Why Are There Blood Clots In My Urine?

Seeing blood in your urine is alarming. Seeing an actual clot makes it worse. A blood clot in your urine means you are bleeding somewhere in your urinary tract — the kidneys, ureters, bladder, or urethra — and the blood has pooled and clotted before leaving your body. This is not normal, and it always deserves a medical evaluation. The cause can range from a simple urinary tract infection to a kidney stone to something more serious, and only a doctor can determine which one it is.

What Does a Blood Clot in Urine Actually Mean?

A blood clot forms when blood proteins and platelets stick together to stop bleeding. In the urinary tract, this happens when bleeding is heavy enough or slow enough that the blood has time to coagulate before you urinate. The clot itself is not the disease — it is a sign that active bleeding is happening somewhere in your system.

The shape of a clot can offer clues. Long, stringy, worm-like clots often come from the kidney or ureter. These structures are tubular, so blood that clots inside them takes on that shape. Round or irregular clots are more common when the bleeding is in the bladder. This distinction is useful for your doctor, but it is not a diagnosis on its own.

Blood in urine — called hematuria — can be visible to the naked eye or only detectable under a microscope. When you can see it, doctors call it gross hematuria. When you cannot see it, it is microscopic hematuria. Clots only occur with gross hematuria because you need a meaningful amount of blood for clotting to happen.

What Are the Most Common Causes?

Several conditions can cause blood clots in urine. Some are common and easily treated. Others are serious and require prompt attention.

Urinary tract infections (UTIs) are the most frequent cause. The infection irritates the lining of the bladder or urethra, causing inflammation and bleeding. This is especially common in women. You will often have other symptoms like burning during urination, frequent urges to urinate, and pelvic discomfort. The bleeding usually resolves once the infection is treated with antibiotics.

Kidney stones are another leading cause. Stones scrape the delicate lining of the kidney, ureter, or bladder as they move. This can cause significant bleeding, sometimes with clots. The pain is typically severe and comes in waves, though some people pass stones with minimal discomfort. Blood may appear during the passage or after the stone has moved.

Enlarged prostate affects men, typically those over 50. The prostate surrounds the urethra, and when it enlarges, it can compress the urinary tract. The veins on the surface of an enlarged prostate are fragile and can bleed, especially after urination or ejaculation. This is not cancer, but it can cause visible blood and clots.

Kidney disease can also cause bleeding. Glomerulonephritis — inflammation of the kidney’s filtering units — can allow blood cells to leak into the urine. Some forms of this disease are mild, while others can progress to kidney failure. Blood pressure medication and other treatments are often needed.

Trauma is a straightforward cause. A blow to the kidney area, a fall, or a surgical procedure on the urinary tract can cause bleeding that clots. If you have had recent surgery, a procedure, or an injury, that is likely the explanation.

When Could Blood Clots in Urine Be a Sign of Cancer?

This is the question most people worry about, and it deserves a direct answer. Cancer of the bladder, kidney, or prostate can cause blood in the urine. Bladder cancer is the most common of these, and visible blood in the urine is often its first — and sometimes only — symptom.

Bladder cancer is more common in men than women, and smoking is the biggest risk factor. Exposure to certain industrial chemicals also raises the risk. The bleeding is often painless and can come and go. This intermittent pattern is dangerous because people assume the problem resolved when the blood disappears. It has not. The cancer is still there.

Kidney cancer can also cause blood in the urine, though it is less common than bladder cancer. Prostate cancer rarely causes visible blood in urine unless it has grown significantly. If you are over 40, a smoker, or have a family history of these cancers, your doctor will take blood in the urine very seriously.

Do not assume the worst, but do not dismiss it either. The only way to rule out cancer is through testing — imaging, urine analysis, and possibly a cystoscopy, where a thin camera looks inside the bladder. These tests are straightforward and can give you a definitive answer.

What Other Conditions Can Cause This?

Beyond the common causes, several other conditions can lead to blood clots in the urine.

Medications can be responsible. Blood thinners like warfarin, apixaban, and rivaroxaban increase bleeding risk. Aspirin and other anti-inflammatory drugs can also irritate the stomach and kidneys. If you take any of these, your doctor will want to know. Sometimes the dose needs adjustment, but never stop a blood thinner without medical supervision — that carries its own serious risks.

Exercise-induced hematuria is a real but less common cause. Intense exercise, especially running, can cause minor bleeding in the bladder wall. This usually resolves within 24 to 48 hours of rest. If the blood persists beyond that, another cause should be sought.

Inherited conditions like sickle cell disease or Alport syndrome can cause blood in the urine. These are less common but relevant if you have a family history. Polycystic kidney disease — where fluid-filled cysts grow in the kidneys — can also bleed, sometimes heavily.

Recent procedures are another cause. A biopsy of the kidney, a stent placed in the ureter, or surgery on the prostate can all cause bleeding that lasts for days. Your doctor should have told you to expect this. If the bleeding worsens or does not settle, call them.

When Should I Go to the Emergency Room?

Some situations require urgent care. Do not wait for an office appointment if you have any of the following:

• You cannot urinate at all, or you are passing only small amounts of blood
• You have large clots that are difficult to pass
• You have severe pain in your back, side, or abdomen
• You have a fever, chills, or nausea along with the blood
• You feel dizzy, lightheaded, or faint
• You have recently had surgery or trauma to the urinary tract

These symptoms can indicate a blocked urinary tract, a severe infection, or significant blood loss. All of these need immediate attention. A clot can physically block the flow of urine from the kidney, causing pressure to build up. This is called urinary obstruction, and it can damage the kidney if not relieved quickly.

If the bleeding is light and you have no other symptoms, you can usually wait to see your regular doctor — but see them soon. Within a day or two, not weeks. Blood in the urine is never something to monitor at home indefinitely.

How Will My Doctor Figure Out the Cause?

Your doctor will start with a detailed history and a physical exam. They will ask about your medications, recent activities, any pain, and your family history. Then they will order tests.

A urinalysis is always first. It checks for blood, protein, infection, and other abnormalities. A urine culture can identify specific bacteria if an infection is present.

Blood tests check your kidney function. They measure creatinine and estimate your glomerular filtration rate (GFR). These numbers tell your doctor how well your kidneys are filtering waste. They also check for anemia, which can develop if you have been bleeding for a while.

Imaging is almost always part of the workup. A CT scan without contrast is the most common test for blood in the urine. It can see kidney stones, tumors, cysts, and structural abnormalities. Ultrasound is another option, especially for people who should avoid radiation, like pregnant women, though it is less detailed than a CT scan.

Cystoscopy is the test that looks directly inside your bladder. A thin tube with a camera is passed through the urethra. It is done in the office with local anesthetic. It is the most reliable way to see bladder tumors, inflammation, or other problems in the bladder lining.

Not everyone needs every test. Your doctor will tailor the workup based on your age, symptoms, and risk factors. But if you have visible blood in your urine, expect a thorough evaluation. This is one situation where being thorough is the right approach.