Blood Clots in Urine: What’s Behind Peeing Red

Updated 13 August 2021

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Reviewed by Andrei Marhol, PhD, Flo lead medical advisor, Lithuania

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The normal colors for urine may range from deep amber to pale yellow. Having red-colored urine or peeing blood clots is also known as hematuria. This condition may occasionally signal some serious health problems. Read on to learn more about blood clots in urine, their causes and consequences.

Can you always detect blood in your urine?

Hematuria is the presence of excessive blood in your urine. When blood in the urine is visible to the naked eye, it’s called macroscopic (visible) hematuria. On the other hand, sometimes blood in urine isn’t visible and is detected only in a laboratory examination when urine tests positive for the presence of blood. In such cases, it’s called invisible, microscopic, or non-visible hematuria. 

In certain cases, the presence of blood in urine may not produce any symptoms. That’s why it’s important to have regular exams, so that you don’t miss it.

Causes for peeing blood clots or having red-colored urine

On average, there are about one million red blood cells (RBCs) present in the urine of a healthy person every 24 hours. The presence of an excessive amount of RBCs in urine may occur due to a wide variety of pathological conditions of the urinary tract.  

Blood clots in urine may originate in any place in the urinary system — the urethra, bladder, or kidneys. The color of your urine may become cola-colored, red, or tea-colored.

Most common causes behind blood in the urine

Some of the most common causes of the presence of blood in the urine are:

Urinary tract infections (UTIs): A UTI occurs when bacteria enters the body by way of the urethra and grows in the urinary bladder. Apart from blood in urine, the other symptoms of a urinary tract infection are a constant urge to pass urine, urine with a very strong smell, and burning and pain while urinating.

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Pyelonephritis (kidney infection): Kidney infection occurs when bacteria travels to the kidneys from the lower urinary tract or gets into the kidneys from the blood. Symptoms and signs of pyelonephritis are usually similar to a UTI, though they may also cause flank pain and fever.

A kidney or bladder stone: If your urine is concentrated, then the minerals present in it may form crystals in the bladder or kidneys. Gradually, these crystals may form tiny, hard stones. They are usually painless unless they get passed or result in a blockage, when they may cause very severe pain along with both microscopic and macroscopic bleeding. They may lead to the occurrence of blood clots in urine.

Urinary tract and kidney infections, as well as bladder stones, are among the most common causes of blood in the urine.

Kidney disease: Blood in the urine may also occur due to an inflammatory kidney disease called glomerulonephritis. Vasculitis (diseases of the blood vessels), and immune system problems after strep or viral infections — for instance, IgA nephropathy that affects the glomeruli (small capillaries, which filter blood in your kidneys) — may trigger glomerulonephritis.

Cancer: Malignant diseases of the bladder or kidneys may also produce visible blood along with blood clots in urine.

Inherited disorders: Both invisible and visible blood in urine may occur due to sickle cell anemia, which is a hereditary red blood cell defect. Similarly, Alport syndrome, which affects the glomerular filtration membranes in your kidneys, may also cause the presence of blood in the urine.

Penicillin and the anti-cancer medicine cyclophosphamide may also result in urinary bleeding.

Injury to the kidney: A blow or any other type of injury to the kidneys from contact sports or an accident may cause the presence of visible blood as well as blood clots in urine.

Medicines: Penicillin and the anti-cancer medicine cyclophosphamide may result in urinary bleeding. Visible urinary bleeding may also sometimes occur after taking an anticoagulant.

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Some other reasons for red-colored urine

Apart from the causes mentioned above, some other reasons for red-colored urine are:

• Eating certain foods — beets, rhubarb, and blackberries may turn urine pink or red. Similarly, eating large quantities of fava beans or aloe may also make your urine dark brown.
• Taking certain medicines such as rifampin, sulfasalazine, phenazopyridine, and laxatives containing senna may also make the color of your urine red.
• Orange-colored urine may indicate that there is a problem in your bile ducts or liver, especially if light-colored stools accompany it.
• In rare instances, muscle injury due to strenuous exercise may lead to the occurrence of cola- or pink-colored urine.

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When to see a doctor

Blood clots in urine may indicate many serious health issues as already discussed, so they need immediate examination by a doctor in all cases. Furthermore, anyone with visible hematuria should also visit their doctor immediately to determine the cause.

You should get a medical evaluation even if:

• No other symptoms are present
• You saw blood in your urine only once
• Only a small quantity of blood is present in the urine
• You can’t tell for sure whether it is blood or not

Moreover, you should visit a doctor if you have the following symptoms along with blood in urine:

• Painful urination
• Fever
• Weight loss
• Reduced appetite
• Malaise and weakness
• Abdominal pain

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The takeaway

Though blood in urine can be harmless, it may signal potentially serious conditions such as a UTI, kidney infection, and more. Sometimes red-colored urine can be caused by foods, drugs, or exercise. 

Blood clots in urine aren’t commonly present and are a special type of hematuria. When present, though, they may indicate certain serious health issues such as bladder cancer, kidney injuries, and others.

If you see blood in your urine, it’s advisable to schedule an appointment with your doctor. It’s wise to do so even if you don’t have any other symptoms except for reddish pee. 

History of updates

Current version (13 August 2021)

Reviewed by Andrei Marhol, PhD, Flo lead medical advisor, Lithuania

Published (15 November 2019)