Urinary Tract Infection (UTI): Symptoms, Treatment, Prevention and When It Is Serious

A urinary tract infection (UTI) is an infection of any part of the urinary system: the bladder (cystitis), urethra, or the kidneys (pyelonephritis). Most are caused by bacteria from the bowel, especially E. coli, entering the urethra. UTIs are very common, particularly in women, with around half of all women having at least one in their lifetime. They are usually easily treated, but they can become serious if the kidneys are involved.

Symptoms

Bladder infection (lower UTI):

• Burning or pain when passing urine
• Frequent, urgent need to pass urine, often only a small amount
• Cloudy, dark or strong-smelling urine
• Blood in the urine (pink or red)
• Pain or pressure in the lower abdomen above the pubic bone
• Feeling that the bladder is not completely empty

Kidney infection (upper UTI), more serious:

• Fever and chills
• Pain in the flank or back, below the ribs, on one or both sides
• Nausea, vomiting
• Feeling very unwell, weakness
• Confusion in older adults

Children and babies: fever, irritability, poor feeding, vomiting or foul-smelling urine, without obvious symptoms. Any unexplained fever in a young child may need a urine test. See fever in children.

Older adults: may have only confusion, falls or reduced appetite.

Risk factors

• Female sex, and sexual activity
• Pregnancy
• Menopause (low oestrogen)
• Diabetes, particularly with poor sugar control. See early symptoms of diabetes
• Kidney stones or urinary obstruction, such as an enlarged prostate. See kidney stones
• Urinary catheters
• Weakened immunity, and some medicines (SGLT2 inhibitors carry a small risk of genital infections)
• Poor hygiene practices, delaying urination or not drinking enough
• Previous UTI
• Congenital urinary tract abnormalities in children

Diagnosis

• Urine dipstick for leucocytes and nitrites, and urine microscopy
• Urine culture to identify the bacteria and which antibiotics work, especially for recurrent infections, pregnancy, men, children and suspected kidney infection
• Blood tests in suspected kidney infection
• Ultrasound or CT in recurrent UTIs, men, children, or if stones or obstruction are suspected

Treatment

• Antibiotics for a few days for simple bladder infections in women (often 3-5 days, depending on the drug), and 7-14 days for kidney infections, men and complicated infections. The choice depends on local resistance and your health. Common options include nitrofurantoin, fosfomycin, trimethoprim, cefalexin, ciprofloxacin and others, as chosen by your doctor.
• Complete the course, even if symptoms improve.
• Do not use leftover antibiotics or buy them without prescription, because wrong or incomplete treatment promotes resistant bacteria and may mask serious infection.
• Pain relief: paracetamol. Avoid NSAIDs if you have kidney disease or could have dengue.
• Drink plenty of water to flush the bladder. Use our water intake calculator.
• Urinary alkalinisers (such as potassium citrate sachets) may ease burning, but should not replace antibiotics.
• Hospital treatment with IV antibiotics for severe infection, vomiting, pregnancy, sepsis, or inability to take tablets.

UTI in pregnancy

UTIs and even bacteria without symptoms in urine need treatment in pregnancy, because they raise the risk of kidney infection and premature labour. Pregnant women with UTI symptoms should see a doctor promptly. See early pregnancy symptoms.

UTI in men

UTIs are less common in men and often point to an underlying problem such as an enlarged prostate, stone or infection of the prostate. They need medical assessment and usually a longer course of antibiotics.

Prevention

• Drink enough fluids, enough that your urine is pale yellow.
• Do not hold urine for long. Empty your bladder when needed.
• Pass urine after sex, and wash genital area with water, avoiding perfumed soaps and douching.
• Wipe from front to back after using the toilet.
• Wear cotton underwear and avoid very tight clothing.
• Control diabetes and treat constipation.
• Cranberry products may reduce recurrences in some women, though evidence is inconsistent.
• Vaginal oestrogen helps postmenopausal women with recurrent UTIs.
• Low-dose preventive antibiotics, or methenamine hippurate, may be prescribed for frequent recurrences under specialist guidance.
• Remove or replace urinary catheters as soon as possible.

Recurrent UTIs

Two or more infections in six months, or three or more in a year, should be reviewed by a doctor to find causes and agree a prevention plan.

When to see a doctor

See a doctor if you have UTI symptoms that do not settle after a day or two, if you are pregnant, male, diabetic, a child, or elderly, or if you have had repeated infections.

Seek emergency care for fever with back or flank pain, vomiting, shivering, confusion, low blood pressure or inability to pass urine. These suggest kidney infection or sepsis.

References

• European Association of Urology: guidelines on urological infections
• NICE guideline NG109: urinary tract infection (lower), antimicrobial prescribing
• Infectious Diseases Society of America: guidelines on uncomplicated cystitis and pyelonephritis
• World Health Organization: antimicrobial resistance fact sheet