Cloudy or smelly urine: causes, red flags and when to get it checked

Urine contains water, waste products, salts and cells. When more concentrated, or when it contains white cells, bacteria, mucus, crystals or protein, it looks cloudy and may smell stronger. Appearance alone is a poor guide to infection, so symptoms and a urine test matter more.

• Dehydration and concentrated urine, particularly in the morning or hot weather.

• Foods and supplements: asparagus, garlic, coffee, B vitamins, and some medicines such as antibiotics.

• Urinary tract infection: cloudy, offensive urine with burning, frequency, urgency and lower abdominal pain.

• Vaginal discharge or contamination of the sample in women, which can make urine appear cloudy.

• Phosphate crystals and kidney stones, which can cloud urine and cause pain or blood.

• Sexually transmitted infections causing urethral discharge and cloudiness.

• Protein or white cells from kidney disease, and prostate infection in men.

• Rarely, bladder fistula (a connection to the bowel or vagina) with air or faecal smell and recurrent infection.

Fever or shaking chills, loin pain, vomiting, blood in the urine, confusion or sudden deterioration in an older person, pregnancy, diabetes, a catheter, recurrent infections, or air bubbles or faecal matter in urine need prompt review.

• Call 999 or go to A&E: cloudy urine with fever, rigors, confusion or collapse, particularly in older people.

• Same-day GP or NHS 111: loin pain, fever, vomiting or urinary symptoms in pregnancy or men.

• GP within a day or two: burning and frequency with cloudy urine, or recurrent symptoms.

• Routine: cloudy urine without symptoms that clears with fluids.

The doctor asks about burning, frequency, urgency, pain, fever, blood, discharge, sexual history, pregnancy, diabetes, catheter use, diet and fluids. They examine the abdomen and loins and may check for vaginal or penile discharge.

• Urine dipstick: leukocytes, nitrites, protein and blood.

• Urine culture: to identify bacteria and guide antibiotics in complicated or recurrent cases.

• Blood tests: inflammatory markers and kidney function if unwell.

• STI screening if discharge or risk exposure.

• Kidney and bladder ultrasound or CT: for recurrent infection, stones or structural problems.

Drink plenty of fluids, empty the bladder fully and urinate after sex. For women, wipe from front to back. A pharmacist can advise on pain relief and symptoms. If urine infection is likely, a prescription may be needed and antibiotics should be completed. Cranberry products have limited evidence.

The NHS route is a pharmacy or GP; some pharmacies can supply treatment for uncomplicated infections in women. Private GP and urology services provide direct access to urine cultures and imaging.