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What Causes Bad Smelling Urine?

Urine could smell foul, strong, or sweet. The most common causes of bad smelling urine are dehydration, dietary changes, a side-effect of medication, or a urinary tract infection. Less common causes are other infections, high blood sugar, or liver damage.
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Last updated April 18, 2024

Bad smelling urine quiz

Take a quiz to find out what's causing your bad smelling urine.

Bad smelling urine quiz

Take a quiz to find out what's causing your bad smelling urine.

Take bad smelling urine quiz

Common urine odor symptoms

Urine is meant to have a mild odor. If you are well-hydrated, urine may not smell like anything, or it may take on the aroma of something you ate or drank, like asparagus or coffee. A strong, undesirable smell, especially if it keeps occurring, can be a sign of illness.

What does bad smelling urine mean?

“Foul-smelling urine can come from many sources, often a bladder infection. If you notice a sudden change in the smell of your urine, it may be due to foods or vitamins (e.g. B vitamins). However, a change in the smell of urine (or the appearance) is a hint that you may have a bladder infection. This infection can be due to improper hygiene, catheterizations, kidney stones, or anything that keeps you from completely emptying your bladder.”—Dr. Jeffrey M. Rothschild

Common characteristics of bad smelling urine

If you're experiencing bad smelling urine, it can take on the following characteristics.

  • An ammonia smell
  • An overly sweet, almost sugary smell
  • A musty smell
  • A foul smell
  • A sulfurous smell

Duration of bad smelling urine

How long bad smelling urine lasts depends on the cause.

  • Temporary: A bout of bad or foul-smelling urine will resolve quickly if it's due to foods or drinks. It may last days if due to an infection.
  • Persistent: Conditions like diabetes or liver failure may cause bad smelling urine that last weeks or months if not treated.

Who is most often affected?

The following people are more likely to experience bad smelling urine.

  • Anyone who regularly eats pungent foods, like asparagus
  • People who take vitamin B6 or some medications
  • Sexually active and older women: UTIs are more likely among these women.
  • Anyone with diabetes or liver or kidney failure
  • People who are dehydrated or wake up dehydrated

Is bad or foul-smelling urine serious?

The severity of your bad smelling urine depends on the cause.

  • Not serious: Any changes in urine smell are often due to dehydration, eating certain foods, or starting a new supplement or medication. If you have no other symptoms, it's rarely a concern.
  • Moderately serious: If there is also an unusual color to the urine, along with a persistent and very disagreeable odor, you may have a condition that should be treated.
  • Serious: If you have the above signs along with pain or other symptoms of illness, you should see your medical provider as soon as possible.

What causes bad smelling urine with no other symptoms?

“Eating certain foods can change the smell of urine and cause "bad smelling urine." Asparagus is a common culprit. So is coffee. Usually, foul-smelling urine is associated with infections and can happen in the absence of other symptoms. You may also have bladder pain and possibly fever or chills. Dehydration and concentration of urine can also increase the intensity of the smell of urine.”—Dr. Rothschild

Why your urine smells

Many conditions can have bad or foul-smelling urine as a symptom. The following details may help you better understand your symptoms and if and when you need to see a physician.

Urinary tract infection

A urinary tract infection, or UTI, can involve any or all parts of the urinary system but most often affects the bladder and urethra.

Bacteria from the gastrointestinal tract – especially Escherichia coli (E. coli) – are the most common cause of UTIs. These bacteria spread from the anus to the urethra. Sexual activity can do this, but a UTI is not considered a sexually transmitted disease.

Women are more at risk for UTI than men. Due to female anatomy, the urethral opening is a short distance from the anus. Anyone who uses catheters to urinate is also prone to UTIs.

Common symptoms of less-serious UTIs include lower abdominal discomfort and pressure; burning or discomfort on urination; and cloudy or discolored urine.

Left untreated, the infection could spread to the kidneys and cause a medical emergency.

Diagnosis is made by having the patient describe the symptoms and by testing a urine sample for bacteria.

UTIs are caused by bacteria and so can be treated with antibiotics.

Prevention involves good hygiene and drinking plenty of water.

Kidney infection (pyelonephritis)

A kidney infection, or pyelonephritis, is actually a type of urinary tract infection (UTI) that begins in the urethra or bladder and spreads to the kidneys.

The infection is caused by bacteria that either travel into the urethra or spread from an infection elsewhere in the body.

Women, especially pregnant women, are most susceptible. Anyone who has had a urinary tract blockage, or uses a catheter, or has a weakened immune system is also at risk for a kidney infection.

Symptoms include fever; chills; back and abdominal pain; and frequent, painful urination. If there is also nausea and vomiting and discolored, foul-smelling urine, take the patient to the emergency room or call 9-1-1.

Left untreated, pyelonephritis can cause permanent damage to the kidneys. Bacteria can also enter the bloodstream and cause a life-threatening infection elsewhere in the body.

Diagnosis is made through urine test, blood test, and sometimes imaging such as ultrasound, CT scan, or x-ray.

Treatment includes antibiotics and sometimes hospitalization.


Dehydration means the body does not have enough water to carry out its normal processes.

Most susceptible to serious dehydration are young children with fever, vomiting, and diarrhea. In adults, some medications increase urination and can lead to . Anyone exercising vigorously, especially in hot weather, can quickly become dehydrated.

Symptoms include extreme thirst; dry mouth; infrequent, dark-colored urine; dizziness; and confusion. Young children may have sunken eyes, cheeks, and soft spot on top of the skull.

Severe dehydration is a serious medical emergency that can lead to heat stroke, kidney damage, seizures, coma, and death. Take the patient to the emergency room or call 9-1-1.

Diagnosis is made through blood tests and urine tests.

Mild dehydration can be treated simply by drinking extra water, or water with electrolytes such as sports drinks. More serious cases may be hospitalized for intravenous fluids.

It's important for anyone who is outside in hot weather, or who is ill, to drink extra fluids even before feeling thirsty as thirst is not always a reliable guide.

Chronic kidney disease

Chronic kidney disease is a general term for kidney damage caused over time by other illnesses, especially high blood pressure and diabetes. Eventually kidney function becomes impaired and wastes are no longer properly filtered from the blood, leading to serious illness.

Most susceptible are those over age 50 with high blood pressure, diabetes, obesity, and/or a family history of kidney disease.

Symptoms include fatigue; difficulty concentrating; poor appetite; muscle cramps at night; dry, itchy skin; swollen eyes, feet, and ankles; and increased urination.

Left untreated, chronic kidney disease results in serious illness, kidney failure, and death. It is important to see a medical provider as soon as symptoms begin.

Diagnosis is made through physical examination; a blood test called Glomerular Filtration Rate (GFR;) ultrasound or CT scan of the kidneys; and sometimes a kidney biopsy.

Treatment includes medications for high blood pressure, high cholesterol, and fluid retention, and a low-protein diet to reduce the work the kidneys must do. Dialysis and kidney transplant are only done if there is kidney failure.

Bacterial vaginosis

Bacterial vaginosis is an inflammation of the vagina due to overgrowth of the bacteria which are normally present.

It is not considered an STD (sexually transmitted disease) but nearly all cases are found in women after unprotected sexual contact, especially with multiple partners.

Frequent douching is also a factor.

Male partners do not carry this condition, but it can spread between female partners.

Common symptoms include an itchy, foul-smelling discharge that may look grayish or greenish, as well as burning during urination. However, some women have no symptoms.

The greatest risks of bacterial vaginosis are secondary. The symptoms can be similar to actual STDs and so should not be ignored. This condition makes a woman more vulnerable to actual STDs, as well as to pelvic inflammatory disease and to infections following any gynecologic surgery.

Pregnant women with bacterial vaginosis are at risk for premature or low-birth-weight babies.

Diagnosis is made through symptoms, and/or pelvic exam and vaginal swab.

Treatment consists of oral medication, and sometimes a cream or gel that is inserted into the vagina.

Food, supplements, and medication causes

Food or medication can cause bad smelling urine.

  • Asparagus: This vegetable is a well-known offender when it comes to causing a strong smell to the urine, due to its high sulfur content.
  • Garlic, onions, leafy vegetables, and eggs: These foods all contain sulfur, but like asparagus, they are good for you, and there is no need to avoid them. Any smell they give to the urine is harmless.
  • Vitamin B6: Also called pyridoxine, this may cause a strong smell to the urine from doses that exceed 10 mg per day.

Medical causes

Medical conditions can cause bad smelling urine.

  • Bacterial infection: Inflammation of any part of the urinary tract can give urine a foul smell.
  • High blood sugar: This condition causes a strong, sweet smell to the urine.
  • Liver damage: This condition causes a sweet, musty smell of both the breath and the urine because toxins are not properly filtered out of the blood.

This list does not constitute medical advice and may not accurately represent what you have.

Non-specific change in urine

Urine is the product of the kidneys filtering the blood from waste products and excess water. Depending on what you eat, the color and odor of your urine can change. Beets are known to turn urine pink or red, which can be mistaken for blood. Asparagus sometimes gives a distinctive smell. Medication can also change smell and color of your urine.

Rarity: Common

Top Symptoms: a change in either color of odor of urine, frequent urination

Symptoms that always occur with non-specific change in urine: a change in either color of odor of urine

Symptoms that never occur with non-specific change in urine: painful urination, bright red (bloody) urine, fever, frequent urination

Urgency: Wait and watch

When and how to treat smelly urine

When it is an emergency

Seek immediate treatment for bad smelling urine if you experience the following.

  • You have extreme fatigue, ongoing thirst, and increased urination: Along with a strangely sweet smell to the urine
  • You have back pain: Along with chills, fever, and foul-smelling urine that looks pink or red
  • You have ongoing fatigue with yellowing of the skin and eyes (jaundice): Along with swollen ankles, and a musty smell to the urine and breath.

Can bad smelling urine be an STD?

“Foul-smelling urine can be due to an STD, also known as a sexually transmitted infection (STI). Trichomonas can cause vaginal discharge that has a fishy odor. A urinary tract infection (UTI) can cause pus within the urine that may be pungent and foul-smelling.“—Dr. Rothschild

When to see a doctor

Schedule an appointment if you experience the following.

  • You are on a diuretic medication and have bad-smelling urine: Your physician may change or adjust the dosage of the diuretic.
  • You have lower abdominal pain with foul-smelling urine
  • You have foul-smelling urine and urinary urgency or frequency

At-home treatments

You can try the following treatments at home.

  • Drink more water on a regular basis
  • Take vitamin C tablets
  • Drink green tea
  • Drink unsweetened cranberry juice or take over-the-counter cranberry concentrate tablets: Do not use cranberry products if you've had a kidney stone or you are taking a blood-thinning medication (an anticoagulant).

FAQs about bad smelling urine

Can pregnancy cause bad smelling urine?

Yes. Pregnancy can increase the chances of a bladder infection because the gravid (pregnant) uterus can change the ability of the bladder to empty sufficiently. The bladder with urine in it for a long time can allow bacteria to grow and produce foul-smelling urine. If this happens, it should be treated immediately.

Is foul smelling urine a sign of dehydration?

Dehydration may increase the concentration of your urine. Urine is also often darker. Foul-smelling urine is different than urine that smells stronger. The color may change from yellow to orange or cloudy or red. These changes may signal a urinary tract infection (UTI) or a sexually transmitted infection (STI), which requires medical attention.

Questions your doctor may ask about bad smelling urine

  • Do you feel pain when you urinate?
  • Have you noticed any changes in the color of your urine recently?
  • Any fever today or during the last week?
  • Have you ever had a urinary tract infection?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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