These Are The Symptoms Of A Blood Clot And How To Prevent Them

Most people probably don’t think about blood clots on a regular basis. But with reports of a small number of people developing blood clots after they received either the Johnson & Johnson or the AstraZeneca COVID-19 vaccine, many people are now wondering what the warning signs are.

There are several different variations of blood clots, each with its own set of red flags and options for treatment. They can form for a number of reasons, including medication, lifestyle factors and other health conditions, and they can occur in different parts of the body.

All that said, blood clots can cause severe harm or be fatal if left unaddressed. If you’re concerned ― whether it’s because of a vaccine or, more likely, something else ― read on for the signs to pay attention to, and advice on what to do if you think you’re at risk.

Symptoms Of Blood Clots

Blood clots can originate in the veins or arteries. There are two main types of blood clots to be aware of, and each can lead to its own set of potential complications. One type is called a thrombus, which is a stationary clot. These block blood flow in the part of the body where the clot occurs. Another type, called an embolus, is a blood clot that can break loose. These are particularly dangerous because they can travel to other parts of the body ― like the heart or the lungs ― and cause severe damage.

The symptoms of blood clots vary depending on the type. When the clot is stationary, like deep vein thrombosis (a clot in your leg), you may experience:

  • Warmth and redness where the clot is located ― typically in the leg or the arm

  • Swelling

  • Pain near the site of the clot

  • Numbness or weakness

  • A change in your mental state

If the clot has traveled, leading to complications like a pulmonary embolism (a clot that has moved to your lungs), you may experience symptoms including:

  • Sudden shortness of breath

  • A cough, with or without blood

  • Clammy, pale or blue skin

  • Excessive sweating

  • Anxiety

  • Weakness

  • Nausea or vomiting

Blood clots can affect your arms, legs, heart, lungs, kidneys and brain, depending on where they form and where they travel in the bloodstream.

A handful of people who received the Johnson & Johnson vaccine developed complications from a clot originating in the veins near the brain, called cerebral venous sinus thrombosis, or CVST. This issue is seen in combination with low levels of blood platelets. (A few people who received the AstraZeneca shot experienced clots caused by the same issue, but since the AstraZeneca dose isn’t yet approved for use in the United States, this story will focus on J&J.)

Symptoms associated with this type of clot complication include severe headache, abdominal pain, leg pain or shortness of breath within three weeks after vaccination, according to the Centers for Disease Control and Prevention and the Food and Drug Administration.

A few important notes when it comes to the J&J vaccine: Blood clots following the shot appear to be extremely rare ― as of now, there are only six reported cases out of nearly 7 million doses of the vaccine that have been distributed ― and have occurred within 13 days of vaccination. You have a higher risk of developing blood clots from an actual COVID-19 infection.

“Just remember that COVID-19 causes blood clots,” infectious disease expert Amesh Adalja told HuffPost for a separate story. “And COVID-19 causes blood clots at a higher rate than the vaccine does.”

Experts emphasize that the vaccine could be a game changer for the pandemic, and a principal reason for the pause in distribution is to inform health care providers how to spot, treat and report the issue. Don’t let this deter you from getting any vaccination against the coronavirus.

Pay attention to the warning signs of blood clots and seek help right away. (Photo: SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY via Getty Images)
Pay attention to the warning signs of blood clots and seek help right away. (Photo: SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY via Getty Images)

What To Do If You Suspect You Have A Blood Clot ― And How To Prevent Them

First and foremost, seek emergency medical care right away. Blood clots can be severe or fatal, so if you suspect you have one, it’s crucial you get it addressed. When in doubt, call 911 or go to the emergency room ― especially if you have the symptoms listed above, along with chest pain or trouble breathing.

Once you’re with a health care provider, inform them of any history of medical conditions, medications or recent vaccinations. This is particularly important if you just received the Johnson & Johnson COVID-19 vaccine, as treatment for that particular clotting issue is different from what physicians normally do to address blood clots.

In the long term, chat with your doctor about reducing your overall risk of blood clots. Let them know about any family history of the issue as well.

Certain lifestyle factors can increase your chances of blood clots. For example, being inactive or immobile for long periods of time ― like during a long flight or while on bed rest ― can be a contributor. Smoking and obesity can also increase your risk.

Medications like birth control and some HIV treatments list blood clots as a potential side effect. Conditions like autoimmune disorders, pregnancy and cancer have also been associated with clotting, according to the American Heart Association.

If you’re going to be traveling or in a situation where you’ll be immobile for a long period of time, be sure to exercise, stretch and move your legs frequently to improve blood flow ― particularly in your calves. You may also benefit from wearing compression socks. As for other prevention methods, talk to your doctor. Depending on your health history and current diagnoses, your physician may suggest certain treatment paths that can help you address any of these potential complications. This may include a plan for diet, exercise, medication or all of the above.

If you suspect you’re dealing with a blood clot, don’t put it off. It’s better to address what turns out to be nothing than ignore what turns out to be something. And it pays to be vigilant about your health.


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This article originally appeared on HuffPost and has been updated.