Hematuria is the medical term for blood in your urine. It can be visible to the naked eye, turning urine pink, red, or cola-colored, or it can be invisible, detectable only under a microscope during a routine test. It affects an estimated 6.5% of the U.S. population, and while it often stems from something harmless, it sometimes signals a condition that needs attention.
Two Types: Visible and Microscopic
Hematuria falls into two categories based on whether you can see it. Gross hematuria means the blood is visible. Even a tiny amount of blood can change urine color dramatically, so a bright red toilet bowl doesn’t necessarily mean heavy bleeding. Microscopic hematuria, on the other hand, shows up only when a urine sample is examined under a microscope during a checkup or screening for something else entirely.
Microscopic hematuria is surprisingly common. Prevalence estimates range from about 2% to 31% depending on the population studied, with older men being especially prone. Some estimates put the rate as high as 21% in older men. Many of these cases are completely benign, but the finding still warrants a closer look.
Common Causes
The list of things that can put blood in your urine is long, but most cases trace back to a handful of familiar culprits:
- Urinary tract infections (UTIs): Infection or inflammation in the bladder, kidney, or urethra is one of the most frequent causes, especially in women.
- Kidney or bladder stones: Hard mineral deposits can scrape the lining of your urinary tract as they move through it.
- Enlarged prostate: In men, a growing prostate gland can compress nearby blood vessels and cause bleeding.
- Vigorous exercise: Long-distance running and other strenuous activities can trigger hematuria, sometimes called “runner’s hematuria.” It typically resolves within a few days of rest without any treatment.
- Sexual activity: Physical irritation during sex can occasionally produce trace amounts of blood.
- Endometriosis: In some women, tissue that normally lines the uterus grows into or near the urinary tract.
- Medications: Blood thinners, aspirin, and certain antibiotics can increase the risk.
- Recent infections: A bacterial or viral illness, such as strep throat or hepatitis, can temporarily affect the kidneys and cause blood to leak into the urine.
More Serious Possibilities
In a smaller number of cases, hematuria points to something that requires prompt treatment. Bladder, kidney, or prostate cancer can all cause blood in the urine. A population-based study found that about 11% of patients with visible hematuria were ultimately diagnosed with a urinary tract malignancy. For microscopic hematuria discovered without symptoms, that number drops to roughly 2%.
Other serious causes include blood-clotting disorders like hemophilia, sickle cell disease, and a type of kidney disease called glomerulonephritis, where the tiny filters inside your kidneys become inflamed and let red blood cells pass through. These conditions usually come with additional symptoms, such as swelling, fatigue, or frequent bruising.
Red Urine That Isn’t Blood
Not every red toilet bowl means hematuria. Beets are a well-known culprit. Eating beets or beet-colored foods can turn urine pink or red, a harmless phenomenon called beeturia. Foods high in oxalic acid, like spinach and rhubarb, can increase the effect. Certain medications also change urine color without any blood being present. If you’ve recently eaten beets or started a new medication and notice discolored urine, a simple urine test can confirm whether red blood cells are actually there.
How Hematuria Is Diagnosed
The starting point is a urinalysis, a basic urine test that checks for red blood cells, infection, and protein. If blood is confirmed, the next steps depend on your age, sex, smoking history, and whether the hematuria is visible or microscopic.
For most adults who need imaging, a CT urogram is the preferred test. It uses contrast dye and a CT scanner to produce detailed images of the kidneys, ureters, and bladder in a single exam. A large meta-analysis found it detects urothelial cancers with 96% sensitivity and 99% specificity, making it far more accurate than older imaging methods. Ultrasound, while radiation-free, misses more abnormalities and is not typically the first choice for evaluating hematuria. One study found ultrasound had just 35% sensitivity for detecting the cause of gross hematuria compared to cystoscopy.
Cystoscopy, where a thin camera is guided through the urethra into the bladder, is often recommended alongside imaging. It gives doctors a direct view of the bladder lining and can spot tumors or other abnormalities that even a CT might miss. The procedure is usually done in an office setting with local numbing gel and takes only a few minutes, though it can be uncomfortable.
Risk Factors That Raise Concern
Doctors weigh several factors when deciding how aggressively to investigate hematuria. Visible blood in the urine is treated more seriously than a microscopic finding because the cancer detection rate is roughly five times higher. A history of smoking is one of the strongest risk factors for bladder cancer. Age matters too: urinary tract cancers are rare in younger adults but become increasingly common after 40. Other red flags include a history of pelvic radiation, exposure to certain industrial chemicals, and persistent or recurrent hematuria over multiple urine tests.
If you fall into a lower-risk category, your doctor may recommend repeating a urinalysis in a few months rather than jumping straight to imaging. Many cases of microscopic hematuria, particularly in younger women with a recent UTI, resolve on their own once the underlying cause is treated. If repeat testing still shows blood, further workup becomes more important.
What to Expect if You’re Told You Have It
Finding blood in your urine, whether you see it yourself or learn about it from a lab report, is understandably alarming. But most causes are treatable and not life-threatening. UTIs clear with antibiotics. Kidney stones pass or can be broken up. Exercise-induced hematuria resolves with rest. Even when the workup leads to a cancer diagnosis, catching it through hematuria often means it’s found early, when treatment is most effective.
The most important thing is not to ignore it. Visible blood in your urine always warrants evaluation. Microscopic hematuria found on a routine test deserves follow-up, even if you feel perfectly fine. In many cases the answer will be reassuring, but the evaluation itself is what gives you that reassurance.