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Bladder Infection Causes, Signs & Symptoms

Written by Puya Yazdi, MD | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:
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SelfDecode Science Team | Written by Puya Yazdi, MD | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Bladder infection

A bladder infection is a common type of UTI, especially among women. This bacterial infection can be painful, stubborn, and distressing. Learn what can cause it and how to spot the symptoms.

What Is a Bladder Infection?

Overview & Prevalence

The bladder’s role is to collect and store urine that has been filtered by the kidneys. An infection occurs when bacteria reach the bladder and infect it, which causes frequent and painful urination. Bladder infections are the most common type of UTI (urinary tract infection), while UTIs are the most common type of bacterial infection in women [1].

Nearly half of all women will experience at least one UTI in their lifetime. UTIs can be stubborn and turn into a chronic problem. About 10% of women get an infection every year and almost half will have a second infection within a year [1, 2].

Women are about four times more likely to get a UTI than men. Bacteria from the stool can trigger an infection if they can reach the urethra, a tube that carries urine from the bladder to the place where it flushed from the body. Women have a shorter urethra, making it easier for bacteria to travel up to their bladder [2].

Although UTIs are most common in younger women, they can occur at any age. This is especially a concern in children, the elderly, and in pregnant women, in whom infections can cause other health complications [2].

A bladder infection is not sexually transmitted, although the two may have some similar symptoms (like painful urination). Although sexual activity increases the risk of UTIs in women, the infection is not contagious. Women with UTIs won’t transfer the infection to their sexual partners [3].

The infection is typically treated with a short course of antibiotics, while various natural remedies and lifestyle changes can reduce your risk of it coming back.

Bladder infection is extremely common, especially among women. It happens when bacteria invade the bladder and is not sexually transmitted.

Types of Infection

The first step in understanding bladder infections is differentiating them from other UTIs.

UTI (urinary tract infection) is an umbrella term for infections of the urinary tract, which includes the bladder, urethra, and kidneys.

Kidney infections are sometimes called an upper UTI. They are much more serious and require immediate medical care. Bladder infections are known as lower UTIs. This article mostly focuses on uncomplicated bladder infections. Uncomplicated UTIs are very common and occur in healthy, non-pregnant women.

On the other hand, a UTI is complicated when there is a risk of repeat infections or treatment failure. Complicated UTIs usually require longer antibiotic therapies and possibly other precautions. They involve [4]:

  • Men
  • Pregnant women
  • People with urinary tract abnormalities
  • Those with a suppressed immune system
  • Highly-resistant bacteria
  • People who use medical devices, including catheters and tubes
  • People with kidney transplants or kidney disease
The most common type of bladder infection is a simple UTI. It is different from upper and complicated UTIs, which require longer treatment and immediate medical care.

Bladder Infection Causes

Causes shown here are commonly associated with bladder infection. Work with your doctor or other health care professional for an accurate diagnosis.

Types of Bacteria that Cause Infection

Bladder infections can be caused by a variety of bacteria, but the most common type is E. coli, responsible for 90% of UTIs. E. coli is normally found in the gut [5].

Bladder infections usually start when fecal bacteria enter the urethra. From there, the bacteria move up the urinary tract until they reach the bladder and cause an infection. Women are more vulnerable because they have a shorter urethra, which reduces the distance the bacteria need to travel. If untreated, bacteria can continue up and cause a kidney infection [6].

Bacteria that cause bladder infections have cell structures that help them attach to the lining of the urinary system. This allows them to stick to the wall of the bladder and prevents the urine from washing them away. Some treatments work by blocking this attaching ability of bacteria [6].

Bladder Infection Signs & Symptoms

Bladder infection symptoms vary from person to person. If you experience anything out of the usual, see your doctor to get an accurate diagnosis and treatment.

Common Symptoms of Simple Infections

Bladder infections don’t always cause symptoms. However, if you’re a woman experiencing painful and frequent urination, you very likely have a UTI. We strongly recommend calling your doctor [7].

Symptoms of a bladder infection include [7]:

  • Pain, discomfort, or burning when urinating
  • Frequent or urgent urination
  • Lower abdominal and pelvic pain
  • Cloudy or bloody urine

Some women have no signs or symptoms, and such infections are usually not treated or tested for. Studies have revealed no negative long-term effects of asymptomatic UTIs [8, 7].

Complicated Infections

Complicated bladder infections and kidney infections can cause additional symptoms. If the bacteria continue to spread, the prostate and blood may also become infected.

Symptoms of a complicated bladder or kidney infection include [7+]:

  • Fever
  • Chills
  • Mental confusion
  • Back or side pain
  • Nausea and vomiting

Long-Term Risks

Recurrent bladder infections have been linked with an increased risk of bladder cancer in a study of almost 2,000 bladder cancer patients. A history of three or more bladder infections was also strongly associated with cancer. This does not mean that bladder infections will cause cancer, as many other underlying factors can increase the risk of both [9, 10].

What’s more, a review of 16 studies concluded that no such link exists in high-quality studies [11].


Simple bladder infections are often mild and respond quickly to antibiotics. However, certain populations will require special treatment and additional precautions.

Risk Factors for Bladder Infection


Many factors may increase your risk of developing a bladder infection. Female anatomy is the main one and some risk factors are specific to women. For example, studies consistently show that sexual activity is the strongest risk factor in women. Using spermicides as birth control and a family history of UTIs are two others. Together, they can nearly double the risk of infection [3, 12].

Overall, the risk factors for bladder infections include [13]:

  • Sexual activity (in women)
  • New sex partner (in women)
  • Use of spermicide birth control (in women)
  • Mother with a history of UTIs (in women)
  • Low estrogen (in postmenopausal women)
  • Age of first UTI at 15 years or younger
  • Conditions that reduce urine flow
  • Urinary or fecal incontinence
  • Urinary tract blockages
  • Diabetes
  • Being overweight
  • Suppressed immune system
  • Catheter use

Good intimate hygiene may reduce the risk of UTIs in young women and in pregnant women. Urinating after sex was also found to reduce the rate of UTIs in some studies, but not others. However, the research also shows that many practices commonly believed to prevent chronic, recurrent bladder infections may have no effect at all [14, 15, 16, 3].

Factors that are NOT linked to recurrent bladder infections in women with frequent UTIs include [3]:

  • Wiping pattern
  • Hot tub use
  • Douching
  • Tampon use
  • Type of underwear/tights
  • Blood type


Pregnant women have a higher risk of developing bladder and kidney infections. This is due to physical changes in the urinary tract caused by pregnancy [17].

All bladder infections are considered complicated in pregnancy, as the risk of serious complications is increased. Complications include high blood pressure in the mother, premature birth, and low birth weight [18, 19, 20].

Pregnant women have an increased risk of symptom-free bladder infections, which are often not a concern in non-pregnant women and go untreated. In pregnant women, these infections are more likely to progress to the kidneys. For this reason, it is important for pregnant women to test for infections even if they do not have symptoms [17].

Research shows that antibiotic treatment is important for preventing serious pregnancy complications in women with an infection. However, many commonly used antibiotics may cause defects in newborns. The usual first choices are safer penicillin-like antibiotics [17, 21].

Pregnant women are at an increased risk of bladder infection, which requires special management to avoid complications.


Children can also get bladder infections, which are often harder to spot because the symptoms are not specific. Symptoms in children include fever, irritability, and vomiting [7].

Serious bladder infections in children can lead to kidney scarring, which can reduce the kidneys’ ability to properly filter blood [22, 23, 24, 25].

It is extremely important to take your child to a doctor if they display nonspecific symptoms of illness for more than three days, or if a fever reaches 100.4 degrees (for babies under 3 months) or 104 degrees (for children).


Bladder infections are among the most common bacterial infections in the world. They affect almost half of all women at one point in their life. For many, they are a recurring problem. The most notable symptoms are urinating more often, accompanied by a burning sensation.

Bladder infections in pregnant women, men, or children can be more serious and require additional precautions. Sexual activity, a family history of infection, and the use of spermicides are most strongly linked to bladder infections in women.

Further Reading

About the Author

Puya Yazdi

Puya Yazdi

Dr. Puya Yazdi is a physician-scientist with 14+ years of experience in clinical medicine, life sciences, biotechnology, and nutraceuticals.
As a physician-scientist with expertise in genomics, biotechnology, and nutraceuticals, he has made it his mission to bring precision medicine to the bedside and help transform healthcare in the 21st century. He received his undergraduate education at the University of California at Irvine, a Medical Doctorate from the University of Southern California, and was a Resident Physician at Stanford University. He then proceeded to serve as a Clinical Fellow of The California Institute of Regenerative Medicine at The University of California at Irvine, where he conducted research of stem cells, epigenetics, and genomics. He was also a Medical Director for Cyvex Nutrition before serving as president of Systomic Health, a biotechnology consulting agency, where he served as an expert on genomics and other high-throughput technologies. His previous clients include Allergan, Caladrius Biosciences, and Omega Protein. He has a history of peer-reviewed publications, intellectual property discoveries (patents, etc.), clinical trial design, and a thorough knowledge of the regulatory landscape in biotechnology. He is leading our entire scientific and medical team in order to ensure accuracy and scientific validity of our content and products.


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