Blood in your urine, even a small amount, is your body signaling that something needs attention. The most common cause in women is a urinary tract infection, but the list of possibilities ranges from completely harmless to serious. About 20% of women will show trace amounts of blood in a urine test at some point, so while it’s common, it always deserves investigation.
Urinary Tract Infections: The Most Likely Cause
UTIs are the single most frequent reason women see blood when they pee. Bacteria enter the urethra (the short tube urine exits through) and multiply in the bladder, irritating the lining enough to cause bleeding. Because the female urethra is much shorter than the male one, bacteria have a shorter path to travel, which is why UTIs are far more common in women.
If a UTI is behind the bleeding, you’ll usually notice other symptoms alongside it: a persistent, urgent need to pee, a burning sensation during urination, and urine that smells unusually strong. The blood itself can make your urine look pink, red, or brownish. A simple urine test at your doctor’s office confirms the diagnosis, and a course of antibiotics typically clears it within a few days.
Kidney Stones
Kidney stones form when minerals in your urine crystallize into hard deposits. As a stone moves through the urinary tract, it scrapes the delicate tissue lining the ureters (the tubes connecting your kidneys to your bladder) or the urethra, causing bleeding. The hallmark of a kidney stone is intense, wave-like pain in your side or lower back that can radiate toward your groin. Nausea and vomiting often come with it. Some smaller stones pass on their own with fluids and pain management, while larger ones may need medical intervention to break them up.
Bladder or Kidney Cancer
This is the possibility most people worry about, and while it’s far less common than a UTI or kidney stone, it’s the reason blood in your urine should never be ignored. Blood in the urine is the most common first symptom of bladder cancer. As one urologic surgeon at MD Anderson Cancer Center put it, it’s the leading symptom “far and away.” The bleeding can be dramatic or barely noticeable. One patient described it as “the slightest shade of pink you can imagine,” and it only happened once.
Risk factors include smoking, age over 55, and a history of chronic bladder infections. Bladder cancer is more common in men, but women are often diagnosed at a later stage because the bleeding gets attributed to other causes first. Painless blood in the urine, especially if you’re over 40 and don’t have other UTI symptoms, warrants prompt evaluation.
Endometriosis Involving the Bladder
Endometriosis happens when tissue similar to the uterine lining grows outside the uterus. In rare cases (about 1 to 2% of women with endometriosis), that tissue attaches to parts of the urinary tract. The bladder is the most common site, accounting for roughly 84% of urinary tract endometriosis cases.
The telltale clue is timing. Bladder endometriosis causes cyclical symptoms that track with your menstrual cycle: urgency, pain above the pubic bone, and blood in the urine that comes and goes with your period. Cyclical bleeding during urination is considered a hallmark sign, though only about 20% of women with bladder endometriosis actually experience it. If you notice that bloody urine consistently appears around your period, bring that pattern to your doctor’s attention.
Medications and Intense Exercise
Certain medications can cause bleeding in the urinary tract as a side effect. Blood thinners are the most common culprits, but penicillins and sulfa-containing drugs can also be responsible. If you recently started a new medication and noticed pink or red urine, the timing may not be a coincidence.
Strenuous exercise, particularly long-distance running, can produce blood in the urine temporarily. This is generally harmless and resolves on its own within 24 to 72 hours. If it doesn’t clear up after rest, something else is going on.
When It’s Not Actually Blood
Before you panic, consider what you’ve eaten or taken recently. Beets, blackberries, and rhubarb can all turn urine red or pink. So can certain medications: rifampin (used for tuberculosis), phenazopyridine (a common over-the-counter bladder pain reliever), and senna-based laxatives. If your urine looks alarming but you have zero pain or other symptoms and recently ate a beet salad, that may be your answer. A urinalysis will confirm whether actual blood is present.
How Doctors Find the Cause
The first step is a urinalysis, a simple urine test that confirms whether blood is genuinely present and checks for signs of infection. From there, your doctor may order imaging to look at your kidneys, bladder, and ureters. A CT scan provides the most detailed view and is commonly used to spot stones, tumors, or structural problems. An ultrasound is sometimes used as an alternative, especially when avoiding radiation is preferred.
If imaging doesn’t reveal a cause, a cystoscopy may be recommended. This involves a thin, flexible camera inserted through the urethra to visually inspect the bladder lining. It sounds uncomfortable, but it’s a quick outpatient procedure and is the most direct way to check for bladder abnormalities. If a prior workup came back normal but you later develop visible blood, a significant increase in the amount of microscopic blood, or new urinary symptoms, current urology guidelines recommend starting the evaluation process again rather than assuming the original results still apply.
Signs You Need Urgent Care
Most causes of blood in urine aren’t emergencies, but certain combinations of symptoms are. You should seek immediate medical attention if you see blood clots in your urine, if you’re unable to urinate at all, or if the bleeding comes with fever, chills, nausea, vomiting, or significant pain in your side, back, or abdomen. These can indicate a serious infection spreading to the kidneys, a large stone causing a blockage, or another condition that needs treatment right away.