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If you notice a foul smell coming from your urine, you may be concerned that it’s an early warning sign of cancer. You can rest assured that cancer is not the reason your urine has a bad odor.

The smell of urine is affected by factors ranging from what you eat to medical conditions you may have.

Several types of cancer have been found to alter the scent of urine. However, the human nose cannot detect cancer from urine’s smell.

Foul-smelling urine is not a symptom of cancer.

Studies indicate that cancer does emit a specific smell. This smell may be detected by dogs, who are trained specifically for this task. The human nose, however, cannot pick up the scent of cancer in urine.

If you notice a change in your urine’s smell, such as a foul, sulfur-like odor, it does not mean you have cancer.

The smell of urine can, however, signal other health concerns. We’ll discuss the urine smells associated with certain conditions such as diabetes or urinary tract infections.

Your kidneys clean your blood of toxins and waste products by turning them into urine. Urine is comprised of toxins and compounds, such as urea, creatinine, salt, and uric acid.

If you drink lots of water, these substances are sufficiently diluted enough to not emit much of a smell. The more concentrated your urine is, the stronger its scent may be.

Other factors that can alter urine’s smell include certain health conditions, eating or drinking particular foods and liquids, and taking medications and supplements.


Not taking in enough fluid is a common cause of foul-smelling urine. When you’re dehydrated, your urine may smell strongly of sulfur, or ammonia. Urine contains byproducts and chemicals, which emit a bad smell, when they’re not diluted sufficiently.


Uncontrolled diabetes may make urine take on a sweet or fruity smell. This is caused by excess glucose circulating through the blood and urinary tract. For some people, sweet-smelling urine may be their first symptom of diabetes.

Urinary tract infection (UTI)

A bacterial infection in the urinary tract can cause urine to take on a strong, unpleasant smell. Bacterial infections occur in the bladder, kidneys, urethra, or ureters. UTIs can cause pain upon urination. They also darken urine, or make it appear cloudy. In some instances, you may see blood in your urine.

Bacterial vaginosis

Some vaginal infections, such as bacterial vaginosis, can give vaginal discharge a fishy smell. This smell is not caused by a change in urine but rather by the release of vaginal fluids during urination.


This common sexually transmitted infection (STI) is caused by a parasite. Like bacterial vaginosis, trichomoniasis can alter the scent of vaginal discharge, making urine smell fishy.


You may think it’s an urban myth, but eating asparagus can cause urine to smell like sulfur. Asparagus contains asparagusic acid, a sulfurous compound which gets excreted out in urine.

Vegetables in the Allium species also contain sulfur, and may alter urine smell in some people. They include:

  • onions
  • garlic
  • scallions
  • shallots

Medications and supplements

Sulfa drugs may make urine smell like sulfur. These drugs are used to treat multiple conditions, including diabetes and rheumatoid arthritis. They include:

  • glyburide
  • sulfasalazine
  • sulfonamide antibiotics

Supplements such as vitamin B6 (thiamine) may give urine a fishy smell, especially if you take more than the recommended amount.

Early detection of cancer has been proven to save lives and decrease suffering. For that reason, scientists and researchers are always looking for innovative, noninvasive ways to sleuth out cancer in its earliest stages.

Even though human noses can’t smell it, research indicates that cancer emits a distinctive scent. The exact reason for this is not yet known. It is thought that cancer’s smell may be caused by elevated levels of bad-smelling molecules called polyamines, or by other cancer-specific volatile organic compounds.

Studies have found that dogs can be trained to sniff out certain types of cancer through urine, feces, breath, and tumorous tissue. Cancers that can be detected by canine noses include:

Electronic nose technology that utilizes chemical sensors are also being studied as potential, noninvasive diagnostic tools for early detection of cancer and other diseases.

If your urine smell changes suddenly and you’re concerned, contact your doctor. Sweet-smelling urine may signal diabetes, and should always be assessed medically.

Call your doctor if foul-smelling urine is accompanied by any of these symptoms:

  • fever
  • blood in urine
  • cloudy urine
  • pain or burning during urination
  • abdominal or lower back pain
  • pelvic pain or pressure
  • vaginal itching

Foul-smelling urine is not a symptom or sign of cancer. It can, however, indicate other conditions, such as urinary tract infections or STIs.

Even though people can’t detect it, cancer has been found in studies to have a specific smell.

Dogs have been trained to sniff out cancer in urine, feces, breath, and human tissue.

Electronic noses are also being developed which may be able to noninvasively detect cancer in its earliest stages.