DVT and COVID-19: What Are the Links?

Medically Reviewed by Brunilda Nazario, MD on February 19, 2021
6 min read


During the COVID-19 pandemic, doctors have seen more cases of blood clot-related conditions like deep vein thrombosis (DVT). It's concerning because studies show that having a blood clot while you have the virus raises your chance of death by 74%.

Elliott Richard Haut, MD, an associate professor of emergency medicine at Johns Hopkins University School of Medicine, is one of a group of doctors and researchers around the world who are trying to figure out the connection between DVT, pulmonary embolism (PE), and COVID-19.

“There’s lots of different potential reasons,” he says. “Trying to come up with every single pathway is really hard."

Many people believe that moving around can help avoid clotting issues like DVT

But a recent study found no major link suggesting that movement alone helped lower the risk of blood clots in hospitalized people.

So while most of us are less active during the pandemic, that fact alone probably won’t trigger a blood clot.

“The reality is, a lot of illnesses may cause sedentary states, and we are seeing higher rates of COVID-19-related thrombosis than other [illnesses],” says Lucy Kornblith, MD, a surgeon at the University of California San Francisco.

She believes it’s much more likely that other issues related to the virus itself cause the rise in blood clot cases.

From the start of the pandemic, experts knew there was a tie between a higher chance of blood clots and the COVID-19 virus. To combat this, doctors looked at how they gave blood thinners to people hospitalized with the virus. They'd either get a high dose or, instead of just one dose, they'd get a continuous infusion.

But there wasn’t data to show that this plan would help. Doctors were simply doing all they could to stop blood clots amid the surge in COVID-19 cases. Soon after the virus took hold, many researchers began to study the reason for this wave of blood clot cases and the best way to lower the odds of clotting during the pandemic.

The idea was that people were either refusing their doses or, according to Haut, “the doctors were focused on other treatments [for COVID-19] and were not writing prescriptions for blood clot prevention.”

But they discovered that people with COVID-19 were more likely to get all the medication they needed -- including blood clot prevention drugs -- than first thought.

“It made us actually feel pretty good … we were doing the best we could as far as best practice,” Haut says. “But in some ways, it’s too bad, because that’s a relatively easy fix.”

Since missing doses wasn't a culprit, some researchers thought it was the amount of blood thinning drugs given to those with COVID-19. In one study, doctors gave some people a regular preventive dose of blood thinners while others got a high-dose, continuous infusion. They did this with people who were mildly sick with COVID-19 and those who were severely ill with it.

People hospitalized with COVID-19 without DVTs had better outcomes when they got the high-dose, continuous infusion, compared to those who got the preventive dose. But people who were critically ill with COVID-19 didn’t have the same results.

“If there’s no evidence of a DVT, and you give a critically ill patient in an intensive care unit (ICU) a constant infusion of a high-dose blood thinner, not only does it not benefit them, but there’s an increased risk of harm and bleeding,” says Scott Cameron, MD, section head of vascular medicine at the Cleveland Clinic.

“What that tells us is that even a little bit of data is simply not enough to make the decision of the clinician to treat a patient differently during the COVID era,” he says.

Another possible factor in the surge of DVT cases could be from a simple concept: The more you look, the more you find.

While this probably doesn’t explain the entire link between the two conditions, it could partly explain why so many more blood clots show up in those with COVID-19.

“We’ve found that doing lots of ultrasound testing finds a lot more DVT,” Haut says. “It might find DVTs that are asymptomatic and not causing issues.” Similarly, people may come into the hospital with DVTs that are unrelated to COVID-19. And doctors may find these blood clots and wonder if the virus plays a part.

Some doctors suggest that screening for DVT should happen only if someone shows symptoms of a blood clot. This will not only help researchers understand the tie between COVID-19 and clotting, but it will also lessen possible spread of the virus.

“One of the issues that’s created across the world is that we’re potentially subjecting health care workers to unnecessary risks [of COVID-19] when the patient doesn’t have any [DVT] symptoms,” Cameron says.

Whatever the reason for these blood clots, experts have taken a look at the emotional effects of a life-threatening blood clot, as well as when it's paired with COVID-19.

“We’re really interested in this post-thrombotic stress disorder because there’s no research on it,” says Rachel Rosovsky, MD, a hematology specialist at Massachusetts General Hospital.

For people with blood clots, the goal is to prevent further clots, lessen bleeding, and avoid death. While those areas are extremely important, “they don’t capture any patient-relevant outcomes: quality of life, functional ability, depression, anxiety, social isolation, unemployment, or excess health costs.”

Leslie Lake, board president of the National Blood Clot Alliance, who herself has had a life-threatening blood clot in her lungs, says she felt “terrified” after she returned from the hospital after a pulmonary embolism.

“The mental side of the equation is something that I still grapple with. It was harder for me to deal with than the actual physical event of me getting a blood clot,” she says. “I had never gone to a therapist in my life, and I went to [one] because I was so terrified that I was going to die.”

Lake belongs to many blood clot social media groups and says that people post daily about their posttraumatic stress disorder (PTSD) from the condition.

During the pandemic, the anxiety linked to life-threatening conditions, like certain blood clots, has only gone up. People are now in the ICU for days by themselves. If someone has COVID-19, they aren’t able to see loved ones or have in-person support. They may also have a blood clot, which adds another layer of fear and furthers their chances of long-term mental side effects.

It's become so prevalent that clinics now exist for people with PTSD and anxiety after a life-threatening blood clot. These are especially important during the pandemic so that we can understand not only the physical long-term effects, but the mental impacts of the virus and DVT.

“We are just starting to skim the surface of understanding the long-term effects of COVID on patients both medically as well as emotionally,” Kornblith says. “The focus has really been on that initial treatment phase, and now we have this whole population of patients who have had COVID. That really needs to be a focus going forward.”