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COVID-19 and blood clots

Written by Ada’s Medical Knowledge Team

Updated on


  • COVID blood clots are more likely to appear if you’ve been hospitalized due to your illness.
  • Underlying health conditions such as obesity, high blood pressure, and blood conditions can increase the risk of COVID-19 blood clots.
  • If you notice signs of a blood clot, then it’s important to seek medical attention immediately.

Studies have shown an important link between COVID-19 and blood clot formation. An infection with the coronavirus could trigger the formation of blood clots. COVID blood clots can be life-threatening, but the good news is that early detection and treatment can make a big difference in the outcome of the condition. In this article, we’ll run you through the link between blood clots and COVID-19, the importance of the COVID-19 vaccine, and the warning signs that you should look out for.

Can COVID-19 cause blood clots?

COVID-19 can cause blood clots in some people. Your risk of blood clots after COVID-19 is particularly higher if you’ve experienced severe symptoms due to the infection and ended up in the hospital as a result. Blood clots can appear anywhere in the body, from the veins that transport the blood to the heart, to the arteries that transport the blood from the heart to the rest of the body. Scientists believe that there are a number of reasons behind the formation of these blood clots: 1 2

  • COVID blood clots could be the result of being immobile during your illness. If you’re feeling very unwell or if you end up in the hospital, then you tend to lie down for the majority of the time during your illness. During such an immobile period, the risk of developing blood clots increases significantly. 
  • Blood clots from COVID-19 could develop as a result of the virus attacking the inner lining of the blood cells. This causes the immune system to activate in order to kill the virus. This immune response can cause blood clots in some cases. 
  • COVID blood clots could also happen due to the high levels of inflammation caused by the infection. This inflammation can affect multiple organs, including the heart and blood vessels. 

Who is at risk of developing COVID blood clots?

COVID blood clots can occur in anyone, but they’re more common in people who have experienced severe symptoms and require hospitalization. Several factors can increase the risk of developing blood clots, including: 2

What are some COVID-19 blood clots symptoms?

COVID blood clots can happen in several parts of the body, including the smaller veins and arteries. Blood clots that happen in a vein of the legs are called deep vein thrombosis, which can move to the lungs and can block an artery here. This condition is called a pulmonary embolism and may be life-threatening if not treated quickly.

A blood clot can also occur in the arteries that provide blood flow to the heart. This can result in a heart attack. COVID blood clots can also cause a stroke when the blood clot blocks the blood flow to the brain. 

Post-COVID blood clot symptoms can vary depending on the place where the blood clot is obstructing an artery or a vein. You may experience: 4

  • Throbbing or cramping pain in a leg or an arm 
  • Swelling, redness, and warmth in a leg or arm 
  • Sharp chest pain that gets worse when breathing in 
  • Sudden breathlessness
  • Coughing up blood
  • Feeling faint 

If a stroke is happening, then there are some warning signs that happen suddenly, such as: 5 

  • Weakness or numbness in the face, arm, or leg. This mostly happens on one side
  • Trouble speaking
  • Trouble seeing
  • Confusion
  • Trouble walking
  • Dizziness
  • Loss of coordination
  • Severe headache

Does the COVID vaccine cause blood clots?

There have been some cases reported of blood clots appearing after COVID-19 vaccination. This was specifically the case for people who received an mRNA-based vaccine. However, this complication after vaccination is rare and can be treated effectively when diagnosed and treated early on. It’s still important to get vaccinated and to keep your vaccination up to date, as the benefits of COVID-19 vaccination far outweigh the possible risks.6

How to prevent blood clots with COVID?

There are various things that you can do to help prevent COVID blood clots: [8]

  • Be active
  • Avoid sitting down for long periods without moving 
  • Drink plenty of water
  • Tackle underlying health conditions such as obesity 
  • Avoid drinking alcohol and smoking 

If you do notice any of the signs of a blood clot after COVID-19, then you should seek medical help as soon as possible. Early diagnosis and treatment can make a big difference in the outcome of your condition.

Wrapping up

COVID blood clots are an essential consequence of an infection with the coronavirus, and you should be aware of them, especially if you’ve been hospitalized due to your illness. If you’re experiencing any signs of blood clots, it’s important to seek immediate medical help. 


Q: Why does COVID cause blood clots? 
A: Scientists believe that COVID may cause blood clots due to the high degree of inflammation throughout the body, the virus attacking the inner lining of the blood cells, and the fact that people with severe COVID often tend to lay down for longer periods of time. 

Q: Does the COVID vaccine cause blood clots? 
A: There have been reports of blood clots after COVID-19 vaccination, especially for mRNA vaccines. However, the risk of blood clots is rare. 

Q: How to test for blood clots after COVID?
A: There are ways to check for blood clot risk, such as a thromboelastography.