Is it possible for someone to get a deep vein thrombosis while on the blood thinner coumadin (Warfarin), and if so, why?

This is a prescription drug that’s so effective at thinning blood, that it carries the risk of internal bleeding, including in the brain.

Once a definitive diagnosis is made,  the patient is placed on anticoagulation, which typically is that of coumadin (Warfarin), says Dr. Kurtis Kim, MD, a vascular surgeon with Vein & Vascular Institute of Central Maryland.

A common reason for being placed on a blood thinner is to help prevent DVT as a result of surgery, particularly joint replacement.

Joint replacement surgery is notorious for heightening the risk of a blood clot. Abdominal surgery is another type of operation that will put the patient at high risk for a deep vein thrombosis.

Dr. Kim explains that a “very small percentage of people who develop DVT” are on a blood thinner.

And when this does happen, “one must ask the following questions:

#1) Is this patient compliant with this medication?” and

#2) “Is the medication at a therapeutic level (for example coumadin needs to be dosed to achieve an INR of 2-3).”

The third check is to review other risk factors for a deep vein thrombosis.

INR stands for international normalized ratio. It’s a numerical value that correlates to how long it takes the blood to clot. The higher the number, the longer it takes.

The first time someone takes coumadin, the INR will not be in the therapeutic (or DVT prevention) range.

It has to build up. And it fluctuates, which is why when someone is prescribed coumadin to take for a while, they must have regular blood draws to make sure that the INR is within therapeutic range.

After my father fell and hit his head, resulting in neurological symptoms, the doctor reduced the coumadin dose to bring the INR down to 1.5.

He had had knee replacement surgery a week prior, and the fall resulted from passing out—for reasons that still remain somewhat of a mystery, though the best theory is that his blood pressure had plummeted as a result of drug interactions.

The INR was dropped to 1.5 because he was at risk for having a brain bleed from the fall.

However, after he was released from the hospital, the doctor increased the coumadin dose and the targeted INR.

Coumadin is very effective at DVT prevention, but it’s not 100 percent guaranteed to prevent a deep vein thrombosis.

Specializing in minimally invasive procedures, Dr. Kim combines medical expertise with a caring approach to diagnose and treat patients with circulatory issues including leg pain, swelling and blood clots in the legs and lungs.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  


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