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Heart & Circulation

Blood Clot in the Leg: 4 Signs to Check, and Why Half of People Have No Symptoms

A deep vein clot has four signs worth knowing. About half of the people who get one have none of them, which is why the risk list matters as much.

Ageless Coach Editorial Team · September 19, 2026

In 30 Seconds
Half have no symptoms. The CDC says about half of people with deep vein thrombosis have no symptoms at all. CDC
Four signs are the short list. The CDC names swelling, pain or tenderness, warmth, and redness or discoloration in the affected leg or arm as the most common signs. CDC
A leg clot can reach the lungs. Mayo Clinic calls a pulmonary embolism a life threatening complication of deep vein thrombosis and says to seek emergency medical help if its signs appear. Mayo Clinic

A blood clot in a deep leg vein shows up four ways: swelling, pain or tenderness, warmth, and redness or a change in skin color.

The catch is that about half of the people who have one get no symptoms at all. That is why doctors lean on the risk list. It runs from recent surgery to long stretches of sitting to being over 60.

Below are the four signs and the risk factors that put you on that list. Then the emergency symptoms that mean call 911 rather than book a visit. That last group is the one to memorize.

1
The short list · Signs

Four signs of a clot in the leg, and where they turn up

The signs are local. They show up in one leg, not both, and they build rather than flash.

The CDC lists four as the most common (CDC, 2026). Compare one leg against the other and the difference is usually what you notice first.

  1. Swelling in one leg. The CDC names swelling first. Mayo Clinic says deep vein thrombosis can cause leg swelling, and that a clot usually forms in the legs rather than anywhere else.
  2. Pain, cramping or soreness, often in the calf. The CDC lists pain or tenderness. Mayo Clinic is more specific and says the pain, cramping or soreness often starts in the calf.
  3. Warmth in the affected leg. The CDC lists warmth. Mayo Clinic describes a feeling of warmth on the affected leg, which is easiest to spot by touching both legs in turn.
  4. Redness or a change in skin color. The CDC lists redness or discoloration. Mayo Clinic says the change on the leg can look red or purple, depending on the color of your skin.
About half
The share of people with deep vein thrombosis who have no symptoms at all. The risk list does the work the symptoms cannot.
Source: CDC

Any one of the four in a single leg is worth a same day call. The CDC says to see your doctor as soon as possible if you have any of them.

2
The risk list · Who gets them

The risk factors that matter more than the symptoms do

Because half of these clots are silent, risk is the better signal.

Johns Hopkins Medicine names age over 60, surgery and a long period of not moving (Johns Hopkins Medicine, 2026). The list also holds a previous clot, pregnancy, cancer and some cancer treatments, hormone therapy, a clotting disorder and extra weight.

View of an aircraft wing and clouds through a passenger window seat
Long stretches of sitting are one risk factor among many. Johns Hopkins says to walk the aisles, or to stop about every hour if you are driving.

Two items on that list are inside your control on any given day: how long you sit still, and whether you get up.

Johns Hopkins says to walk the aisles on a plane or a bus. Stop about every hour to walk if you are driving. Move your legs, ankles and toes while seated, wear loose clothing, go easy on alcohol and drink plenty of water.

About half of people with DVT have no symptoms at all.

CDC

Know exactly what to say at your visit

Your free one page plan turns these four signs into three steps: what to check on your own leg, what to do every hour on a long trip, and the words to use with your provider.

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3
The emergency · Lungs

The symptoms that mean call 911 and not your doctor

A leg clot matters because it can move.

Mayo Clinic says a pulmonary embolism happens when a clot gets stuck in an artery in the lung. It blocks blood flow to part of the lung. Mayo calls it a life threatening complication of deep vein thrombosis (Mayo Clinic, 2026).

A man in a sun hat walking away from the camera along a grassy path
Getting up and moving is the plainest prevention on the Johns Hopkins page, both after surgery and on any long journey.
About 30%
The share of people who have had a clot in a leg or a lung who are at risk of another episode.
Source: CDC

Mayo Clinic lists the warning signs of a pulmonary embolism. Sudden shortness of breath. Chest pain that gets worse when you breathe deeply or cough. Feeling lightheaded or dizzy, fainting, a fast pulse, fast breathing, or coughing up blood.

It says to get immediate medical help if you have those symptoms. That is the one group on this page that does not wait for an appointment.

✗
What is not true

Three things people get wrong about leg clots

Three assumptions get in the way of catching these early.

A clot always hurts. It often does not. The CDC says about half of people with deep vein thrombosis have no symptoms at all, which is why the risk list carries as much weight as the symptom list.

Only long flights cause them. Sitting still is one risk factor among many. Johns Hopkins Medicine names surgery, age over 60, pregnancy, cancer and its treatments, a previous clot, hormone therapy and time spent immobile in hospital on the same list.

Once it is treated, it is over. Not always. The CDC says about 30% of people who have had a clot in a leg or a lung are at risk of another episode, and that one third to one half develop a long term complication called post thrombotic syndrome.

📋Your Coach's Recommendations
1
Compare one leg against the other tonight.
The CDC names swelling, pain or tenderness, warmth, and redness or discoloration as the four signs. Look at both legs together, because the difference between them is easier to see than either one alone.
2
Set an hourly reminder on any long trip.
Johns Hopkins Medicine says to walk up and down the aisles on a plane or bus, stop about every hour to walk if you are driving, and move your legs, ankles and toes while seated. Drink water and go easy on the alcohol.
3
Write your risk factors on one line before your next visit.
Johns Hopkins lists age over 60, recent surgery, long periods of not moving, a previous clot, hormone therapy, pregnancy and cancer treatment among them. Hand that line over rather than waiting to be asked.

To your health,

Ageless Coach

Age Strong. Live Long.

Trusted Sources Behind This Article
CDCMayo ClinicJohns Hopkins Medicine

This article is education, not medical advice. Mayo Clinic says to get immediate medical help if you have symptoms of a pulmonary embolism. Ageless Coach is an affiliate partner and may earn a commission on purchases made through links on this page.

Frequently Asked Questions

How do I know if my leg pain is a blood clot?
You cannot know for certain at home. The CDC names swelling, pain or tenderness, warmth, and redness or discoloration as the four common signs, and says to see your doctor as soon as possible if you have any of them. Mayo Clinic adds that the pain often starts in the calf.
Can I have a clot with no symptoms at all?
Yes, and it is common. The CDC says about half of people with deep vein thrombosis have no symptoms. Johns Hopkins Medicine says the same in its own words: deep vein thrombosis may happen without symptoms.
What should I do on a long flight or drive?
Johns Hopkins Medicine says to walk up and down the aisles on a plane or bus, stop about every hour to walk if you are driving, move your legs, ankles and toes while seated, wear loose clothing, limit alcohol and drink plenty of water.
When is a blood clot an emergency?
When it reaches the lungs. Mayo Clinic says to seek emergency medical help for sudden shortness of breath, chest pain that worsens on a deep breath or a cough, lightheadedness, fainting, a rapid pulse, rapid breathing or coughing up blood.
Does age put me at higher risk?
It is on the list. Johns Hopkins Medicine names age over 60 among the risk factors, alongside surgery, long periods of not moving, a previous clot, hormone therapy, pregnancy and cancer treatment.
Can I get another clot after the first one?
It happens. The CDC says about 30% of people who have had a clot in a leg or a lung are at risk of another episode, and that one third to one half go on to develop a long term complication called post thrombotic syndrome.
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