Urine that smells like sewer usually means a urinary tract infection or dehydration, but the cause depends on how long it has been happening and whether you have other symptoms
A urinary tract infection (UTI) is the most common reason urine develops a foul, sewer-like odor. When bacteria grow in your bladder or urethra, they produce compounds that give urine a strong, unpleasant smell — often described as ammonia-like or rotten. UTIs are more common in women than men, but anyone can get one.
Dehydration is the second most common cause. When you drink too little water, urine becomes more concentrated, and the natural compounds in it smell stronger. This is usually temporary and goes away once you drink more fluids.
Less often, sewer-like urine odor signals a metabolic disorder, a bladder or kidney stone, or a fistula (an abnormal connection between your bladder and bowel). These are less common but more serious, which is why the timing and your other symptoms matter.
Key Takeaways
- A urinary tract infection is the most likely cause, especially if you also feel pain or urgency when urinating.
- Dehydration concentrates urine and makes it smell stronger; drinking more water often fixes this within hours.
- If the smell persists for more than a few days, you have fever, back pain, or blood in your urine, contact your doctor.
- A urine culture test is the only way to confirm a UTI and determine which antibiotic will work.
- Some foods and medications can change urine odor, but sewer-like smell is not usually caused by diet alone.
How a urinary tract infection changes urine smell
Bacteria in your urinary tract break down compounds in urine and release ammonia and other gases. This is what creates the foul, sewer-like odor. The smell is often accompanied by other signs: pain or burning when you urinate, an urgent need to go frequently, cloudy or dark urine, and sometimes blood in the urine.
Women are more prone to UTIs because bacteria can travel up the urethra more easily due to its shorter length. Men can get UTIs too, though it is less common. Older adults, people with diabetes, and anyone with a catheter have higher risk.
A UTI does not always cause symptoms beyond the odor, especially in older adults. Some people notice only the smell change and assume it is dehydration. This is why it matters to pay attention to other signs and not wait too long before seeing a doctor if the smell does not improve.
Why dehydration makes urine smell stronger
Urine is mostly water mixed with waste products your kidneys filter from your blood. When you drink less water, the same amount of waste is dissolved in less liquid, making it more concentrated. Concentrated urine naturally smells stronger — the odor compounds are closer together.
This type of odor change is usually temporary. Drink a full glass of water and monitor your urine over the next few hours. If the smell fades and you feel normal otherwise, dehydration was likely the cause. If the smell persists or gets worse, or if you have pain or fever, something else is happening.
Certain situations increase dehydration risk: hot weather, exercise, vomiting, diarrhea, or straightforward forgetting to drink enough. People on diuretic medications (water pills) for blood pressure or heart conditions are also at higher risk.
Other medical causes of sewer-like urine odor
A bladder or kidney stone can trap bacteria and cause infection, leading to foul-smelling urine. Stones also cause sharp pain in your lower back or side, blood in urine, and difficulty urinating. Stones require imaging (ultrasound or CT scan) to diagnose and may need medical treatment to remove.
A fistula — an abnormal tunnel between your bladder and colon — allows stool bacteria to enter your urine. This is rare but causes persistent sewer-like smell, recurrent UTIs, and sometimes gas or stool in the urine. Fistulas are usually caused by inflammatory bowel disease, diverticulitis, or previous surgery and require imaging and surgery to repair.
Certain metabolic disorders, such as phenylketonuria (PKU) or other genetic conditions, can change urine odor. These are usually diagnosed in infancy through newborn screening, but if you have a known metabolic disorder and notice a new odor change, tell your doctor.
When to contact a doctor about urine odor
See a doctor if the sewer-like smell lasts more than a few days, even without other symptoms. Contact a doctor sooner if you have fever, pain in your lower back or side, pain or burning when urinating, blood in urine, or an urgent need to urinate frequently. These signs point to infection or another condition that needs treatment.
If you have diabetes, are pregnant, or are over 65, contact your doctor for any change in urine odor. These groups are at higher risk for serious UTIs that can spread to the kidneys or bloodstream if left untreated.
Call 911 or go to an emergency room if you have fever above 103°F, severe back or side pain, nausea and vomiting, or confusion along with the odor change. These can signal a kidney infection or sepsis, both of which need when ready care.
What your doctor will do to find the cause
Your doctor will ask when the smell started, what it smells like, and whether you have other symptoms. They will perform a urinalysis — a straightforward test where you provide a urine sample that is checked under a microscope and tested for bacteria, white blood cells, and blood.
If bacteria are found, your doctor will order a urine culture, which grows the bacteria in a lab to identify the exact type and test which antibiotics will kill it. This takes a few days but tells your doctor the most effective treatment. In the meantime, you may start antibiotics based on the urinalysis results.
If the urinalysis is normal but the smell persists, your doctor may order imaging (ultrasound or CT scan) to check for stones or other structural problems. Blood tests can also help rule out metabolic or kidney disorders.
How to reduce urine odor while waiting for diagnosis
Drink more water. This dilutes urine and reduces odor from any cause — infection, dehydration, or concentration of normal waste. Aim for enough water that your urine is pale yellow rather than dark. This is not a cure for infection, but it makes the symptom less noticeable and supports your kidneys.
Avoid foods and drinks that intensify urine odor, such as asparagus, garlic, onions, and caffeine. These do not cause sewer-like smell on their own, but they can make existing odor worse.
Do not delay seeing a doctor in hopes that hydration alone will fix the problem. If a UTI is the cause, you need antibiotics. Drinking water helps but does not kill the bacteria.
Frequently Asked Questions
Can a sewer smell in urine go away on its own?
If the cause is dehydration, yes — the smell usually fades within hours of drinking more water. If the cause is a UTI or other infection, the smell will not go away without treatment. Antibiotics are needed to kill the bacteria. Do not wait more than a few days to see a doctor.
Does sewer-like urine smell mean I have a serious infection?
Not necessarily. Most UTIs are uncomplicated and respond well to antibiotics. However, if the smell is accompanied by fever, severe pain, or blood in urine, the infection may have spread to your kidneys, which is more serious. This is why timing matters — see a doctor within a few days even if you feel otherwise well.
Can men get UTIs that cause this smell?
Yes, though it is less common. Men have a longer urethra, which makes it harder for bacteria to travel to the bladder. When men do get UTIs, they often have more severe symptoms, including fever and pain. Any man with sewer-like urine odor should see a doctor promptly.
Is sewer-like urine smell a sign of a fistula?
A fistula is rare and usually causes persistent sewer-like smell along with recurrent UTIs, gas in urine, or visible stool particles. If you have these signs, imaging tests can confirm it. Most people with sewer-like urine smell have a UTI or dehydration, not a fistula.
Can I treat a UTI at home without antibiotics?
No. Antibiotics are the only treatment that kills the bacteria causing a UTI. Drinking water, cranberry juice, and other home remedies may ease symptoms but do not cure the infection. Untreated UTIs can spread to your kidneys and become dangerous. See a doctor for a urine culture and prescription.