Seeing blood in your urine can be alarming. The medical term for this is hematuria. Sometimes the blood is visible, and sometimes it is found only on a urine test. Hematuria is not a diagnosis by itself. It is a sign that should be evaluated to find the cause.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIH), blood in the urine can come from the kidneys or from another part of the urinary tract, and causes may range from infections and kidney stones to kidney disease or, in some cases, cancer.
At Florida Kidney Physicians, our goal is to help you understand what hematuria means, what may cause it, and when it is important to seek medical care.
What Is Hematuria?
Hematuria means that red blood cells are present in the urine. If there is enough blood, the urine may look pink, red, brown, or tea-colored. In other cases, the urine looks normal and the blood is found only during a urinalysis or microscopic exam. Gross hematuria is visible to the eye. Microscopic hematuria is detected only through testing.
A small amount of blood can noticeably change the color of urine, so the color alone does not always tell you how much bleeding is present. What matters most is that blood in the urine should not be ignored.
It is also important to know that not every red or dark urine sample contains blood. Certain foods, medicines, or colorings can change urine color. For example, beets may turn urine pink or red, and some medicines, including rifampin or nitrofurantoin, can darken the urine. Even so, if you are not sure why your urine changed color, it is best to contact your healthcare professional rather than assume it is harmless.
Gross Hematuria vs. Microscopic Hematuria
Gross hematuria means the blood is visible. Your urine may appear light pink, bright red, brown, or tea- or cola-colored. Gross hematuria should always be taken seriously, even if it happens only once.
Microscopic hematuria means red blood cells are present in the urine but cannot be seen without testing. It may be found during a routine urinalysis or while checking for another problem. A clinician may repeat the urine test to confirm that red blood cells are truly present before deciding what evaluation is needed next.
When Hematuria May Suggest a Kidney Filtering Problem
Some cases of hematuria begin in the kidneys themselves, especially in the glomeruli, which are the tiny filtering units inside the kidneys. The National Kidney Foundation explains that the glomeruli work like a selective filtration barrier. They allow waste and extra water to pass into the urine while normally keeping blood cells and most protein in the bloodstream. When that filtering barrier becomes inflamed or injured, it can lose some of its ability to hold red blood cells back. As a result, red blood cells can leak into the urine.
This is one reason doctors think differently about glomerular hematuria and non-glomerular hematuria.
Hematuria that may be coming from the kidney filter is more likely to appear with clues such as:
- protein in the urine
- swelling
- high blood pressure
- darker urine that looks tea-colored or cola-colored
Hematuria that may be coming from elsewhere in the urinary tract is more often associated with clues such as:
- burning with urination
- urinary urgency or frequency
- flank pain or colicky pain
- bright red urine or visible clots
These are not absolute rules, but they can help guide evaluation. When blood in the urine appears together with proteinuria, swelling, or high blood pressure, the kidneys deserve especially careful attention as a possible source.
Sometimes the urine test itself can offer clues about where the blood may be coming from. A urinalysis may suggest whether the problem is more likely related to the kidney filter or to another part of the urinary tract, which helps determine whether nephrology, urology, or both may need to be involved.
Common Causes of Hematuria
Infections and Stones
Urinary tract infections can irritate the lining of the bladder or urethra and lead to blood in the urine. Other symptoms may include burning with urination, urgency, frequent urination, cloudy urine, or lower abdominal discomfort.
Kidney stones can also cause hematuria. As a stone moves through the urinary tract, it can scrape or irritate the lining and cause bleeding. Stones may also cause severe side pain, back pain, nausea, or painful urination.
Kidney or Glomerular Causes
Kidney disorders such as glomerular diseases can cause hematuria when the kidney’s filtering units are damaged. In these situations, blood in the urine may appear along with proteinuria, swelling, or elevated blood pressure.
Trauma and Exercise
A fall, accident, or other injury involving the kidneys or bladder can lead to hematuria and should be evaluated promptly.
Strenuous exercise, including long-distance running, can sometimes be associated with temporary hematuria. However, this should be treated as a diagnosis of exclusion. Blood in the urine should never be assumed to be “just from exercise” until a clinician has ruled out other possible causes.
Medicines
Some medicines can be associated with blood in the urine or may increase the chance of bleeding. These can include blood thinners, aspirin, some antibiotics, and other pain relievers. Long-term or heavy use of NSAIDs such as ibuprofen or naproxen can also contribute to kidney injury in some people. But the presence of one of these medicines does not automatically explain hematuria by itself. Evaluation is still important. Patients should not stop prescribed anticoagulants, NSAIDs, or other medications on their own without speaking with their clinician.
Causes That Require Careful Exclusion
Although many causes of hematuria are not cancerous, blood in the urine in adults over 35 to 40, people with a smoking history, or people with persistent or recurrent hematuria deserves especially careful evaluation. The AUA/SUFU guideline uses a risk-based approach for microhematuria, and the National Kidney Foundation also notes that blood in the urine in adults can sometimes be linked to urinary tract cancers.
What Hematuria Does Not Tell You by Itself
Blood in the urine is important, but by itself it does not tell you everything. Hematuria does not automatically mean:
- that you have a urinary tract infection
- that you have cancer
- that the kidneys are definitely the source
- that the cause is harmless because it happened only once
The goal of evaluation is not just to confirm that blood is present. It is to determine whether the source is glomerular, urologic, infectious, stone-related, medication-related, traumatic, or, less commonly, malignant.
When to Seek Medical Attention
You should contact your doctor, nephrologist, or urologist if you notice blood in your urine, even if it happens only once. A single episode still deserves attention, and persistent or recurrent hematuria usually increases the need for a more complete workup.
Seek prompt or urgent care if blood in the urine happens along with:
- severe flank, back, or abdominal pain
- fever or chills
- difficulty urinating
- clots that seem to block urine flow
- marked weakness, dizziness, or worsening symptoms
Blood clots can be painful to pass and can sometimes block urine flow, which is one reason hematuria can become an urgent issue.
Do not assume the cause is exercise, menstruation, food, a past infection, or medication without medical evaluation.
How Doctors Tell Whether Blood in the Urine Comes From the Kidney or the Urinary Tract
Kidney disease doctors usually evaluate hematuria in a step-by-step way.
First, they confirm that red blood cells are really present in the urine.
Second, they look for clues about whether the source is more likely the kidney or another part of the urinary tract.
Third, they decide whether blood tests, imaging, cystoscopy, repeat urinalysis, or referral to nephrology or urology is needed.
The evaluation may differ depending on your age, symptoms, smoking history, kidney function, and whether the hematuria is visible or found only on testing.
Key Terms
Glomerulus: a tiny filter in the kidney that helps remove waste and extra water while normally keeping blood cells and most protein in the bloodstream.
Proteinuria: protein in the urine. It can happen when the kidney’s filtering units are damaged.
Creatinine: a waste product measured in blood tests to help assess kidney function.
Urinalysis: a urine test that checks physical, chemical, and microscopic features of urine.
Nephrologist: a doctor who specializes in kidney diseases.
Urologist: a doctor who specializes in the urinary tract and related structures.
FAQs
Can blood in the urine come from the kidneys?
Yes. Blood in the urine can come from the kidneys, especially when the glomeruli—the kidney’s filtering units—are inflamed or damaged. It can also come from another part of the urinary tract, which is why evaluation is important.
Is blood in the urine always a sign of cancer?
No. Many causes of hematuria are not cancerous, including infections, kidney stones, and some kidney disorders. Still, blood in the urine should be evaluated, especially in older adults, smokers, or people with persistent hematuria.
Can exercise cause hematuria?
Yes, strenuous exercise can sometimes cause temporary hematuria. But it should never be assumed to be the cause until a clinician has ruled out other possible explanations.
What tests are usually done for hematuria?
Evaluation often starts with a urinalysis and medical history. Depending on the situation, doctors may repeat the urine test, order blood tests or imaging, and decide whether nephrology or urology evaluation is needed.
A Final Word
Hematuria can be unsettling, but it should not be ignored or self-diagnosed. Blood in the urine may come from a urinary infection, a kidney stone, a kidney filtering problem, trauma, medication-related bleeding, or a more serious condition. The purpose of medical evaluation is not only to confirm that blood is present, but to identify whether the source is glomerular, urologic, infectious, stone-related, or, in some cases, malignant. That is the key step toward the right treatment and follow-up.