Urinary Tract Infection
Symptoms, Causes & Treatment
Everything you need to know about UTIs: What causes them, how to recognise the symptoms, and possible treatment.
What Is a Urinary Tract Infection?
A urinary tract infection (UTI) is a bacterial infection affecting any part of the urinary system, which includes the urethra, bladder, ureters, and kidneys. The vast majority of UTIs are lower urinary tract infections confined to the bladder (cystitis) or urethra. Upper urinary tract infections involving the kidneys (pyelonephritis) are less common but more serious.
UTIs are among the most frequently encountered bacterial infections in clinical practice. In the UK, around one in two women will experience at least one UTI during their lifetime, with many experiencing recurrent episodes. Men are significantly less susceptible due to anatomical differences, though UTIs do occur and are treated as complicated infections requiring further assessment.
Bacterial UTIs are caused predominantly by Escherichia coli (E. coli), a bacterium normally present in the gastrointestinal tract that can migrate to the urinary tract. Other causative organisms include Klebsiella pneumoniae, Staphylococcus saprophyticus, and Proteus mirabilis.
UTIs respond well to antibiotic treatment when identified promptly. Most uncomplicated lower UTIs resolve within a few days of appropriate therapy. Delayed treatment can allow infection to spread to the kidneys, resulting in a more serious illness.
A UTI requires a clinician-led assessment and a prescription-only antibiotic. Treatment can now be accessed quickly and conveniently through an online consultation with a licensed clinician.
What Are the Symptoms of a UTI?
Symptoms vary depending on which part of the urinary tract is affected and the severity of the infection.
- Burning or stinging when urinating (dysuria)
- Needing to urinate more often than usual
- Sudden, urgent need to urinate
- Cloudy or dark-coloured urine
- Strong or unpleasant-smelling urine
- Blood in the urine (haematuria)
- Pelvic pain or pressure (particularly in women)
- High fever (typically above 38°C) with chills
- Pain in the loin or flank (side of the back)
- Nausea and vomiting
- Significant fatigue and malaise
- Lower UTI symptoms may also be present
In older people, classic UTI symptoms may be absent. A UTI may instead present as sudden-onset confusion, agitation, increased falls, or unexplained deterioration in physical or cognitive function. Any acute unexplained change in an older person warrants clinical assessment to exclude a UTI.
What Causes a UTI?
UTIs occur when bacteria – most commonly E. coli from the bowel – enter the urinary tract via the urethra and begin to multiply. Because the female urethra is significantly shorter and anatomically closer to the anal region, bacteria can more easily reach the bladder in women, which explains the much higher prevalence of UTIs among females.
E. coli from skin, bowel, or vaginal flora migrates into the urethra – the most common cause.
Intercourse can introduce bacteria into the urinary tract, strongly associated with UTIs in sexually active women.
Urinary catheters bypass natural defences, providing a direct route for bacterial entry.
Kidney stones or structural problems impair normal urine flow, creating conditions that favour bacterial growth.
In men, BPH causes incomplete bladder emptying, increasing susceptibility to infection.
Elevated urinary glucose provides a growth medium for bacteria; neuropathy may also impair bladder emptying.
Key Risk Factors
How Is a UTI Diagnosed?
A UTI is typically diagnosed through a combination of symptom assessment and urine testing. For uncomplicated UTIs in otherwise healthy, non-pregnant women with classic symptoms, UK clinical guidelines (NICE) support empirical antibiotic treatment without laboratory testing, though urine testing may still be performed to confirm the diagnosis or identify the causative organism.
How Is a UTI Treated?
The cornerstone of UTI treatment is a course of antibiotics prescribed by a licensed clinician. The choice of antibiotic, dose, and duration depends on the type and severity of the infection, your medical history, and local antibiotic resistance patterns.
Supportive Measures
Alongside antibiotics, staying well hydrated (aim for around 2–3 litres of water per day) helps flush bacteria from the urinary tract. Paracetamol or ibuprofen can manage pelvic pain and fever. Over-the-counter urinary alkalinising sachets (e.g. sodium citrate) can ease the burning sensation but do not treat the infection itself.
Recurrent UTIs
Defined as two or more infections within six months, or three or more within twelve months. Management options include self-start antibiotic therapy, low-dose nightly prophylaxis, post-coital prophylaxis, D-mannose supplementation, methenamine hippurate, and topical oestrogen in postmenopausal women.
When Should You Seek Medical Advice for a UTI?
You have a high fever with confusion or severe loin pain · You are unable to keep fluids down and feel critically unwell · A child under 3 months has any signs of infection.
Symptoms are severe, worsening, or not improving after 48 hours of antibiotics · You develop fever, chills, or loin pain suggesting kidney involvement · You are pregnant · You are a man with UTI symptoms · You are a child · You have diabetes, kidney disease, or a weakened immune system · You are experiencing recurrent UTIs.
How Can You Prevent UTIs?
While not all UTIs can be prevented, evidence-based lifestyle measures can meaningfully reduce the risk of recurrent infections.
Drinking sufficient water promotes regular urination, helping flush bacteria before they establish an infection.
Voiding promptly after intercourse clears bacteria that may have entered the urethra during sex.
Always wipe front to back after using the toilet to avoid transferring bacteria from the anal region.
Holding urine allows bacteria to multiply. Urinate regularly and fully empty the bladder each time.
Both may modestly reduce recurrence. Neither replaces antibiotic treatment for an active infection.
For postmenopausal women, vaginal oestrogen can restore protective vaginal flora and significantly reduce recurrence.
Speak to a Clinician About UTIs
Getting UTI treatment no longer means sitting in a waiting room. Through The GP Service, you can consult with a licensed clinician in minutes – from home, on your lunch break, or wherever works for you.
Expert clinical advice, when you need it.
UTI FAQs
Some very mild lower UTIs may resolve spontaneously, particularly in healthy, non-pregnant women with no risk factors. However, current UK clinical guidance does not recommend watchful waiting as a routine approach, because there is a real risk that an untreated infection will progress to the kidneys. For most people, a short course of antibiotics offers rapid symptom relief, confirmed eradication, and a significantly reduced risk of complications.
Many people notice a significant improvement within 24–48 hours of starting antibiotics, with burning and urinary urgency often easing within the first day. It is important to complete the full prescribed course even if you feel better sooner, to ensure the infection is fully eradicated and to reduce the risk of antibiotic resistance.
Signs that a lower UTI may have progressed to a kidney infection include fever (above 38°C), chills or rigors, pain in the loin or flank (the side of your back below the ribs), nausea, and vomiting. If you develop these symptoms, seek medical attention the same day.
Yes, though UTIs are considerably less common in men due to anatomical differences. When a man does develop a UTI, it is treated as a complicated infection – more likely to involve the prostate or kidneys – and requires thorough investigation to identify any underlying cause. Men with UTI symptoms should always be assessed by a clinician.
UTIs are not contagious in the conventional sense. They cannot be passed from person to person like a cold or flu. The bacteria that cause UTIs are normally present on the body, and certain activities can introduce them into the urinary tract. A UTI itself is not a sexually transmitted infection, though some STIs can produce similar symptoms.
Recurrent UTIs are common, particularly in women, and can be caused by anatomical susceptibility, sexual activity, postmenopausal hormonal changes, bladder emptying difficulties, or an underlying condition such as diabetes. If you experience two or more UTIs within six months, or three or more within twelve months, speak to a clinician about investigating possible causes and discussing prevention strategies.
In the UK, trimethoprim and nitrofurantoin (the most commonly prescribed UTI antibiotics) are prescription-only. Some pharmacies can issue prescriptions under a Patient Group Direction (PGD) scheme, but access is variable. Over-the-counter options such as sodium citrate sachets can ease the burning sensation but do not treat the infection. The most reliable care is through a clinician consultation.
A single, promptly treated UTI is very unlikely to cause lasting kidney damage in a healthy adult. However, repeated, severe, or untreated kidney infections can over time cause renal scarring, which may contribute to reduced kidney function or hypertension. This is a particular concern in young children. Prompt treatment and investigation of recurrent UTIs is therefore important.