A urinary tract infection, or UTI, is a bacterial infection anywhere in your urinary system: the kidneys, ureters, bladder, or urethra. Most UTIs stay in the lower tract, affecting the bladder and urethra, and clear up quickly with antibiotics. If the infection travels to the kidneys, though, it becomes a more serious condition that may need stronger treatment.
UTIs are one of the most common infections worldwide, and they’re far more frequent in women than men due to differences in anatomy. Understanding the symptoms, what causes them, and how to reduce your risk can help you catch one early and recover faster.
What Causes a UTI
The vast majority of UTIs are caused by Escherichia coli, a type of bacteria that normally lives in the digestive tract. When these bacteria make their way into the urethra (the tube urine exits through), they can travel upward into the bladder and multiply. Less commonly, other bacteria or even yeast can cause urinary infections, particularly in people who are hospitalized or have catheters.
Women get UTIs far more often than men, primarily because the female urethra is shorter, which gives bacteria a shorter path to the bladder. The opening of the urethra is also closer to the rectum, making it easier for gut bacteria to migrate to the urinary tract. Sexual activity can push bacteria toward the urethra as well, and certain contraceptive methods like spermicides increase risk by disrupting the balance of protective bacteria in the vaginal area.
Common Symptoms
A bladder infection, the most common type of UTI, typically produces a recognizable set of symptoms:
- A strong, persistent urge to urinate, even when little comes out
- A burning or stinging sensation during urination
- Passing small amounts of urine frequently throughout the day
- Cloudy, dark, or strong-smelling urine
- Blood in the urine, which may appear pink or reddish
- Pressure or discomfort in the lower abdomen or pelvic area
- A low-grade fever
Not everyone experiences all of these. Some people, especially older adults, may have fewer obvious symptoms. There’s a common assumption that sudden confusion in an elderly person signals a UTI, but Cleveland Clinic experts note that delirium in older adults is more often caused by dehydration and other factors. A urine test is needed to confirm the infection rather than relying on behavioral changes alone.
When a UTI Reaches the Kidneys
If a bladder infection isn’t treated or doesn’t respond to treatment, bacteria can travel up through the ureters to the kidneys. A kidney infection is more serious than a simple bladder infection and produces more intense symptoms: fever and chills, pain in your back or side, nausea, and vomiting. You’ll often still have the burning and frequent urination of a lower UTI, but the fever and flank pain are the key signs that the infection has moved higher.
In rare cases, a kidney infection can lead to sepsis, a dangerous whole-body response. Warning signs of sepsis include confusion, rapid breathing and heart rate, and severe discomfort. Children under two with a kidney infection may only show a high fever along with feeding difficulties, making it harder to recognize.
How UTIs Are Diagnosed
Diagnosis usually starts with a urine sample. A standard urinalysis can detect white blood cells, bacteria, and blood. If more detail is needed, a urine culture grows the bacteria in a lab to identify the exact species and determine which antibiotics will work against it. A culture is considered positive when it shows at least 100,000 colony-forming units per milliliter of a single bacterial species. If more than two types of bacteria show up, it often means the sample was contaminated rather than reflecting a true infection.
For a straightforward UTI with typical symptoms, many clinicians will start treatment based on the initial urinalysis without waiting for culture results, then adjust if needed.
Treatment for Uncomplicated UTIs
Most bladder infections in otherwise healthy people are treated with a short course of oral antibiotics. According to a 2024 review in American Family Physician, first-line options for women include nitrofurantoin for five days, a single dose of fosfomycin, or trimethoprim/sulfamethoxazole for three days (as long as local bacterial resistance to that drug is below 20%). For men without fever, a seven-day course is typically as effective as a longer one.
Fluoroquinolones work against UTIs but are reserved as a backup option because of their risk of serious side effects and the growing problem of bacterial resistance. Symptoms often start improving within a day or two of starting antibiotics, though it’s important to finish the full course.
Complicated UTIs, those involving kidney infections, structural abnormalities, or patients who are very ill, may initially require intravenous antibiotics in a hospital setting. Once symptoms improve and the patient can tolerate oral medication, guidelines support switching to oral antibiotics for the remainder of treatment.
Who Gets UTIs More Often
Several factors raise your likelihood of getting a UTI or getting them repeatedly. Being sexually active is one of the biggest risk factors for women. Using spermicides or barrier contraceptives increases risk because these products can reduce levels of protective Lactobacillus bacteria in the vaginal area.
Postmenopausal women face higher risk as well. Lower estrogen levels change the vaginal environment in ways that make it easier for harmful bacteria to thrive. People with conditions that prevent the bladder from emptying fully, those who use catheters, and anyone with a suppressed immune system are also more vulnerable.
Preventing Recurrent UTIs
If you get UTIs repeatedly, several evidence-based strategies can help reduce how often they come back.
Cranberry Products
Cranberry supplements and juice have genuine preventive value, not just folklore. The American Urological Association recommends cranberry as an option for women with recurrent UTIs. The key is getting enough of the active compound: supplements standardized to at least 36 mg of proanthocyanidins (PACs) are more effective than lower-dose products. A 2024 analysis of over 3,000 participants across 20 trials found that cranberry juice reduced UTI rates by 54% compared to no treatment.
Drinking More Water
If your daily fluid intake is below about 50 ounces (1.5 liters), increasing it can make a meaningful difference. In one trial, women who boosted their water intake above that threshold had roughly half as many UTI episodes over a year compared to women who didn’t change their habits (1.7 versus 3.2 episodes). They also went much longer between infections: about 143 days versus 84.
Vaginal Estrogen
For perimenopausal and postmenopausal women, vaginal estrogen therapy is one of the more effective prevention strategies. It restores the vaginal environment to a state that supports protective bacteria and makes it harder for UTI-causing organisms to take hold. This is a topical treatment, not the same as systemic hormone therapy.
D-Mannose
D-mannose, a sugar supplement widely marketed for UTI prevention, has not held up well in rigorous testing. A large randomized trial of nearly 600 women found no difference in UTI recurrence between those taking 2 grams of D-mannose daily and those taking a placebo.
Contraception Changes
If you use spermicides or certain barrier methods and get frequent UTIs, switching to a different form of contraception may help by allowing your vaginal microbiome to maintain its natural protective balance.