713-489-6319 HOUSTON
469-214-5251 DALLAS
713-489-6319 HOUSTON
469-214-5251 DALLAS
This article was medically authored by Dr. Ryan Armstrong and last reviewed for accuracy on 08/06/2026.
Sometimes, blood clots form without giving you any warning. But sometimes, your body sends you blood clot signs that mean you’re heading for trouble. And we want you to identify them easily, so you can seek quick care if any develop.
For NBC anchorman Al Roker, who was hospitalized for a DVT near the end of 2022, recognizing these warning signs was life-saving. In fact, he developed one of the potentially-fatal DVT complications that make this type of clot a medical emergency. As he said, "I was admitted to the hospital with a blood clot in my leg which sent some clots into my lungs. After some medical whack-a-mole, I am so fortunate to be getting terrific medical care and on the way to recovery. Thanks for all the well wishes and prayers and hope to see you soon."
But what is a DVT, what other types of blood clots can develop, and how can you know when one is forming? read on to find out more!
A blood clot forms when some of the blood in your vessels becomes a solid mass. You can develop a clot in your arteries, which carry blood from your heart to your body. They can also form in veins, which carry blood from your extremities back to your heart. Or you can form a clot in your capillaries, whose job is to connect your veins and arteries.
Still, blood clots are most likely to form in your deep leg veins. (We call this clot a deep vein thrombosis or DVT.) Along with identifying blood clot signs, it’s very important to recognize DVT symptoms. Because, if this leg clot breaks free, it could travel to your lungs. There, it becomes a pulmonary embolism, which could be a fatal condition.
Now, in a minute, we'll tell you the symptoms of blood clots to watch out for. But first, you have to know where to look. And, for most people, the warning signs of blood clots will appear in the leg, thigh and ankle, so those are good places to monitor if you're concerned about clot formation.
When a blood clot is first forming, you may not have any visual or physical warning. In fact, the CDC estimates that about half of people with a DVT never notice a single symptom at all. But there are certain clear blood clot signs in your legs that you need to watch out for. And these are the blood clot symptoms our vein specialists want you to take seriously.
If you notice swelling in your leg, and it doesn’t go away when you put up your feet, that could be a warning of a forming clot. That’s especially true if the swelling lasts throughout the day, or if you notice additional signs of trouble. Pay close attention when the swelling shows up in just one leg, since simple fluid retention usually affects both legs about equally.
If your legs suddenly feel crampy, and you don’t have PAD, this new, nagging pain could be one of several DVT symptoms. Tenderness that gets worse when you stand or walk, and won't settle down after a day or two, deserves a call. So it’s worth mentioning to your vein specialist, especially if you already have varicose veins.
Watch your varicose veins carefully, as any of these changes could be blood clot signs. First, if your vein starts bulging more prominently, and won’t flatten out when you elevate your legs, you could be developing a superficial blood clot.
Other blood clots signs include veins that suddenly turn hard, or surrounding skin that turns red and feels tender to the touch.
Skin that feels noticeably warm over one spot on your calf or thigh is one of the blood clot symptoms people miss most often. The same goes for skin that turns red, bluish or unusually dark in one area. On its own, warmth may mean very little. Paired with swelling or new pain, though, it's a combination worth getting checked.
As we mentioned, you need to watch DVT symptoms carefully, because these clots can travel to your lungs. If you have a pulmonary embolism, your symptoms can include new or different shortness of breath—especially if it doesn’t go away with rest.
You may also experience lingering chest pain, or chest pain that develops when you breathe deeply. In extreme cases, you may even cough up significant amounts of blood if you have a blood clot in your chest.
For years, a clot in a surface vein was treated as a nuisance rather than a red flag. A tender, ropy, warm vein close to the skin (sometimes called superficial thrombophlebitis) hurt for a week or two, then faded.
The research says otherwise. And it's why we now tell patients that superficial blood clots may be a warning sign of something deeper.
In one large study of 844 people with a superficial leg clot, published in the Annals of Internal Medicine, nearly one in four already had a deep vein clot or a pulmonary embolism at the moment they were diagnosed. A later review pooling more than 4,300 patients found concurrent DVT in about 18% of cases and a pulmonary embolism in about 7%. Just as telling: among patients whose superficial clot appeared to be isolated at first, roughly one in ten went on to develop a deep clot, a PE or a spreading clot within three months. And that happened even though nine out of ten of them were already taking blood thinners.
At Texas Endovascular, our board-certified interventional radiologists use in-office duplex ultrasound to map exactly which veins are involved and how far the clot extends.
With eight vein clinics across Greater Houston and the Dallas–Fort Worth area, in Houston, Katy, Sugar Land, The Woodlands, Clear Lake, Dallas, Plano and Fort Worth, we can usually get you scanned close to home and quickly. Our team has spent more than 50 combined years caring for patients with vein disease, from spider veins to complex venous insufficiency and DVT.
If you think you have a pulmonary embolism, you should immediately go to the emergency room. There, you can get a quick CT scan and breathing tests, so we’ll know if you have a blood clot in your lungs. If the tests reveal a PE, treatment can begin right away.
Now, if you only have DVT symptoms, you can skip the ER. But you should schedule an immediate appointment with our vascular specialists, who see patients at eight locations across Greater Houston and the Dallas–Fort Worth area.
Studies show that early intervention is very important when we treat deep vein clots. It means compression therapy and other interventions may be more effective. So, the sooner you alert us to the problem, the sooner we can offer treatment and results. And, more importantly, the less likely you are to face life-threatening complications like a pulmonary embolism!
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