How do I know if I have a blood clot?

There has been a lot of talk lately about blood clots, especially since the news about the low risk of developing them after receiving the AstraZeneca or Johnson & Johnson covid-19 vaccines. However, the average person doesn’t actually know much about blood clots and how they occur. The reality is that plenty of everyday things we do increase our risk of blood clots, far more than these vaccines. Nonetheless, everyone must know the signs of a blood clot to prevent a catastrophe, regardless of which vaccine they end up getting. 

What Is A Blood Clot?

Whenever we hear the term “blood clot,” we always automatically think of something negative. In reality, blood clotting is a natural and important physical response to trauma. If our blood didn’t clot, even minor cuts and scrapes could cause us to bleed out until we die. Those clots then eventually dissolve when the wound is healed. (1)


Sometimes blood clots can move around the body when the situations that induced the clotting overwhelm those that dissolve them. If these clots don’t dissolve and grow too big, they can get stuck in places while passing through different organs, such as the lungs, heart, or brain. This, as you can imagine, can cause some serious health problems. (1)


The Signs Of A Blood Clot

As you can imagine, it is essential for us to know the signs of a blood clot to get proper medical attention before we have a heart attack, stroke, or other life-threatening health problem. Firstly, there are actually two types of blood clots: Arterial (in your arteries) and venous (in your veins). Arterial blood clots cause many symptoms very quickly and require immediate medical attention. Venous blood clots develop slowly over time but can be just as fatal. (2) Blood clots will often form in the legs, arms, heart, abdomen, brain, and lungs. The symptoms of each can vary a little. (2) Types of clots include:


Arm Clots

Signs of a blood clot in your arm include (2):

  • Swelling
  • Pain and tenderness
  • A warm sensation
  • A reddish discoloration

Clots In The Heart

Signs of a blood clot in your heart include (2):

  • Chest pain or a feeling of heaviness in the chest
  • Lightheadedness
  • Shortness of breath

Blood clots in your heart will cause a heart attack, so if you have symptoms, seek medical attention immediately. (2)


Clots In The Abdomen

Signs of a blood clot in the abdomen include (2):

  • Abdominal pain and swelling

This doesn’t always signify a blood clot, but regardless of the cause you should visit your doctor. (2)


Clots In The Brain

Blood clots in the brain cause stroke. Signs of a blood clot in the brain include (2):

  • A sudden, severe headache
  • Sudden difficulty seeing or speaking

Clots In The Lungs

This is also known as a pulmonary embolism. Symptoms include (2):

  • Sudden shortness of breath (not exercise-induced)
  • Chest pain
  • Rapid heart rate or palpitations
  • Breathing problems
  • Coughing up blood

Who Is At Risk For Blood Clots?

There are many risk factors for developing blood clots. The CDC estimates that pulmonary embolism combined with deep vein thrombosis (a clot that forms in a major vein deep inside our body) affects up to 900,000 Americans every year and kills about 100,000. (2) Risk factors include (2):

  • A recent hospital stay, particularly long ones or those related to major surgery
  • Age (65+ especially)
  • Long-haul travel causes you to have to sit for long periods of time
  • Bed rest or long periods of sedentary behavior
  • Obesity
  • Pregnancy
  • Family history
  • Smoking
  • Cancer
  • Some birth control pills

It is important that you discuss your risk factors with your doctor to ensure you have a proper plan in place to avoid developing blood clots and the health problems associated with them. (2)

What’s The Deal With Blood Clots And The COVID-19 Vaccine?

Recently, the Oxford-developed COVID-19 vaccine AstraZeneca made headlines after a few people developed a rare clotting disorder after receiving the vaccine. The difference between regular blood clots and vaccine-induced clots is that these clots are smaller yet have caused some people to have some pretty big problems. (3) That being said, the instance of developing this disorder is extremely rare – much less than the instance of blood clots from, for example, some birth control pills. (4) The director of the European Medicines Agency (EMA) Emer Cooke reminds us all that this side effect is extremely rare. (3)

“The risk of mortality from COVID is much greater than the risk of mortality from these side effects.” she explained. (3)

Still, researchers are trying to figure out why a vaccine would cause such a reaction at all. There are a number of factors that go into making a vaccine that could be the culprit. (3)

 “Of course, there are hypotheses: maybe it’s something with the vector, maybe it’s an additive in the vaccine, maybe it’s something in the production process … I don’t know,” says Sabine Eichinger, a hematologist at the Medical University of Vienna. “It could be any of these things.” (3)

More Investigations Being Done

Despite the low risk of you actually developing this clotting disorder, the EMA is still conducting several investigations to determine who has the highest risk and what might actually be causing it. They have also asked AstraZeneca to investigate their vaccine themselves to solve this problem as soon as possible. (3)

Should You Or Should You Not Get The AstraZeneca Vaccine?

As most health professionals have said already, the best vaccine for you to get is the one you can get first. The risk of developing this clotting disorder from AstraZeneca is low, and you are far more likely to suffer consequences from catching COVID-19 than from the vaccine. That being said, it is your body, your health, and therefore your choice. If you are concerned, talk to your doctor about whether or not you think this vaccine is the right one for you. After all, there are several other options that you can get to protect you from this deadly virus.

Keep Reading: 9 Signs Your Body Sends You When Something May Be Wrong


  1. Vaccine side effects: With all this talk about blood clots, how do I know if I’m affected?ABC. Malcolm Sutton. April 14, 2021.
  2. How to Tell If You Have a Blood Clot.” Healthline. Juliann Schaeffer. March 26, 2019.
  3. How could a COVID vaccine cause blood clots? Scientists race to investigate.” Nature. Heidi Ledford. April 9, 2021.
  4. Blood clot risks: comparing the AstraZeneca vaccine and the contraceptive pill.” The Conversation. Adam Taylor. April 10, 2021
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Julie Hambleton
Freelance Writer
Julie Hambleton has a BSc in Food and Nutrition from the Western University, Canada, is a former certified personal trainer and a competitive runner. Julie loves food, culture, and health, and enjoys sharing her knowledge to help others make positive changes and live healthier lives.