Blood Clot in Leg (DVT/Deep Vein Thrombosis) Symptoms, Tests, Diagnosis and Treatment

Blood clots are clumps of blood that have changed from a liquid to a solid state. Normally, blood clots are good. For example, when you get a wound, a blood clot will form a scab at the location of the lesion. This stops the bleeding. However, when blood clots form in the veins of your body (called a thrombus) it can be very dangerous.

Blood clot leg

When a blood clot forms in your calf/thigh/groin area, the clot is called a Deep Vein Thrombosis or a DVT. This type of clot can interfere with blood flow and causes serious health conditions such as a Pulmonary Embolism - which is when the blood clot travels to your lungs and blocks the pulmonary artery and prevents oxygenated blood to flow to your lung.

Blood Clot Calculator (DVT Calculator)

You can use this if you're asking yourself "do I have a blood clot in my leg?" or "do I have a DVT?"

When someone is suspected to have a blood clot in their leg (DVT), a doctor will ask a set of questions to determine the chance of a DVT and what tests to perform next. These questions are based on the Wells Score for a DVT, which is what this Blood Clot Calculator uses.

This Blood Clot Calculator is what doctors use to initially diagnose you to figure out what tests to do next. Use it yourself by clicking below.


Question 1 of 10

1. Did you recently get treatment for cancer (last 6 months) or are currently being treated for cancer?

Question 2 of 10

2. Have you experienced paralysis or partial loss of voluntary movement of your lower extremities? Or have you had a recent cast that left you unable to move your lower extremities?

Question 3 of 10

3. Have you been bedridden recently for more than 3 days, had major surgery within twelve weeks?

Question 4 of 10

4. Is your calf swelling more than 3 cm compared to the other leg?

Question 5 of 10

5. Is there a certain part of your calf/thigh/groin (deep venous system) that feels more tender than the rest of your leg?

Question 6 of 10

6. Is your entire leg swelling?

Question 7 of 10

7. When you apply pressure to the swollen area with your finger and then release it, does it cause an indentation that lasts for some time? (this is called a pitting edema)?

Question 8 of 10

8. Do you have visible surface veins that are not varicose?

Question 9 of 10

9. Have you had a blood clot in your leg before (prior DVT)?

Question 10 of 10

10. Is there an alternative cause for the symptoms you have that is considered at least as likely as a DVT?


Start Over

Disclaimer: The following test is provided as an information resource only and is not to be relied on or substituted for any professional diagnostic or treatment. If you beleive you have a blood clot, you must consult a doctor.

DVT Symptoms and Causes

If you have any of the symptoms below then call your doctor right away so that your doctor can perform DVT tests and a DVT diagnosis to determine if you have a DVT.

If any of the below causes fit you, then you are inherently more susceptible to dangerous blood clots than other people.

DVT Symptoms

  • Swelling in one or both legs
  • Pain/tenderness/cramping in one or both legs, which may occur only while standing/walking or flexing your foot downwards/upwards
  • Warmth in the skin of the affected leg
  • Red or discolored skin in the affected leg
  • Visible surface veins (non-varicose)
  • Leg fatigue

DVT Causes

  • You have recently been on a long plane rides in a cramped space
  • You are in a cast that leaves parts of your lower body immobile
  • You sit for long periods of time without moving your legs
  • You are smoking
  • You are taking birth control pills, hormone therapy, an estrogen altering drug
  • You are taking steroids
  • You are pregnant
  • You are overweight
  • You are over 60
  • You have had a "central line" catheter inserted in your vein
Did you know that you can keep track of your blood clot related symptoms by signing up for a free account at INR Tracker. Learn more or .

Diseases That Cause DVTs

DVT Diagnosis Tests

When diagnosing for a DVT your doctor will do a physical and go through your health, medical history, and symptoms. Additionally, you will be asked the questions in the above DVT Calculator to get your Wells Score.

Because DVT symptoms are shared by other conditions, the doctor will need to do one or a few tests to rule out other problems. These tests include blood tests (such as a d-Dimer), a Duplex Ultrasound Test, a Venogram Test and an MRI Test (Magnetic resonance imaging).

DVT Blood Tests

Dr. Oller, an emergency physician, talks about the d-Dimer Blood Test.

A d-Dimer Test is a blood test that helps rule out an active blood clot. If it comes back negative, then it nearly rules out the possibility that you have an actively forming blood clot. But, if you have a positive result (an elevated d-Dimer Test Result) that means that you need a Duplex Ultrasound Test.

Other blood tests should be ordered after the full diagnosis is done to see if you have any of the diseases mentioned above in this article. For example, Factor V Leiden, a clotting disorder, affects over 10 million Americans and can be confirmed with a blood test and additionally with a genetic test.

Duplex Ultrasound Test for DVTs

Duplex ultrasound

This is what part of the Duplex Ultrasound Test looks like. 12

The Duplex Ultrasound Test is considered the primary way of diagnosing a DVT and requires a very skilled radiologist or sonographer to make sure the results are accurate.

This test has a two part process and that's why it has "duplex" in its name. It is painless, require no radiation and is noninvasive, which means nothing goes inside of your body.

First Part of the Duplex Ultrasound Test

In the first part of the process, your internal tissues, specifically your veins are targeted for imaging. This part uses an ultrasound called brightness modulation ultrasound, also known as B-mode Ultrasound.

The radiologist or sonographer will spread warm gel on your skin and then will move an ultrasound wave around the area. This wand is what sends the sound waves through your body and sends the waves that bounce back to a computer. The computer interprets the sounds as an image.

While the wand is moving around, the specialist will try to compress the veins. If the vein cannot be compressed because a clot is preventing it, then a DVT diagnosis is made.

The ability to completely flatten a vein with compression is an effective way of being certain that a clot is not present in the vein.

Second Part of the Duplex Ultrasound Test

In the second part of the process, your blood flow is targeted for imaging. This part uses an ultrasound called Doppler Ultrasound.

The specialist looks for abnormalities in your blood flow. The specialist waves the wand around an area and the wand sends sound waves that bounce off the blood inside of veins to the computer.

If there is something abnormal about the blood flow confirms the diagnosis of a DVT.

Success Rate of the Duplex Ultrasound Test

It is generally considered that the Duplex Ultrasound Test is great for diagnosing clots in large veins above the knee (95% sensitivity 11) but only moderately effective for diagnosing clots below the knee (73.55% sensitivity 11).

If the Duplex Ultrasound Test comes back negative, but a DVT is still suspected because it might be in the pelvis then a Venogram Test (Venography Test) is given. The Venogram Test most likely given is an MRI Test.

Venography Tests for DVTs

There are two types of Venography Tests. One that involves x-rays and one that involves a MRI. An MRI is preferred because it is painless. MRI Venography Tests do a better job than Duplex Ultrasound Tests for the Pelvis, Abdomen, and Chest because it doesn't use compression.

The X-ray Venography Test

The X-ray Venography Test is not often done because it is painful and has additional clotting risks. The test involves injecting a dye into the veins of the foot and then taking an x-ray of the veins in the leg to see where there was a blockage. In other words, where the clot is located.

The dye causes discomfort when injected and in some cases may even stimulate the blood to clot. That is why a Venography Test is usually used only in clinical studies or when an ultrasound result is uncertain.

MRI Venography Tests for DVTs

This test is effective in finding a DVT in your pelvis as well as in your thigh. It also allows your Doctor to see both of your legs at once. However, MRI Tests are often a last resort for DVT diagnosis because they are much more expensive than the other tests.

MRI uses radio waves and a magnetic field to create images of your body. When getting an MRI you lie still on a sliding table and you'll hear loud noises that sound like knocking or tapping.

DVT Diagnosis Algorithm 11

A DVT Diagnosis Algorithm is also called the Pretest Probability Assesment of a DVT.

This algorithm is not used for pregnant patients because the d-Dimer test gives a false positive.

  1. The doctor will use the DVT Calculator above to get your Wells Score.
  2. If the score is less than 2 then a d-Dimer blood test is taken.
    • If the d-Dimer test comes back negative, then a DVT is excluded, and the doctor will look for other reasons for your symptoms.
    • If the d-Dimer test comes back positive, then a Duplex Ultrasound is given to you.
  3. If the score is 2 or greater then a Duplex Ultrasound Test is given to you.
  4. If the Duplex Ultrasound Test is negative then a d-Dimer test is given to you and if given a negative result then a DVT is excluded. If positive, then a Venography Test will be given or this process will be repeated at a follow-up visit in 6 to 8 days.
  5. If the Duplex Ultrasound Test is positive then the DVT diagnosis is made and is treated.

DVT Treatment

The Goals of Treating a DVT

  • Make sure the clot does not grow
  • Make sure the clot does not break off, travel to the lung and cause a Pulmonary Embolism
  • Stop the swelling and pain in the legs
  • Prevent more blood clots from happening

Blood Thinner Therapy for a DVT

Blood Thinners Don't Actually Thin Your Blood

Treatment for a DVT is often a blood thinner therapy. Despite the name, blood thinners don't thin the blood, they just block the clotting factors that let your blood clot. Blood thinning therapy is called anticoagulation, and blood thinners are called anticoagulants.

It's also important to note that blood thinners themselves do not dissolve your clots.

Blood thinners keep a clot from growing or breaking off and prevents new clots from forming. This allows your body to dissolve the clot without worrying about new clots forming or the clot dislodging and getting stuck somewhere else.

Different Types of Blood Thinners

The main types of anticoagulants used to treat DVTs are Heparin, Low Molecular Weight Heparin (Lovenox), Warfarin (Coumadin), Dabigatran (Pradaxa), Apixaban (Eliquis) and Rivaroxaban (Xarelto).

Warfarin as a Blood Thinner Therapy

Warfarin is the most prescribed anticoagulant in the world and is taken orally. Initially when you start a Warfarin Therapy it is paired with either Heparin or a Low Molecular Weight Heparin (LMWH). This is because, Warfarin initially takes several days to reach its therapeutic effect. Once that happens, Warfarin stays in your system for several days, which makes it a good anticoagulant. Heparin or an LMWH are injected and work instantly. That's why one of them is initially paired with Warfarin. Additionally, when Warfarin is started, it may promote clot formation temporarily, and the Heparin/LMWH counteract that. Heparin/LMWH are extremely expensive drugs, and that's their downside.

LMWH (Low Molecular Weight Heparin) is as good if not better than standard Heparin, more convenient to use, has fewer side effects than standard Heparin, and requires less shots, because it lasts longer in the body than standard Heparin. LMWH doesn't have to be injected into a vein like standard Heparin does, it can be injected into the abdomen instead. With LMWH, one does not need to be in the hospital to use it. However, with standard Heparin, one needs to be monitored in a hospital. Lovenox and Innohep are approved LMWHs for the treatment of a DVT or Pulmonary Embolism.

Warfarin is effective, but it has shortcomings. Many medications interact with it as well as foods. In foods, particularly Vitamin K interacts with Warfarin. Also, one has to get blood tests to make sure that their Warfarin dosage is correct called the international normalized ratio test or better known as an INR Test.

Other Blood Thinners Vs Warfarin

Blood thinners like Pradaxa, Xarelto and Eliquis are easier to manage because they don't require blood tests or diet changes. but they have risks of internal bleeding, and there is no reversal. So if you have an internal bleeding episode, there's no way to stop it. In addition, these drugs are much more expensive than Warfarin. Warfarin is cheaper and in the event of an internal bleeding episode, Warfarin can be reversed.

Elevating Your Legs and Wearing Compression Stockings

Keeping your legs elevated can reduce the swelling and pain symptoms of a DVT. Putting books under the front legs of your bed can keep your bed elevated.

You should also wear compression stockings to prevent another clot from occurring. Compression Stockings go from the arch of your foot to just above or below your knee.

Keep track of your Vitamin K, Warfarin Therapy, and INRs here on INR Tracker for Free. Learn more or .

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