death when we have an injury or incision. If our blood did not clot, we would be unable to survive even the smallest of injuries, such as a paper cut. It is the ability of blood to clot that prevents us from having a massive hemorrhage when we accidentally cut our finger when cooking, or when we have a surgical procedure.

The ability to clot is very important, but sometimes the blood is too likely to clot. After surgery, there is an increased risk of a problem called Deep Vein Thrombosis, or DVT. This is where clots form in the extremities, usually the legs. The period of inactivity during surgery, and often during the hours and days of recovery following surgery, makes this type of blood clot more likely. 


To prevent unwanted clotting, medications are given that reduce the ability of the blood to clot after surgery. Some of these medications, such as heparin and coumadin, require frequent monitoring of blood tests to determine if the blood is thin enough, or too thin. The dosage is then adjusted based on blood test results.

This medication may also be given if a heart attack is suspected or diagnosed. This is to help prevent damage to the heart muscle from any clots or blockages that may be present. 

Lovenox is also used as a treatment when clots form, not just as a preventative medication. If you have a blood clot, Lovenox may be part of your ongoing treatment and may be given with other medications. 

Lovenox, unlike heparin and coumadin, does not require these frequent blood clotting tests and dosage adjustments. It is safer to use at home as the chances of having blood that is too thin are significantly decreased. 


Lovenox can be given as an IV medication or as an injection into the fatty layer that rests directly below the skin. IV administration is rarely done outside of the hospital, the injection is much more commonly prescribed. It is usually given in the abdomen, and the site is typically rotated, meaning a different area of the abdomen is used for each injection, rather than using the same area over and over. 

If you are taking this medication at home, you will typically be given a pre-filled syringe with the correct dose. The needle is quite small, it is similar to what diabetics use to inject insulin. You will need to clean the injection site with an alcohol pad, allow the alcohol to dry completely, then administer the injection. 

Common Side Effects

Lovenox can cause a decreased platelet count. Platelets are one part of the blood that causes the blood to clot. Too few platelets can mean significant bleeding.

Bleeding will be increased if you have an injury. Even a paper cut can bleed longer than is typical for you while taking any blood thinner.

Women of childbearing age should be aware that Lovenox can increase menstrual bleeding, and excessive bleeding should be reported.


  • It is not uncommon to have small bruises where Lovenox is administered, this is normal and extended use of this medication may result in multiple bruised sites.
  • Lovenox should not be used during pregnancy or breastfeeding unless the risks of treatment are outweighed by the benefits of use.
  • This medication should be used with caution in individuals with severe kidney disease. For these individuals, heparin may be a safer alternative and prevent kidney damage.
  • Adults 75 years of age and older are typically given heparin rather than Lovenox, as kidney function often decreases with age. 
  • A head injury can be very severe when taking a blood thinner. Not only do head wounds bleed more than other types of wounds normally, an injury to the brain that causes bleeding can be catastrophic if the blood is very thin.
  • Notify your healthcare provider if you notice signs of abnormal bleeding, such as bleeding gums, nose bleeds, or the inability to stop bleeding from any type of injury. Blood in the stool should also be reported immediately. 
  • The risk of bleeding is increased if you take additional medications to prevent clotting, such as aspirin.

A Word From Verywell

Blood thinners by their very nature will make an individual bleed more easily. This is both a benefit and potential problem, as forming blood clots is bad, but bleeding too much is also bad--both can be life-threatening when severe. For the vast majority of surgery patients an ounce of prevention is worth a pound of cure, so most will receive a blood thinner in the early days of recovery.

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