A bladder infection is a bacterial infection in the bladder, the organ that stores urine. It’s the most common type of urinary tract infection (UTI), and it happens when bacteria enter the urinary tract through the urethra and multiply inside the bladder. The vast majority of cases are caused by E. coli, a bacterium that normally lives in the gut but can easily migrate to the urinary opening. Bladder infections are extremely common, particularly in women, and most clear up quickly with a short course of antibiotics.
How Bacteria Reach the Bladder
The bladder is normally a sterile environment. Infection starts when bacteria from outside the body travel up the urethra, the tube that carries urine out. Because women have a much shorter urethra than men, bacteria have a shorter distance to travel, which is a major reason bladder infections are far more common in women.
Sexual activity is one of the most common triggers, because it can push bacteria toward or into the urethra. But you don’t need to be sexually active to get a bladder infection. The female genital area naturally harbors bacteria that can cause one. Other factors that raise your risk include using a catheter, having a blockage in the urinary tract (like a kidney stone), hormonal changes after menopause that thin the tissue lining the urethra, and anything that prevents you from fully emptying your bladder.
What a Bladder Infection Feels Like
The hallmark symptom is a burning sensation when you urinate. Most people also notice a persistent, urgent need to go, even when very little urine comes out. You may feel like you need to urinate every few minutes, which can be disruptive during the day and keep you awake at night.
Other common signs include:
- Pelvic pressure or discomfort in the lower belly, centered around the pubic bone
- Cloudy or strong-smelling urine
- Blood in the urine, which can make it look pink, red, or cola-colored
A bladder infection typically does not cause a fever. If you develop a high fever, chills, nausea, vomiting, or pain in your back or side, the infection may have traveled up to one or both kidneys. A kidney infection is more serious and needs prompt treatment.
How It’s Diagnosed
Diagnosis usually starts with a urine sample. A quick dipstick test in the office checks for two key markers. The first is leukocyte esterase, which signals the presence of white blood cells fighting an infection. The second is nitrites, which appear when certain bacteria (including E. coli) are present in significant numbers. If both markers are positive alongside your symptoms, the diagnosis is straightforward.
In some cases, particularly if you get bladder infections frequently or your symptoms are unusual, your provider may send the sample to a lab for a urine culture. This identifies the exact bacteria involved and which antibiotics will work against it, which is especially useful if a previous round of treatment didn’t help.
Treatment and Recovery Timeline
Uncomplicated bladder infections are treated with a short course of antibiotics. Treatment typically lasts three to five days, depending on the medication. Some options require only a single dose. Most people start feeling noticeably better within one to two days of starting treatment, though it’s important to finish the full course even after symptoms improve.
Over-the-counter pain relievers can help with the burning and pelvic discomfort while you wait for the antibiotic to take effect. Drinking plenty of water helps flush bacteria from the bladder, and urinating frequently rather than holding it in supports recovery.
Bladder Infection vs. Kidney Infection
A bladder infection stays in the lower urinary tract. It’s uncomfortable but rarely dangerous in otherwise healthy people. A kidney infection, called pyelonephritis, happens when bacteria travel from the bladder up the ureters and into one or both kidneys. This is a more serious condition that often begins as a simple bladder infection that wasn’t treated or didn’t respond to treatment.
The symptoms shift noticeably. Instead of just pelvic pressure and burning, you’ll typically develop pain in your back, side, or groin area, along with a high fever, shaking chills, nausea, and vomiting. A kidney infection requires more aggressive treatment and, in some cases, hospitalization. That shift in symptoms, particularly the combination of fever and flank pain, is the clearest signal that the infection has moved beyond the bladder.
Why Some People Get Repeated Infections
Some people deal with bladder infections once and never again. Others get them multiple times a year. Recurrent infections (generally defined as two or more within six months, or three or more in a year) are common in women and don’t necessarily mean something is structurally wrong. Factors like sexual frequency, use of spermicides, and postmenopausal hormonal changes all contribute to recurrence.
Practical steps that may reduce your risk include urinating soon after sex, staying well hydrated, and wiping front to back. These aren’t guaranteed to prevent every infection, but they reduce the opportunity for bacteria to reach the urethra.
Do Cranberry or D-Mannose Supplements Help?
Cranberry products and D-mannose supplements are widely marketed for UTI prevention. The theory behind both is that they stop bacteria from sticking to the bladder wall. However, the clinical evidence is underwhelming.
A large study tracked women taking D-mannose over six months and found no reduction in suspected UTIs, lab-confirmed UTIs, or hospital admissions compared to a control group. About 51% of women in the D-mannose group contacted a healthcare provider for a suspected infection, compared to 56% in the control group, a difference too small to be meaningful. Cranberry products have similarly thin evidence behind them, with health authorities noting little support for their use in preventing infections. Neither is harmful, but neither should replace proven treatments if you’re prone to recurrent infections.