A urinary tract infection (UTI) is a common bacterial infection that typically affects the bladder and urethra. The presence of blood in the urine, known medically as hematuria, is a symptom that can accompany this infection and is often the cause of significant alarm. While the sight of pink, red, or cola-colored urine is frightening, it is a common manifestation of the inflammation caused by the infection. Understanding the underlying mechanism and expected timeline for resolution helps manage concern while seeking appropriate medical treatment.
The Cause of Bleeding During a UTI
The appearance of blood in the urine is a direct consequence of the body’s response to invading bacteria within the urinary tract. Bacteria, most commonly Escherichia coli, colonize the lining of the bladder and urethra, triggering an intense inflammatory response. This inflammation irritates the delicate tissue lining the urinary tract, known as the urothelium.
The irritation and swelling cause the small, superficial blood vessels near the surface of the lining to become fragile and temporarily damaged. This fragility allows red blood cells to leak out and mix with the urine. When the amount of blood is large enough to be seen with the naked eye, it is termed gross hematuria, resulting in visible discoloration.
In many cases, the amount of blood is minimal and only detectable when a urine sample is analyzed under a microscope; this is microscopic hematuria. Both forms of bleeding point to the same underlying cause: localized irritation and tissue damage from the bacterial infection.
Typical Timeline for Hematuria Resolution
The duration of bleeding is directly related to the persistence of the bacterial infection and the resulting inflammation. Once antibiotic treatment begins, the cessation of visible bleeding is usually one of the first signs that the treatment is effective. For gross hematuria, the visible discoloration of the urine typically begins to subside quickly, often within 24 to 72 hours of starting the appropriate medication.
The rapid disappearance of visible blood is a sign that the bacterial load is decreasing and the acute inflammatory response is calming down. It is important to continue the full course of antibiotics as prescribed, even if the urine color returns to normal and other symptoms improve. If the visible bleeding does not show improvement or continues beyond three days of antibiotic treatment, a follow-up consultation with a healthcare provider is warranted.
In contrast, the resolution of microscopic hematuria can take a significantly longer time. Studies have shown that it can take a median of 66 days for all traces of microscopic blood to clear from the urine following a successfully treated UTI. The presence of microscopic blood in a follow-up urine test does not necessarily indicate a treatment failure unless other symptoms of the infection are still present. This delayed resolution reflects the time required for the urothelium to fully heal and repair itself.
Indicators That Require Immediate Medical Attention
While gross hematuria is a common symptom of a lower UTI, its presence combined with certain other symptoms can indicate a more serious condition, such as a kidney infection. High fever (above 101°F), accompanied by shaking chills or uncontrollable shivering, requires immediate attention. These systemic symptoms suggest the infection has traveled from the bladder up to the kidneys, a condition called pyelonephritis.
Severe pain localized in the flank area (the side and back below the ribs) also strongly suggests the infection has reached the kidneys. Nausea and persistent vomiting necessitate prompt medical evaluation, as they can lead to dehydration and interfere with taking oral antibiotics. These symptoms indicate a risk of the infection spreading to the bloodstream, which is a severe complication.
Any instance of bleeding that involves passing large blood clots or an inability to urinate should be treated as an urgent medical situation. Bleeding that occurs without the typical painful urination, urgency, or frequency associated with a UTI should also be reported immediately. Hematuria can also be a symptom of other conditions, such as kidney stones, and requires a full evaluation to rule out other potential causes.