Blood is meant to flow smoothly through your body. When you get a cut, your blood forms a clot to stop the bleeding. That is a good thing. It is how your body heals.
Sometimes a clot forms inside a vein when it is not needed. This can happen when blood flows too slowly, when a vein is damaged, or when your blood is more likely to clot than normal. The clot can block the vein and cause pain and swelling.
The legs are the most common place for these clots. Blood in your legs has to travel uphill against gravity to get back to your heart. That makes it easier for blood to slow down and clump together.
Not all leg clots are the same. Doctors sort them into two main types, based on which veins they form in.
Superficial vein clots form in veins close to the surface of your skin. You can sometimes see or feel them. The area may look red, feel warm, and hurt when you touch it. It may feel like a hard, tender cord under the skin.
Deep vein thrombosis (DVT) forms in the larger veins deep inside the muscles, most often in the calf or thigh. "Thrombosis" is the medical word for a clot forming in a blood vessel.
The line between the two is not always clear. A superficial clot can grow and reach a deep vein. In some studies, a meaningful number of people with a superficial clot were also found to have a DVT at the same time. That is why doctors often use an ultrasound to check, even when a clot looks minor. They want to know exactly what they are dealing with.
The biggest danger of a DVT is not the clot in the leg itself. It is what can happen next. A piece of the clot can break off and travel through the bloodstream. If it reaches the lungs, it can block blood flow there. This is called a pulmonary embolism, or PE. A PE can cause serious damage and can be life-threatening.
The Centers for Disease Control and Prevention (CDC) estimates that up to 900,000 people in the United States are affected each year by DVT or PE. Many of these cases can be prevented or treated if they are caught in time.
Anyone can get a blood clot. But some things make it more likely:
- Recent surgery or a hospital stay
- Sitting or lying still for a long time, such as on a long flight or car ride, or while on bed rest
- An injury to a leg
- Cancer or cancer treatment
- Pregnancy and the weeks after giving birth
- Birth control pills or hormone therapy that contain estrogen
- Being overweight
- Smoking
- Older age
- A family history of blood clots, or an inherited clotting condition
A common myth is that only older or inactive people get clots. That is not true. Young, healthy, active people can get them too. Athletes are a good example. A hard hit to the leg can damage a vein. Long travel to games, dehydration, and intense training can also play a role. Some athletes who use their arms a lot, such as swimmers and basketball players, can even get clots in the shoulder or arm.
Having a risk factor does not mean you will get a clot. It just means you should pay closer attention to the warning signs.
Signs of a clot in the leg:
- Swelling in one leg, usually the calf or thigh
- Pain or tenderness, which may feel like a cramp or a deep soreness
- Skin that feels warm to the touch
- Red or discolored skin
The key word is one. A clot usually affects only one leg. If both legs swell at the same time, it is often caused by something else, but you should still get it checked.
Signs of a clot in the lungs (call 911 or go to the ER right away):
- Sudden shortness of breath
- Sharp chest pain, especially when you breathe in
- A fast heartbeat
- Coughing, sometimes with blood
- Feeling dizzy, lightheaded, or faint
Do not wait to see if these symptoms go away. A pulmonary embolism is an emergency.
Some clots cause no symptoms at all. This is one reason they can be so tricky. A person can have a DVT and feel fine, or think they just have a sore muscle. Many people only learn about a clot after it causes a bigger problem.
If a doctor thinks you might have a clot, here is what usually happens. The doctor will ask about your symptoms, recent injuries, surgeries, travel, medicines, and family history. They will look at your leg. Many doctors use a scoring system to estimate how likely a clot is.
D-dimer Blood Test
D-dimer is a substance your body makes when a clot breaks down. A low result can help rule out a clot in people who are at low risk. A high result does not prove you have one, because many other things can raise it. It just means more testing is needed.
This is the main test for finding a DVT. A technician moves a small handheld device over your leg. It uses sound waves to make a picture of the blood flowing in your veins. It does not hurt, it does not use radiation, and it usually takes less than an hour.
Other Scans, If Needed
In some cases, doctors use a CT scan or an MRI to get a better look. These are not used as often for leg clots.
The ultrasound can show where the clot is, how big it is, and whether it is superficial or deep. That information decides what treatment you will need.
This is a common question. When a pro athlete gets a scan, it can seem like a special benefit that regular people do not get. The truth is simpler.
Yes, regular people can get a leg ultrasound. It is a routine test. It is available at hospitals, emergency rooms, many urgent care centers, and outpatient imaging centers. You do not need to be an athlete or have special connections.
The real difference is what leads to the scan. For most people with insurance, a scan is covered when it is medically necessary. That usually means you have symptoms, like a swollen and painful leg, or a risk factor, like a recent surgery. A doctor orders the test, and your insurance reviews it.
What is not usually done is scanning healthy people who have no symptoms. Doctors do not routinely screen the general public for clots. For most people, the test would not help, and it could lead to extra worry and unneeded treatment. Sports teams are different. They have medical staff on site. They can order scans quickly, and they can choose to scan "just to be safe." Most of us do not have that kind of access.
So how do regular people usually find out they have a clot? Most often it happens in one of three ways:
- Symptoms lead to a doctor visit. Leg swelling or pain sends someone to their doctor or an urgent care.
- A hospital stay. Patients who have had surgery or are on bed rest are watched closely for clots.
- An accidental discovery. Sometimes a clot is found by chance during a scan ordered for another reason.
- Be specific with your doctor. Say things like "My left calf has been swollen and sore for two days," or "I just got back from a long flight."
- Mention any risk factors, even if they seem unrelated.
- If you have chest pain or trouble breathing, go to the ER. Do not wait for an appointment.
- Costs and coverage are different for every plan. Call your insurance company or ask the provider's billing office before the test if the situation is not an emergency.
What Happens When a Clot Is Found? Treatment depends mostly on whether the clot is superficial or deep.
The main treatment is anticoagulant medicine, often called a blood thinner. The name is a little misleading. These drugs do not actually thin your blood. They make it harder for new clots to form and keep the current clot from growing. Over time, your body breaks the clot down on its own.
Most people take blood thinners for at least three months. Some people need them longer, depending on what caused the clot and how likely it is to come back. Many of these medicines come as pills, so most people can treat a DVT at home.
Blood thinners work well, but they come with a risk. They make it easier to bleed. Your doctor will go over what to watch for and which activities to avoid. For example, people on blood thinners are usually told to avoid contact sports. This is one reason clots can keep athletes out of games for weeks or months.
In rare, serious cases, doctors may use stronger treatments. These include medicines that dissolve clots, procedures that remove the clot, or a small filter placed in a large vein to catch clots before they reach the lungs.
Smaller superficial clots are often treated at home. Doctors may suggest:
- Warm compresses on the area
- Anti-inflammatory pain medicine, like ibuprofen, if it is safe for you
- Compression socks
- Staying active and walking, instead of resting for long periods
Blood thinners are sometimes used too. A doctor is more likely to suggest them if the clot is large or close to a deep vein. Because a superficial clot can sometimes move or grow, doctors often schedule a follow-up ultrasound to make sure it is not getting worse.
You cannot prevent every clot. But these steps can help:
- Move. Walk around every hour or two on long flights or car trips. Flex and stretch your ankles and calves while seated.
- Stay hydrated. Drink water, especially when you travel.
- Follow your care team's advice after surgery. This may include getting up and walking soon after, wearing compression devices, or taking medicine to prevent clots.
- Do not smoke.
- Keep a healthy weight.
- Talk to your doctor if you have a family history. This is especially important before surgery, pregnancy, or starting hormone-based medicine.
- Myth: Only older, inactive people get blood clots. Fact: People of any age and fitness level can get them.
- Myth: A clot always hurts. Fact: Some clots cause no symptoms.
- Myth: You can just walk off any clot. Fact: Movement helps with some superficial clots, but a suspected DVT needs medical care. Do not massage a sore, swollen leg that might have a clot.
- Myth: Blood thinners make your blood thin like water. Fact: They lower your blood's ability to clot. They do not change its thickness.
