Blood Thinners Before and After Surgery

Blood Tests Image
Blood Tests Will Determine Your Dose of Blood Thinners. Image: © Nicholas Everleigh/Getty Images

It is very common to take a blood thinner after surgery​, especially if you are spending a day or two recovering in the hospital.  Blood clots are always a concern in people who are spending a lot of time in bed, or sitting.  That means people who are taking a long flight are at risk, as are people who have a long surgery that keeps them still for many hours, or even patients who are spending most of their time in bed in the days after surgery.


To prevent blood clots after surgery, medications are often given that “thin the blood” which means the blood takes longer to clot.  It will clot, just not as quickly as it would without medication.  This delay in clotting decreases the risk of forming a blood clot.  It also increases the risk of bleeding, and something as simple as a paper cut could bleed longer than usual.

Risks of Blood Thinners

The primary risk of using a blood thinner, as you may imagine, is bleeding.  Too much of a good thing, even a medication that prevents blood clots, can be a problem.  Suddenly something as simple as a nose bleed or a paper cut leads to more bleeding than normal.  

Blood thinners can also lead to other types of bleeding.  Imagine falling and hitting your head on some slippery ice.  Normally, you would get a bump on your head but with blood thinners in your system there is a potential for bleeding in your brain.

  For this reason, it’s a good idea to avoid adventurous activities and impact sports while you are taking a blood thinner.  In the days following surgery, you probably won’t be interested in  trying your hand at boxing or rock climbing, but if you were considering it, you really shouldn’t.  

Wait, I’m Already on a Blood Thinner!

If you are already on a blood thinner prior to surgery, you may be asked to stop taking it in the days prior to surgery.

  While slower clotting is desirable after surgery, being more likely to bleed during surgery is not.  The risk of stopping your blood thinner for a few days prior to surgery is low, and will help prevent too much bleeding during surgery.

If you are taking a blood thinner, even if it is an aspirin a day, be sure to discuss this with your surgeon.  You should have a plan for when to take it and when to decrease your dose in the days prior to surgery.  

About Supplements

Some over the counter supplements are known to increase the risk of bleeding.  Please discuss any vitamins, minerals and supplements you are currently taking with your surgeon.  

Common Blood Thinning Medications

Aspirin: This is the least expensive option for preventing clots and is available over the counter. Aspirin works by increasing the amount of time it takes for your body to form a clot. It is often encouraged to be taken daily for older patients to help prevent stroke and heart attacks.  A daily dose is typically 81mg but may be as high as 325mg for some patients.

  Patients may receive aspirin in the hospital, and typically return to their daily aspirin therapy after surgery.

Heparin: This medication is typically used in the hospital and is given as an injection into the flesh of the abdomen as often as three times a day. It can also be given as an IV medication.  It is not typically taken at home, as it requires regular monitoring of blood tests.  

Coumadin (Warfarin):  Often taken at home in pill form, Coumadin also requires frequent monitoring and can be greatly affected by diet.  Coumadin increases the length of time it takes your body to form a clot, and is frequently used by people with heart conditions that can lead to clot formation.  In the hospital setting, this blood thinner is typically used for patients who routinely take the medication before surgery, and they are often discharged home with instructions to continue taking this prescription.

Lovenox: Also known as low molecular weight heparin, Lovenox is typically used in the hospital.  Like heparin, it is given as an injection into the fatty tissue of the abdomen, and is typically not used at home.  You may receive Lovenox injections during your hospitalization but you don’t typically go home with this medication.

Plavix: This medication is taken as a pill and is typically used for a long term preventative of clots in patients at risk of stroke or heart attack.

Commonly Used Medications In Surgery


Blood Thinners. Medline Plus. Accessed August, 2015.

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