Cystitis is caused by germs, most often bacteria. These germs enter the urethra and then the bladder and can cause an infection. The infection commonly develops in the bladder. It can also spread to the kidneys.

Most of the time, your body can get rid of these bacteria when you urinate. But, the bacteria can stick to the wall of the urethra or bladder, or grow so fast that some stay in the bladder.

Women tend to get infections more often than men. This happens because their urethra is shorter and closer to the anus. Women are more likely to get an infection after sexual intercourse. Using a diaphragm for birth control can also be a cause. Menopause also increases the risk for a urinary tract infection.

The following also increase your chances of having cystitis:

• A tube called a urinary catheter inserted in your bladder
• Blockage of the bladder or urethra
• Diabetes
• Enlarged prostate, narrowed urethra, or anything that blocks the flow of urine
• Loss of bowel control (bowel incontinence)
• Older age (most often in people who live in nursing homes)
• Pregnancy
• Problems fully emptying your bladder (urinary retention)
• Procedures that involve the urinary tract
• Staying still (immobile) for a long period of time (for example, when you are recovering from a hip fracture)

Most cases are caused by Escherichia coli (E coli). It is a type of bacteria found in the intestines.

The symptoms of a bladder infection include:

• Cloudy or bloody urine
• Strong or foul-smelling urine
• Low fever (most people will not have a fever)
• Pain or burning with urination
• Pressure or cramping in the lower middle abdomen or back
• Strong need to urinate often, even right after the bladder has been emptied

Often in an older person, mental changes or confusion are the only signs of a possible infection.

In many cases, a urine sample is collected to do the following tests:

• Urinalysis -- This test is done to look for white blood cells, red blood cells, bacteria, and to check for certain chemicals, such as nitrites in the urine. Most of the time, your health care provider can diagnose cystitis using a urinalysis.
• Urine culture -- A clean catch urine sample may be needed. This test is done to identify the bacteria in the urine and decide on the correct antibiotic. This is often not needed to start treatment of cystitis.

Antibiotics can be taken by mouth. These are most often given to stop the infection from spreading to the kidneys.

For a simple bladder infection, you will take antibiotics for 1 to 5 days (women) or 7 to 14 days (men). The length of treatment depends on the antibiotic used.

For a bladder infection with complications such as pregnancy, diabetes, or a mild kidney infection, you will most often take antibiotics for 7 to 14 days.

It is important that you finish all the antibiotics prescribed. Finish them even if you feel better before the end of your treatment. If you do not finish the antibiotics, you may develop an infection that is harder to treat.

Let your provider know if you are or may be pregnant.

Your provider may prescribe medicines to ease discomfort. Phenazopyridine hydrochloride (Pyridium) is the most common of this type of medicine. You will still need to take antibiotics.

Everyone with a bladder infection should drink plenty of water.

Some women have repeat bladder infections. Your provider may suggest treatments such as:

• Taking a single dose of an antibiotic after sexual contact. These may prevent sexually transmitted infections.
• Keeping a 3-day course of antibiotics. These will be given based on your symptoms.
• Taking a single, daily dose of an antibiotic. This dose will prevent infections.

Over-the-counter products that increase acid in the urine, such as ascorbic acid or cranberry juice, may be recommended. These medicines may lower the concentration of bacteria in the urine.

Follow-up may include urine tests or cultures. These tests will make sure the bacterial infection is gone.

Lifestyle changes may help prevent some urinary tract infections.

Most cases of cystitis are uncomfortable, but go away without complications after treatment.

Contact your provider if you:

• Have symptoms of cystitis
• Have already been diagnosed and symptoms get worse
• Develop new symptoms such as fever, back pain, stomach pain, or vomiting

Uncomplicated urinary tract infection; UTI - acute cystitis; Acute bladder infection; Acute bacterial cystitis

Cooper KL, Badalato GM, Rutman MP. Infections of the urinary tract. In: Partin AW, Dmochowski RR, Kavoussi LR, Peters CA, eds. Campbell-Walsh-Wein Urology. 12th ed. Philadelphia, PA: Elsevier; 2021:chap 55.

Drekonja D. Approach to the patient with urinary tract infection. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 263.

Sobel JD, Brown P. Urinary tract infections. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 72.

Updated by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.