Signs of Blood Clot in Leg: Visible and Invisible Clues

A blood clot in your leg, called deep vein thrombosis (DVT), can have severe outcomes if it remains without treatment. Getting a prompt diagnosis and the right care can reduce your risk of having severe problems.

You may not be aware you have a blood clot in your leg. In many cases, physical symptoms are dismissed as minor or a result of aging. Some blood clots may form with invisible symptoms or none at all. You may not discover you have a blood clot until it causes severe problems.

Knowing the signs of a blood clot in the leg can help you determine when treatment may be necessary. This article describes what to look for if you are at risk of a blood clot in the leg, the effects of hidden symptoms, and when to seek treatment.

Where Blood Clots Form on Legs

The most common place for a blood clot to form in the legs is in the large deep veins in your lower leg, thigh, or pelvis. These veins are the main blood vessels that return blood to your heart.

Blood clots form when an incident such as an injury or surgery to your hips or legs causes damage to the lining of a blood vessel to make it narrow. Blood clots can also develop if the makeup of your blood changes so it does not flow freely and clots form more easily.

A blood clot in your leg is dangerous because there is the risk of a piece of the blood clot breaking free. If this occurs, the clot can travel through your bloodstream and block the blood flow to your lungs. This severe problem, called a pulmonary embolism, requires prompt treatment to avoid death.

When the leg blood clot stays in place, it can cause a condition called post-thrombotic syndrome. It causes permanent damage to the valves in the veins in your leg, resulting in pain, swelling, and leg sores.

Physical and Visible Signs of a Blood Clot in the Leg

Physical and visible signs of a blood clot typically appear only on the affected leg. If you have symptoms that only occur on one side or limb while the unaffected limb remains normal, it is a strong indication that the problem is likely a blood clot.

You can feel a blood clot in your leg due to the pressure of obstructed blood building up behind the clot. The obstruction causes reduced blood flow and lower levels of oxygen available to your organs and tissues.

Symptoms of a blood clot in your leg include:

• Throbbing pain, usually centered in one area of one calf or thigh when walking or standing up, that may feel like a muscle cramp
• Swelling, which may occur suddenly, in the affected area or along a vein in the affected leg
• Redness triggered by inflammation, which typically spreads out over the affected area
• A feeling of warmth, usually a sign of inflammation, in the area of the leg that is swollen or painful
• Dyspnea (shortness of breath) that occurs for no obvious reason
• A thickening or firmness of the leg vein called a “cord”

Invisible Signs of a Blood Clot in Leg

Since the deep veins of the leg are not visible through your skin, a blood clot in your leg can be invisible.

About 30%–40% of leg blood clots go unnoticed because they do not cause typical symptoms. Some people do not know they have this condition until it advances to a pulmonary embolism and causes serious problems.

If you have leg pain, your healthcare provider will use one or more of the following tests to diagnose a blood clot in your leg:

• Duplex ultrasonography: This is the standard imaging test for diagnosing a blood clot in your leg. It uses sound waves to observe the flow of blood in your veins and detect blood clots or blockages.
• D-dimer blood test: This blood test measures levels of a substance that is released into the blood when a clot breaks up. It is used to rule out blood clots.
• Contrast venography: This test uses an X-ray and contrast dye to observe the deep veins in your leg and hip.

Lowering the Risk of Getting Leg Blood Clots

Lowering the risk of leg blood clots involves addressing the modifiable risk factors (risk factors that you can change) for this disorder. This often involves making lifestyle changes that offset the effects of limited movement, recent surgery, or advanced age.

The following strategies could lower your risk of getting a blood clot in your leg:

• Stay active and move around as much as possible.
• Wear loose-fitting clothing, especially socks and stockings.
• Wear compression stockings if your healthcare provider prescribes them.
• Raise your legs 6 inches above your heart at regular intervals throughout the day.
• Lose weight if you are overweight.
• Whenever possible, do not remain standing or sitting for more than one hour at a time, especially if you are traveling and your trip is longer than four hours.
• If you must remain seated for a long trip, change your sitting position as often as possible.
• If you cannot move around while sitting for long periods, point and flex your toes and make circles with your feet to circulate your blood.
• Reduce the amount of salt you consume in your diet.
• Avoid bumping, hurting, and crossing your legs.
• Do not place pillows under your knees.
• Use blocks or books to raise the bottom of your bed 4–6 inches.
• Take all over-the-counter and prescription.
• Follow advised self-care measures necessary to keep health issues like heart failure or diabetes as stable as possible.
• Discuss your risk of clotting if you are taking hormones for birth control or replacement therapy, or during and right after pregnancy.

Anticoagulants

If you have a high risk of developing a blood clot in your leg or have an existing one, your healthcare provider may prescribe an anticoagulant. These medications, also called blood thinners, work on your blood’s clotting factors to prevent new clots from forming and current clots from increasing in size. Anticoagulant treatment is the standard initial treatment for a leg blood clot.

There are several types of anticoagulants. Each type interferes with different clotting factors. Since all anticoagulants can cause too much bleeding, you must be closely monitored by a healthcare provider while taking these drugs.

The most common anticoagulants used to prevent or treat a blood clot in a leg include the following:

Intravenous (IV) and injectable anticoagulants:

Oral anticoagulants:

Contact a Healthcare Provider If You’re Unsure

Contact your healthcare provider if you’re unsure about symptoms that may indicate the presence of a blood clot in your leg. It can be hard to distinguish the leg pain of a blood clot from other conditions. Signs and symptoms of a blood clot in your leg can often be confused with a muscle injury, cellulitis (a bacterial skin infection), or inflammation.

If you have had recent surgery, it is important to follow your post-op instructions to reduce your risk of a blood clot in your leg. Your instructions may include the following guidelines:

• Elevating the foot of your bed
• Doing specific exercises such as ankle rotations and lifting your legs up and down several times daily
• Taking pain medication to allow for as much movement as possible
• Taking anticoagulant medication (blood thinners), in some cases
• Wearing compression stockings
• Wearing a sequential compression device or intermittent pneumatic compression device (plastic sleeves connected to a pump that applies gentle pressure to your legs to promote blood flow)

Do not delay if you experience the following symptoms of a pulmonary embolism. This is a life-threatening condition. Call 911 or get immediate emergency care if you have any of the following symptoms:

• Sudden, unexplained shortness of breath
• Chest pain that worsens when breathing in, causing the feeling that you are having a heart attack
• Dizziness, lightheadedness, or syncope (loss of consciousness)
• Cough with or without blood
• Leg pain or swelling
• Pain in your back
• Excessive sweating
• Blueish lips or nails

Summary

A blood clot in your leg is a serious problem. Knowing the signs of a blood clot in your leg can help you get a prompt diagnosis and begin treatment early. Do not dismiss leg pain or swelling if you have risk factors for a blood clot in the leg.

The right treatment can help prevent the clot from growing. It can also reduce the risk of a piece of the clot breaking off and blocking the blood flow to your lungs. If the blood clot remains intact, treatment can help avoid long-term damage to the veins in your legs.

If you are at risk of a blood clot in your leg, consult your healthcare provider for any leg or calf pain. Get emergency care if you have symptoms of a pulmonary embolism, which can be fatal if left untreated.