Causes of Blood in Urine

Although blood in the urine or hematuria can be alarming, it is not usually an indicator of a life-threatening condition. It can sometimes be related to a serious health issue.

If the blood is visible to the naked eye, the condition is referred to as “macroscopic,” “visible,” or “gross” hematuria. This should be investigated by a doctor. Sometimes, the blood can only be seen under a microscope. This is referred to as “microscopic” or “non-visible” hematuria. This should also be investigated because not even the smallest amount of blood should be present in healthy urine.

Blood seen in the urine arises from somewhere in the urinary tract, which is made up of the bladder, kidneys, ureters and urethra. Some of the most common causes are given below.

Reagent Strip for Urinalysis - Image Credit: Sirirat / Shutterstock
Image Credit: Sirirat / Shutterstock

Urinary Tract Infection

These infections often arise when bacteria migrate upwards through the urethra and start to proliferate in the bladder, causing cystitis. Signs of a urinary tract infection include a frequent urge to urinate, a pain and burning sensation when urinating and urine that has a stronger smell than usual.

Kidney Infection

Also called pyelonephritis, a kidney infection results when bacteria in the blood stream or ureters move into the kidney. This may lead to the same symptoms caused by urinary tract infection, although kidney infection may also cause a fever and abdominal pain.

Blood in the Urine: What does it mean?

Kidney or Bladder Stone

Minerals present in the urine sometimes form crystals in the lining of the kidney or bladder, which can eventually develop into stones. These do not usually cause pain, but they can lead to a blockage or may be passed in urine, which can be extremely painful and also lead to bleeding.


This term refers to inflammation of the urethra, the tube through which urine passes when it is eliminated from the body. It is often caused by a sexually transmitted disease such as chlamydia infection.

Enlarged Prostate

Also referred to as benign prostatic hyperplasia, this refers to the increase in size of the prostate in and after middle age. As the gland becomes bigger, it compresses the urethra, which can obstruct urine flow, making urination more difficult or slower, and leading to bleeding. Prostatitis (infection of the prostate) may also cause these symptoms.

Kidney Disease or Injury

Kidney disease often causes microscopic hematuria. The blood-filtering units of the kidney called glomeruli become inflamed. Examples of conditions that can cause kidney disease include diabetes, vasculitis, viral infection and certain immune disorders that affect the glomeruli. Accidents that result in injury to the kidney can also cause blood to be passed in the urine.

Kidney, Bladder or Prostate Cancer

Generally, all these cancers have a higher incidence in individuals aged 50 years and older. Aside form hematuria, other symptoms of urinary malignancies include the following:

Kidney cancer – an abdominal mass and persistent pain in the loin
Bladder cancer - more frequent and urgent need to urinate; pain on urination
Prostate cancer -  more frequent and urgent need to urinate; difficulty emptying the bladder

Inherited Disorders

Inherited conditions such as sickle cell anemia (due to defective hemoglobin in erythrocytes) and Alport syndrome (abnormality of the glomerular filtering membrane) can cause both macroscopic and microsopic hematuria.

Certain medications

Some drugs such as the antibiotic penicillin and the anticancer therapeutic cyclophosphamide can cause hematuria. If a person already has a condition that causes the bladder to bleed, then the use of anticoagulants such as aspirin or heparin may also lead to macroscopic hematuria.

Visiting the Doctor

A doctor will investigate the cause of hematuria by asking about the patient’s symptoms and carrying out a full physical examination. This may include a rectal examination for men and a vaginal examination for women. Blood and urine tests will be arranged and if infection is suspected, antibiotics may be prescribed. If the tests do not indicate infection, then the patient is referred to a specialist.



Further Reading

Last Updated: Feb 26, 2019

Sally Robertson

Written by

Sally Robertson

Sally first developed an interest in medical communications when she took on the role of Journal Development Editor for BioMed Central (BMC), after having graduated with a degree in biomedical science from Greenwich University.


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