Occult Blood in Urine: Meaning, Causes and Care
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Introduction
Occult blood in urine means a urine test found blood that was not visible 1,5. Clinicians call this finding microscopic hematuria, or microhematuria 5,6. The urine often looks normal, and many people have no symptoms 5,6.
A positive result does not reveal why bleeding occurred. Infection, stones, exercise, kidney disease, and cancer can cause blood in urine 1,5. Follow-up testing confirms the result and helps find the source 1,5.
This article explains occult blood in urine symptoms, causes, what it means, and when to seek care. It also explains testing, treatment, and follow-up.
Overview: What Occult Blood in Urine Means
Occult blood and microscopic hematuria
“Occult” means hidden, so occult blood cannot be seen without testing 8. Hematuria is the medical term for blood in urine 1,5.
Microscopic hematuria means that testing found blood in urine that looks normal 5,6. A laboratory can find the blood through urinalysis or examination under a microscope 1,5. Urinalysis is a test that checks urine for cells, chemicals, and other substances 1.
Red blood cells may come from the kidneys or any part of the urinary tract 9. The urinary tract includes the kidneys, ureters, bladder, and urethra 5,9. The ureters carry urine from the kidneys to the bladder 5.
Clinicians commonly define microscopic hematuria as three or more red blood cells per high-power field 3,6. A high-power field is the small area seen through a microscope.
Microscopic versus visible blood in urine
Microscopic hematuria does not change urine color and typically causes no symptoms 5. Gross hematuria means that blood is visible without a microscope 1,5.
Visible blood may make urine look pink, red, brown, or tea-colored 3,5. Only a small amount of blood is needed to change the color 5,10. Urine that looks bloody should receive medical evaluation 4,10.
Red urine does not always contain blood. Beets, rhubarb, and some medicines can change urine color 1,10. Testing can help tell whether a color change comes from blood.
What a positive urine dipstick can show
A dipstick is a treated strip used to test a urine sample. A positive dipstick alone does not confirm microscopic hematuria 3.
A dipstick may react to red blood cells, free hemoglobin, or myoglobin 3. Hemoglobin is the substance in red blood cells that carries oxygen. Myoglobin is a protein found in muscle.
Microscopy should confirm whether intact red blood cells are present 3. A positive dipstick without red cells may reflect hemoglobin or myoglobin 3. For this reason, clinicians should not rely on dipstick testing alone 3.
Symptoms That May Occur With Occult Blood
Why microscopic hematuria often has no symptoms
Microscopic hematuria often causes no symptoms or visible change in urine 5,6. Clinicians may discover it during routine testing at a checkup 6.
Symptoms, when present, may offer clues about the cause. Their timing and location are useful details to share during a medical visit.
Urinary symptoms to notice
A urinary tract infection may cause burning, urgency, or frequent urination 2,10. Urgency means a strong need to urinate. An infection may also cause strong or foul-smelling urine 6,10.
Prostate problems can change the flow of urine. An enlarged prostate may cause trouble starting urination or a lasting urge to urinate 10. It may also cause dribbling or nighttime urination 2.
Symptoms worth reporting to a healthcare professional include the following:
Pain or burning during urination may occur with a urinary tract infection 2,10.
Frequent or urgent urination may occur with infection or prostate enlargement 2,10.
Strong or foul-smelling urine may occur with a urinary tract infection 6,10.
Dribbling may occur with a prostate problem 2.
Trouble starting urine flow may occur with prostate enlargement 2,10.
These symptoms do not identify the cause by themselves. A clinician may use urine testing and other exams to investigate them 5,6.
Pain, fever, and other symptoms
Urinary stones can cause severe pain when they move or block urine flow 10. Pain may affect the abdomen, back, side, or groin 2,10. Stones can cause either visible or microscopic blood in urine 10.
A kidney infection may cause fever and pain in the back, side, or groin 10. It can also cause urinary symptoms like those linked with bladder infections 10.
Blood clots may hurt or block urine flow 5. Passing a clot can also cause pain during urination 5. Visible clots are different from hidden blood found only by testing.
Contact a healthcare professional right away in these situations:
If fever or shaking chills occur with hematuria, contact a healthcare professional right away 2.
If nausea or vomiting occurs with hematuria, contact a healthcare professional right away 2.
If abdominal, side, or back pain occurs, contact a healthcare professional right away 2.
If urine cannot pass, contact a healthcare professional right away 2.
If blood clots pass in urine, contact a healthcare professional right away 2.
Unexplained weight loss with hematuria should also be reported to a clinician 2.
Signs linked with kidney disease
Kidney disease can cause blood found only through laboratory testing 10. Glomerulonephritis is inflammation of the kidney’s small filters 10.
Microscopic blood with urine protein can point toward disease in these filters 3. Clinicians may use blood and urine tests to check kidney function 5,6.
Causes of Occult Blood in Urine
Occult blood in urine has many possible causes. Some causes are brief, while others need more testing.
Urinary tract infections
Infections of the bladder, kidney, prostate, or urethra can cause hematuria 1,2. The urethra is the tube that carries urine out of the body 5. Bacteria cause many urinary tract infections 10.
Bladder infections may cause burning, urgency, and frequent urination 10. Kidney infections are more likely to cause fever and back or side pain 10. A urine culture can help identify a urinary tract infection 2,6.
Stones and inflammation
Kidney or bladder stones can cause blood in urine 1,5. Stones may cause pain when they pass or block urine flow 10. Some stones cause bleeding found only during laboratory testing 10.
Inflammation may affect the bladder, urethra, prostate, or kidney 1,2. Glomerulonephritis affects the kidney’s filtering units 10. It may occur alone or as part of another illness 10.
Benign prostate enlargement
Benign prostatic hyperplasia means noncancerous enlargement of the prostate. The prostate sits below the bladder and surrounds part of the urethra 10.
An enlarged prostate may press on the urethra and partly block urine flow 10. It can cause hematuria, urgency, or trouble urinating 1,10. Prostate infection may cause similar urinary symptoms 10.
Vigorous exercise and sexual activity
Vigorous exercise can cause blood in urine 5,10. Examples in the sources include contact sports and long-distance running 10.
Visible blood after exercise should still be reported to a healthcare professional 10. Exercise should not be assumed to be the cause without medical review 10.
Sexual activity is another possible cause of temporary hematuria 1,5. A clinician may ask about recent activity when reviewing the test result.
Injury and recent procedures
An injury to the bladder or kidney can cause hematuria 2,10. Such injuries may follow an accident or contact sport 1,10.
Recent urinary procedures can also cause bleeding 1,2. Examples include catheter use, surgery, circumcision, or kidney biopsy 2. Sharing this history can help a clinician assess the result.
Medicines and blood thinners
Certain medicines are linked with blood in urine 1,5. These include aspirin and medicines that reduce blood clotting 2,5.
Anticoagulants are medicines that help prevent blood clots. They may worsen urinary bleeding but do not remove the need for evaluation 3. People taking anticoagulants should receive the same risk-based assessment as other patients 3.
Do not stop aspirin or another medicine without instructions from its prescriber 1. Tell the clinician about all medicines, vitamins, and supplements 7.
Menstrual blood and sample contamination
Blood in a urine container may come from outside the urinary tract 1,2. This can make a test result misleading.
Common sources of outside blood include the following:
Menstrual blood can enter the sample and produce a positive result 1,5.
Vaginal or rectal bleeding can contaminate a urine sample 2,3.
Bleeding hemorrhoids can affect a urine test result 1.
Blood linked with ejaculation may appear to come from urine 2.
A clean-catch sample helps reduce contamination from skin and outside material 1. Testing may be repeated after menstrual bleeding ends 5.
Kidney disease and blood disorders
Glomerular kidney disease can cause microscopic hematuria 5,10. “Glomerular” refers to the kidney’s small blood-filtering units. Polycystic kidney disease can also cause blood in urine 1,2.
Blood-clotting disorders are other possible causes 2,5. These include hemophilia and low platelet counts 2. Platelets are blood cells that help form clots.
Sickle cell disease can cause visible or microscopic hematuria 2,5. A blood clot within the kidney can also cause urinary bleeding 2.
Bladder, kidney, and prostate cancer
Cancer of the bladder, kidney, or prostate can cause hematuria 1,5. Hematuria is often the earliest sign of a kidney tumor 3. It is also a common presenting sign of bladder cancer 3.
Cancer risk can rise with older age and a history of smoking 3,4. Certain chemical exposures also increase concern 3. Examples include benzene and aromatic amines 3.
Visible blood and greater amounts of blood can raise the level of concern 3. Persistent hematuria may also lead to further testing and follow-up 4,7.
Many other conditions can cause blood in urine 1. Still, unexplained blood should not be ignored.
How Clinicians Confirm and Evaluate the Finding
Repeat urinalysis and clean-catch collection
A clinician may repeat urinalysis to confirm hematuria 5,7. Urinalysis can check urine for blood, protein, cells, chemicals, and crystals 1.
Clean-catch collection helps keep germs and outside blood from entering the sample 1. The genital area is cleaned before collection 1. Some urine first passes into the toilet 1.
The next part of the urine stream enters the container 1. The container should not touch the body during collection 1.
Tell the clinician about menstruation, hemorrhoids, or other bleeding before testing 1. A repeat sample may be collected after menstruation stops 5.
Microscopy then checks for red blood cells 3. Three or more cells per high-power field commonly confirms microscopic hematuria 3,6.
Medical history and physical examination
The clinician may ask about pain, urinary symptoms, infections, injuries, and procedures 2. Questions may also cover medicines, exercise, and past urinary problems 2.
Smoking history and chemical exposure can affect the evaluation 3. The clinician may also ask about visible blood and weight changes 2,6.
A physical examination may include a blood pressure check 3. It may also include a pelvic or rectal examination 5.
Urine and blood tests
A urine culture can help diagnose a urinary tract infection 6. Urine protein can point toward disease in the kidney filters 3.
Microscopy may find crystals, casts, or red cells with unusual shapes 3. Casts are small, tube-shaped particles formed inside the kidneys.
Blood tests may check kidney function or signs of other diseases 5,6. A creatinine test helps assess kidney function 2,3. A blood count can show platelet or blood cell problems 2,6.
Imaging, cystoscopy, and referral
Further testing depends on symptoms, risk factors, and confirmed findings. A clinician may recommend tests from this list:
Ultrasound uses sound waves to make images of organs, including the kidneys 5.
CT imaging creates detailed pictures of the urinary tract 5,6.
MRI creates images of organs without using X-rays 5.
Cystoscopy uses a thin camera to examine the urethra and bladder 5,7.
Kidney biopsy checks a small tissue sample for kidney disease or damage 5.
Cystoscopy can detect some small or flat bladder tumors that imaging may miss 4. A urologist specializes in conditions of the urinary tract 7. A nephrologist specializes in kidney conditions 4.
Age, smoking, chemical exposure, and visible bleeding may affect further testing 3. Some people need specialist care or continued monitoring 4,7. Sometimes a complete evaluation does not find a cause 4,7.
Treatment for Occult Blood in Urine
Treatment depends on the cause of the bleeding 2,5. The positive test alone does not select a treatment.
Antibiotics may treat a urinary tract infection 6,7. They are used when the infection is bacterial 7.
Stone care may include medicine, sound waves, or surgery 6,7. The chosen treatment depends on the problem found during evaluation.
Medicine may relax the prostate or slow its growth 6. Surgery may remove prostate tissue in some cases 6.
Care for kidney disease depends on the condition found. Blood disorders and cancers also need care based on the specific diagnosis.
Some people need no treatment when testing finds no serious cause 5,7. A clinician may instead recommend monitoring and repeat urinalysis 6. Follow-up testing can show whether blood remains in the urine 4,7.
When to See a Doctor
When to seek care right away
Certain symptoms need medical contact right away. Use the following guidance if these problems occur:
If urine cannot pass, contact a healthcare professional right away 2.
If blood clots pass in urine, contact a healthcare professional right away 2.
If fever or shaking chills occur, contact a healthcare professional right away 2.
If vomiting occurs with hematuria, contact a healthcare professional right away 2.
If abdominal, side, or back pain occurs, contact a healthcare professional right away 2.
These symptoms can occur with problems such as infection, stones, or blocked urine flow 5,10.
When to arrange a medical appointment
Contact a healthcare professional whenever urine looks bloody 10. Visible blood should receive medical evaluation even when it does not hurt 4,10.
A confirmed occult blood result should also be discussed with a clinician. Persistent hematuria or urinary symptoms may require more tests 3,4.
Report unexplained weight loss with hematuria to a healthcare professional 2. Also report burning, urgency, frequent urination, or trouble starting urine flow 2.
Do not assume a blood thinner is the only cause of bleeding 3. People taking anticoagulants still need an appropriate hematuria evaluation 3.
Conclusion
Understanding occult blood in urine symptoms, causes, what it means, and when to seek care supports informed action. Microscopic hematuria often causes no symptoms or change in urine color 5,6.
A positive dipstick needs microscopic confirmation 3. Dipstick testing alone does not prove that intact red blood cells are present 3.
Confirmed microscopic hematuria commonly means three or more red cells per high-power field 3,6. A clean-catch sample can reduce misleading results from outside blood 1.
Possible causes include infection, stones, exercise, trauma, prostate enlargement, and urinary procedures 1,5. Kidney disease, blood disorders, sickle cell disease, and urinary cancers are also possible causes 2,5.
Treatment targets the cause 2,5. Some people need monitoring rather than immediate treatment 5,6. Medical review can confirm the finding and guide the next steps.
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