A blood clot occurs when blood congeals, which is essential to prevent excessive blood loss from wounds. However, if this happens inside a person’s leg or elsewhere in the body, it can cause severe problems. Some blood clots are especially dangerous, as they can travel to a person’s lungs, causing a pulmonary embolism that can be fatal.

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The Agency for Healthcare Research and Quality (AHRQ) notes that the symptoms of a blood clot in a person’s leg include swelling, flushed skin, pain in the leg, and the leg feeling warm to the touch. The Centers for Disease Control and Prevention (CDC) note that if a blood clot happens in a larger vein, such as in the lower leg, it is a deep vein thrombosis (DVT).

The AHRQ says that blood clots are more likely to occur if a person is unable to move around a lot. Insufficient movement can occur due to surgery, an injury, or sitting down for an extended period, such as on a long-haul flight.

Keep reading to learn more about blood clots in the leg, including how to prevent and treat them.

Although DVT can sometimes cause obvious symptoms, it can also be asymptomatic.

What does it feel like to have a blood clot in the leg?

Possible symptoms of a blood clot in the leg include:

  • Swelling: A clot can cause the affected leg to swell to the extent that it appears much larger than the other leg.
  • Pain or cramping: If a person feels soreness or pain in the leg that was not there before, this could indicate a blood clot in the leg.
  • Pitting edema: This swelling of the leg occurs as a result of fluid buildup. DVT is a common cause of edema.
  • Discolored skin: The skin on the leg may be a different color or shade than the surrounding skin.
  • Pain: Pain may occur in the part of the leg where the blood clot has developed.
  • Warmth: The swollen skin may feel warm to the touch.
  • Shortness of breath: Chest pain can accompany shortness of breath, which can come on suddenly.

Blood clot symptoms in children

Pediatric thrombosis is the term for a blood clot in a child. When children present with a blood clot, their symptoms can include swelling in the affected limb, an increase in the temperature of the skin over the affected area, and pale, red, or blue coloring of the skin. This may be more challenging for doctors to recognize in children with dark skin.

Children with a blood clot can also present with difficulty breathing and tachycardia, which is an elevated heart rate. In some cases, there can be signs of right heart failure.

According to the National Heart, Lung, and Blood Institute, a person should contact a doctor immediately if they suspect that they have DVT. DVT can result in a pulmonary embolism, where the blood clot moves to a person’s lung.

The symptoms of a pulmonary embolism include:

  • shortness of breath
  • pain when breathing
  • rapid breathing
  • increased heart rate

If pediatric thrombosis progresses to a pulmonary embolism, the child may also experience coughing, fainting, and hemoptysis, which is blood in the lung sputum.

According to the AHRQ, risk factors for a blood clot include:

  • having had surgery recently
  • being older than 65 years of age
  • using hormonal birth control
  • receiving treatment for cancer or having had cancer
  • having a broken hip, pelvis, or leg
  • sustaining a bad bruise
  • having obesity
  • staying seated or in bed for long periods
  • having had a stroke
  • being paralyzed
  • having a port in the body through which a doctor administers medication
  • experiencing issues with veins
  • living with heart problems
  • having had a blood clot previously or having family members who have had blood clots

As a variety of other conditions can present with similar symptoms, a doctor will likely recommend specialized tests to determine whether a person has a blood clot in their leg. These may include:

  • duplex ultrasonography, which uses waves to determine whether there is a problem with a person’s blood flow
  • MRI scans
  • pulmonary angiography, which is an X-ray that uses a catheter to view the veins and arteries
  • contrast venography or a computed tomographic pulmonary angiogram (CTPA), which are special X-rays that use a dye

Another possible test is the D-dimer blood test, which checks for D-dimers — protein fragments that the body produces when a clot breaks up. However, a person can test positive for conditions other than a blood clot. Due to this, other tests are necessary alongside the D-dimer test to confirm a blood clot.

A person with a blood clot in the leg or a DVT will likely receive some of the following treatments:

  • anticoagulants or blood thinning medications, such as the injection heparin or the tablet warfarin
  • thrombolytics or clot-busting medications, which doctors usually reserve for severe cases
  • inferior vena cava filter placement, which is a surgical procedure that can help trap a moving blood clot
  • thrombectomy or embolectomy, which are surgical procedures to remove the clot

According to the CDC, the best way to prevent a blood clot or DVT is to maintain a moderate weight, avoid a sedentary lifestyle as far as possible, and follow any lifestyle recommendations from a doctor.

The CDC also recommends that people get up and walk around regularly and exercise their leg muscles while seated for extended periods.

A person could try:

  • raising and lowering their heels while keeping their toes on the floor
  • raising and lowering their toes, keeping their heels on the floor
  • tightening and releasing their leg muscles

According to a 2014 study, taking a low dose of aspirin might be effective in reducing the chances of developing blood clots or DVT.

Below, we answer some of the questions that people commonly ask about blood clots.

Should I be worried about a blood clot in my leg?

Anyone who is experiencing any of the symptoms of DVT should speak with a doctor urgently or go to the emergency room. If a blood clot in the leg goes untreated, it can progress to pulmonary embolism, which is a life threatening condition.

What are the first signs of a blood clot?

In the early stages of DVT, a person may notice some pain, swelling, warmth, or discoloration in the affected area of the leg.

What does a blood clot look like?

Visually, a person may notice some discoloration, such as redness or a bluish color on the affected area of the leg. This may be harder to see on dark skin.

How can I tell whether it is a bruise or a blood clot?

A blood clot usually causes additional symptoms that a bruise does not, such as warm skin. The different causes may also be a clue. If a person has sustained an injury to the area, they likely have a bruise. On the other hand, if they have spent prolonged periods sitting still, a blood clot is possible. Visually, however, it may be hard to tell the difference. Learn how to tell whether it is a blood clot or a bruise.

It is possible to minimize the risk of developing a blood clot or DVT by avoiding clear risk factors and practicing prevention techniques, such as exercising the muscles regularly when sitting for extended periods.

Anyone who suspects that they have had a blood clot in their leg should contact a doctor immediately.