Blood Clot Symptoms: How to Tell if You Have One

Medically Reviewed by Jabeen Begum, MD on May 30, 2024
Written by Angela McPhillips
8 min read

Ever get a paper cut or nick yourself while shaving? When that happens, a blood clot saves the day. A blood clot is a collection of blood cells and other substances that come together to stop bleeding. The clot, a gel-like mass, quickly stops the bleeding, and it usually breaks up after its job is done. Sometimes, though, things can go wrong.

When blood clots don't fall apart, they can be dangerous and lead to serious medical conditions. You can get them in blood vessels in just about any part of your body. They’re most likely to affect a leg, especially if you sit for long periods.

You might get a clot in your arteries, which carry oxygen in your blood from your heart to all the cells of your body. The result can be really serious. It can keep oxygen from getting to your heart, lungs, or brain, and cause a life-threatening emergency, such as a heart attack or stroke.

You could also get a clot in the veins that carry blood back to your heart. When that happens, symptoms usually come on more gradually, but can still mean trouble.

If you learn the warning signs, you’re more likely to get quick medical help that can make a huge difference in keeping you out of the danger zone. But it’s important to know that in some cases, clots can happen with few symptoms or none at all.

Deep vein thrombosis in the leg

When a blood clot forms in one of the deep veins in your arm or leg, way beneath your skin's surface, it could be something called a deep vein thrombosis (DVT). That's dangerous because the thrombus, or clot, could travel to your heart or lungs.

You're more likely to get a DVT in your leg if you haven't moved around for a long time, say after surgery or during a long plane trip.

Symptoms of deep vein thrombosis in the leg

If you have a blood clot in your leg, you may experience some or all of these symptoms:

  • Swelling. Your whole leg, or just the exact spot where the blood clot forms, may swell up. The swelling may quickly progress to pitting edema — a buildup of fluid that leaves a “pit” or dimple if you press on your leg.
  • Color change. Your affected leg may change color — red or purple — depending on your skin color.
  • Pain or lower leg cramp. You may have pain in your whole leg or a cramp that starts in your lower leg or calf. This cramp might feel like a bad charley horse. You may only feel pain when you stand or walk.
  • Warm skin. The skin on your leg with the DVT may feel warmer than other skin when you touch it.

Sometimes, you can have a DVT without any symptoms. But a leg DVT can get worse and become a medical emergency. If you have these symptoms, it's important to call your doctor right away or go to the emergency room.

Deep vein thrombosis in the arm

Arm DVTs don’t occur very often. They’re more common in young, healthy people (especially athletes) after intense arm activity, such as wrestling, swimming, or repeated ball throwing.

Deep vein thrombosis in arm symptoms

  • Swelling. Your arm may suddenly swell up.
  • Color change. The skin on your arm may change colors. It may look red or purple. Or your skin may be pale or have a blue tint.
  • Visible veins. The veins in your arm and chest may stand out more than usual or even bulge. 
  • Arm pain and heaviness. Your arm may hurt and feel heavy and tired. You might have trouble moving your arm.

Like a leg DVT, a DVT in your arm can also be a medical emergency. So contact your doctor or go to the emergency room if you have these symptoms.

Blood travels in arteries from your heart to the rest of your body. Blood clots can sometimes form in the arteries in and around your heart. This is more likely to happen if you have atherosclerosis, a buildup of a sticky substance called plaque on the insides of your arteries. Plaque can sometimes break away or burst and a blood clot can block the area where that happened. When a blood clot blocks the arteries in your heart, your heart muscle doesn’t get the blood and oxygen it needs to beat and stay healthy. This may cause a heart attack.

A heart attack is a medical emergency that needs medical treatment right away to save your life. Watch out for symptoms such as:

  • Severe pain in your chest and arm
  • Crushing chest pain, such as an elephant is sitting on your chest
  • A feeling of squeezing or heaviness around your chest
  • Sweating
  • Trouble breathing
  • Nausea or stomach pain
  • A racing heart
  • Dizziness, lightheadedness, or fainting
  • Anxiety or a sense of doom

Pulmonary embolism

Blood travels in veins from your body to your lungs. A blood clot or DVT in your arm or leg can break free and make its way to your lungs. This clot can enter your lung and cause a blockage. When this happens, you get what's called a pulmonary embolism (PE), a life-threatening condition. PE blocks blood flow to the lungs and requires immediate treatment.

Pulmonary embolism symptoms

Get medical help right away if you experience the following:

  • Sudden shortness of breath or trouble breathing
  • A sharp pain in your chest when you take a deep breath
  • A cough with or without bloody mucus
  • A lot of sweating
  • Dizziness or fainting
  • Clammy or pale skin

Blood clots in the brain may be caused by fatty deposits in the walls of the blood vessels, or arteries, that bring blood to your brain. Sometimes, they may form because of a blow or injury to your head that leads to a concussion.

Stroke

A clot that starts in a different part of your body, such as your chest or neck, might enter your bloodstream and travel to your brain. This clot then blocks blood flow and oxygen to your brain. When this happens, you have an ischemic stroke. This is a medical emergency that needs immediate lifesaving treatment. Call 911 if you or someone around you has signs of a stroke. The faster you are treated for a stroke, the less damage there will be to your brain.

Signs of a stroke

Watch out for these symptoms:

  • Sudden loss of balance
  • Sudden trouble seeing with one or both eyes
  • Drooping on one side of the face or an uneven smile
  • Weakness on one side of the body
  • Slurred speech or trouble saying the right words

Blood clots can happen in the veins that drain blood from your intestines, or bowels. They can be caused by conditions such as diverticulitis (inflammation of the large intestine), liver disease, or even by birth control pills. A blood clot in your belly, sometimes called superior mesenteric vein (SMV) thrombosis, is dangerous because it can block blood flow to your intestines and other organs in your belly. Without blood flow, you can have organ damage. So, it’s important to get medical treatment quickly to prevent complications and stay healthy.

Abdominal blood clot symptoms

How will you know if this is going on? Check with your doctor if you have problems such as:

  • Nausea or vomiting, with blood in your vomit
  • Severe pain in your belly, which may be worse after you eat
  • Diarrhea
  • Blood in your poop
  • A bloated feeling

Depending on the type of blood clot you have in your belly, you may have mild or severe symptoms. Sometimes, you won’t have any symptoms at all. So, it’s important to see your doctor if you have any new or worsening belly pain or other health concerns. Your doctor will help you figure out the reason and get the right treatment.

Your kidneys remove waste from your body and make pee. A blood clot can block blood flow to your kidneys and is called a renal vein thrombosis. This keeps your kidneys from working the right way and can cause many symptoms leading up to kidney failure.

Kidney blood clot symptoms

A blood clot in your kidneys is dangerous, so look out for these symptoms:

  • Pain in the side and back of your abdomen, between your lower ribs and hips
  • Blood in your pee
  • Peeing less
  • Fever
  • Nausea or vomiting
  • Sudden severe leg swelling (rare)

A blood clot is a collection of blood cells and other material that forms to stop bleeding if you have a cut or are injured. Sometimes, blood clots don’t break apart after they’ve done their job. This can cause lots of problems in different parts of your body. Blood clots can form in your arms, legs, brain, heart, belly, or kidneys, which may cause a medical emergency such as a heart attack or stroke. Call your doctor or 911 right away if you have symptoms of a blood clot.

What are the warning signs of a blood clot?

Warning signs depend on the location of the blood clot. In general, look out for the following: arm or leg pain or swelling, redness or pain over the location of the clot, trouble breathing, chest pain, dizziness or fainting, belly or back pain, and signs of stroke such as loss of balance, one-sided weakness, or slurred speech.

How do you know if you have a blood clot?

The only way to know for sure is to see your doctor. Your doctor can do tests such as an ultrasound, CT scan, and even a blood test to see if you have a blood clot.

Who is at risk of blood clots?

People who recently had surgery, are not physically active, are 65 or older, take hormones (especially for birth control), have a broken bone, are obese, smoke, and have a history of stroke, heart trouble, and past blood clots are most at risk. People who have been sitting for long periods such as on a plane or long car ride are at risk of getting a leg DVT.

How can you stop blood clots?

There are steps you can take to stay healthy and prevent blood clots. Stay active and take movement breaks after long periods of sitting. Drink lots of water and maintain a healthy weight. Don’t smoke if you aren’t a smoker, and take steps to quit if you are.