Blood Clots in Urine – Causes of Urinary Clotting

Blood is not a usual component of urine. Detection of blood in the urine is abnormal, and is technically known as hematuria. It is usually an indication that there is bleeding somewhere in the urinary system. However, not all cases of blood in urine are due to serious causes. In most cases, blood in the urine is not even visible. This is because a small amount of blood is diluted within a large volume of urine.

In these cases, only laboratory tests on urine samples may reveal the presence of blood cells. In other cases, blood in urine may be clearly seen with the naked eyes. In very rare instances, urine may turn red due to the presence of large amounts of blood in it. Blood in the urine may or may not be associated with other signs and symptoms. Pain is a common accompanying symptom. However, absence of pain does not mean that the underlying cause is not serious. Any detection of blood in urine should be taken seriously and prompt medical attention must be sought.

Clotted Blood

Sometimes, urine may also contain blood clots. A blood clot is a mass of blood cells and other components of the clotting cascade. Blood clots form at sites of blood vessel injury. It plugs the damaged sites on the walls of injured blood vessels, thereby preventing blood loss through leakage. Sometimes, these clots get dislodged from the walls of blood vessels and travel through blood stream.

These wandering clots pose a serious health risk if they get stuck in the narrow blood vessels of circulatory system. Blood clots also form when blood leaks out of the confines of a blood vessel. This is because the factors that prevent clotting of blood are present only within the blood vessels. A failure of these clotting mechanisms within the blood vessels could also lead to clot formation within undamaged blood vessels.

Blood clots are semi-solid in consistency. Therefore, it may cause pain as they pass through the urinary tract. A large clot may also block the flow of urine completely. The presence of a large clot in the urine suggests a large amount of bleeding, usually in the upper regions of the urinary system. However, clots can also result from even small amounts of bleeding.

Causes of Blood Clots in Urine

Blood clots in urine could arise from bleeding occurring in any region of kidney, bladder and urinary tract. It is also possible that blood in urine may not actually be from the urinary tract. It may be due to bleeding at the tip of genitals. Since urine flows in close proximity to the genitals, blood from the genitals may be mixed in the urine.

Dietary factors

The foods and drinks we consume contribute to the color of the urine. Some foods or drinks may cause a reddish discoloration of urine. This discoloration may be mistaken for blood in urine. However, some foods do increase the chances of bleeding in the kidneys and the urinary tract. These foods have ingredients that act as natural blood thinners. Examples include berries, beets, rhubarb, and certain energy drinks.


Use of certain medicinal drugs and supplements is also associated with blood clots in urine. Examples of prescription medicines that increase the risk of blood in urine include non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, anti-hypersensitivity drugs, anti-epilpetic drugs, anti-histamines, anticoagulants, anti-retrovirals and anti-psychotics. Using high dosages of vitamin and mineral supplements can also cause blood in urine. Use of certain herbal remedies may also result in blood in urine.


Heavy metal poisoning may result in blood clots in urine. Toxicity caused by overdose of certain drugs (such as acetaminophen) is also associated with blood in urine.


One of the most common causes of blood in urine is urinary tract infection (abbreviated as UTI). There are a number of different bacteria that can cause urinary tract infections. Most cases of urinary tract infections are caused by ascending bacterial infections. The causative bacteria gains entry into the urinary system through the urethral opening and then ascends up the urinary tract.

Most cases of urinary tract infections are restricted to the bladder. In some cases, the bacterial infection may even reach the kidneys. Besides the urethral route, bacteria can also gain access to the urinary system through the bloodstream, which is filtered by the kidneys to produce urine. Rectum is another important source of bacteria that can cause urinary tract infections. Urinary tract infections can also be a result of sexually transmitted diseases.

Also read on urinary tract infection.

Kidney and bladder stones

Stones in kidneys and bladder can form upon precipitation of certain minerals present in urine. This is most likely to happen when a person is chronically dehydrated, and passes concentrated urine. Most kidney stones are very small, and do not cause any symptoms. It easily passes out through the urine. However, large stones could obstruct the flow of urine and cause severe pain. Stones from kidneys may travel through ureter and enter urinary bladder. If these stones are not passed out, they grow in size.

Also read on kidney stones.


A physical blow to abdominal region can injure kidneys, which are located in the mid-back region. This may cause bleeding from the kidneys and blood clots in urine. Kidneys can get injured with blunt trauma. Penetration of the organ with a sharp object is not necessary to cause bleeding.

Diseases of urinary tract

Various diseases of urinary tract can cause blood and blood clots in urine. Examples of such diseases include glomerulonephritis (post-infectious and membranoproliferative), immunoglobulin A nephropathy, lupus nephritis, urolithiasis, hydronephrosis, hyperuricosuria, and polycystic kidney disease.

Systemic diseases

Some systemic diseases could also cause blood clots in urine. Examples include Alport syndrome and sickle cell disease.


Blood in urine may also be caused by cancers of urinary system. Malignant cancers affecting urinary bladder, ureter and kidneys, can all cause blood clots in urine. In the initial stages of cancer, the amount of blood may be too small to be visible in urine. However, blood in urine may become visible as the cancer advances and invades blood vessels.

Prostate Diseases

Diseases of prostate gland in males may also be associated with blood clots in urine. Since urethra runs through prostate gland, bleeding from prostate may become visible in urine. Some examples of diseases that can cause hematuria include benign prostatic hyperplasia, infectious prostatitis, and prostate cancer.

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