14 Common Causes of Smelly Urine

2. Taking Certain Foods and Drinks

Your diet can influence how your urine smells, usually for a short time and without signaling any illness. Foods and drinks that contain strong natural oils or certain compounds can pass through your body and affect urine odor.

Asparagus is well known for causing a sharp, unusual smell soon after it is eaten. Coffee and certain spices can make urine smell stronger or more bitter, while fish- or onion-rich meals may have similar effects for some people. Low fluid intake can make urine more concentrated and intensify natural odors.

In addition to foods and drinks, some vitamin and mineral supplements, such as those containing vitamin B6, can temporarily change the color and odor of urine. These changes are harmless and usually fade once the body clears the excess nutrients.

3. Urinary Tract Infection (UTI)

A urinary tract infection (UTI) develops when bacteria enter and multiply within the urinary system, which includes the kidneys, bladder, ureters, and urethra. These bacteria often travel from the skin or rectum into the urethra, where the infection usually begins.

UTIs are common, especially in women due to a shorter urethra. Other risk factors include dehydration, sexual activity, pregnancy, poor hygiene, urinary blockages, and weakened immunity. Older adults and children may also be more vulnerable.

Common symptoms include strong or foul-smelling urine that may appear cloudy or darker. You may feel a burning sensation when urinating, frequent urges to urinate with only small amounts passed, or discomfort in the lower abdomen or back.

Diagnosis is confirmed through a urine test. Treatment typically involves antibiotics, and completing the full course helps prevent recurrence and complications. Without treatment, the infection can spread to the kidneys.

4. Yeast Infection

A yeast infection occurs when the fungus Candida grows excessively, often in warm, moist areas such as the vagina, mouth, or skin folds. With a vaginal yeast infection, you may notice a yeasty or bread-like odor that can mix with urine and create an unusual scent.

Other signs may include burning during urination and thick, white discharge. Yeast infections are different from urinary tract infections (UTIs), though they can occur at the same time. Antibiotics, hormonal shifts, tight clothing, poor hygiene, and uncontrolled diabetes can disrupt the body’s natural balance and increase the risk.

If odor changes persist or infections recur, a healthcare provider can confirm the cause. Treatment typically involves antifungal medication. Staying hydrated and keeping the genital area clean and dry may help lower the chance of recurrence.

5. Sexually Transmitted Infections (STIs)

Sexually transmitted infections (STIs) can affect both the urinary and reproductive systems. Irritation and bacterial growth in nearby tissues may change how urine smells, and odor changes can sometimes appear even before other clear symptoms. Common symptoms include burning during urination and unusual discharge.

Inflammation in the genital or urinary area can also affect how urine looks or smells. STIs commonly linked to these symptoms include chlamydia, gonorrhea, and trichomoniasis. These infections spread through sexual contact and can irritate surrounding tissues. Practicing safer sex, limiting sexual partners, and getting regular testing can help lower risk.

6. Kidney Stones

Kidney stones form when minerals and salts in the urine stick together and harden. This often happens when urine becomes too concentrated, allowing crystals to grow into stones. Common types include calcium, uric acid, and struvite stones, each forming for different reasons such as high acid levels, infection, or excess calcium in the urine.

Not drinking enough fluids, eating a high-protein or salty diet, and having a family history of kidney stones can increase your risk. Certain medical conditions that raise calcium or acid levels in the urine may also contribute. Kidney stones can affect how urine smells when they block the normal flow of urine or when infection develops around them. Trapped urine allows bacteria to multiply, which can change urine color and create a strong or ammonia-like odor. Smelly urine often appears along with other symptoms such as pain in the back or side, burning during urination, cloudy urine, or blood in the urine.

7. Diabetes

Diabetes can affect urine odor when the body does not use sugar properly. Excess glucose may spill into the urine, sometimes creating a sweet or fruity smell. You may also notice more frequent urination and increased thirst as the body works to remove extra sugar.

When blood sugar stays high for longer periods, urine can become more concentrated, which can intensify odor. Sweet-smelling urine can be an early sign of undiagnosed diabetes, especially if accompanied by fatigue, increased thirst, or blurred vision.

8. Vitamins

Some vitamins can affect how your urine smells. When your intake exceeds what your body needs, the excess is released through urine and may create a stronger or unusual odor.

Water-soluble vitamins such as vitamin C and most B vitamins move through the body quickly. This can cause urine to appear brighter yellow and smell stronger for a short time. Fat-soluble vitamins (A, D, E, and K) are stored in body fat and usually do not affect urine odor unless taken in very large amounts.

Vitamin B-complex supplements, especially vitamin B6, are commonly linked to noticeable odor changes. This effect is harmless and temporary Odor changes may be more noticeable if you take several supplements at once or if you are not drinking enough fluids. Drinking more water and staying within recommended daily limits often helps urine return to normal.

9. Taking Certain Medications

Some medications can change how your urine smells. As the body breaks down these drugs and removes them through the kidneys, byproducts can mix with urine and create stronger or unusual odors.

Certain drugs are more likely to cause noticeable changes. Sulfur-containing medications, including some antibiotics, may produce a rotten egg–like smell that usually fades after the medication is finished. Diuretics, or “water pills,” can also make urine smell stronger by increasing fluid loss, especially if hydration is low.

Vitamins and supplements are another common cause, particularly those containing vitamin B6, which can darken urine and affect its scent. Some pain relievers and additional antibiotics may also influence urine odor. These effects are generally harmless and often improve with increased fluid intake.

10. Liver Complications

The liver plays a key role in processing toxins and producing bile, which helps with fat digestion. When this process is disrupted, substances that should be removed from the body can build up in the blood and pass into the urine.

Conditions such as hepatitis, cirrhosis, or blockage of the bile ducts can interfere with normal liver function. As a result, waste products like bilirubin and urobilinogen may leak into the urine, affecting its color and smell. When this happens, urine may appear darker than usual and develop a musty or slightly sweet odor.

Changes in urine linked to liver problems often occur alongside other signs, such as tiredness or yellowing of the skin or eyes. If urine becomes noticeably darker or smells unusual for several days and you also feel unwell, this may indicate that the liver is under added stress.

11. You Might Be Pregnant

Stronger-smelling urine can sometimes occur during early pregnancy. Hormonal changes and shifts in how the body processes nutrients may affect urine odor, and you may also notice more frequent urination, especially at night.

Pregnancy can heighten the sense of smell, which can make ordinary scents seem stronger than usual. As a result, urine odor may feel more noticeable even when nothing else has changed. Dehydration can worsen urine odor because fluid needs increase during pregnancy. Drinking more water often helps lighten urine and reduce smell.

Prenatal vitamins, especially those containing iron and B vitamins, can also affect urine color and scent. This is common and usually harmless. If odor changes occur along with pain, burning, or cloudy urine, it may suggest a urinary tract infection.

12. Genetic Disorders

Some genetic disorders affect how the body processes certain compounds, which can lead to unusual urine odors. These conditions are rare, but the odors can be strong, distinctive, and persistent despite normal hygiene or dietary changes.

One example is trimethylaminuria, a rare inherited condition in which the body cannot properly break down trimethylamine. This compound forms in the gut when foods such as eggs, fish, or legumes are digested. When it builds up, it can cause a strong fish-like odor in urine, sweat, or breath. Odor intensity can vary based on diet and stress.

Another inherited condition is maple syrup urine disease, in which the body cannot process certain protein components. This can cause urine to develop a sweet, maple-like smell. The condition usually begins early in life and requires medical care.

13. Prostatitis

Prostatitis occurs when the prostate gland becomes inflamed. The prostate sits just below the bladder and helps produce fluid that forms part of semen. Inflammation can interfere with urination and may affect urine odor.

There are two main types: acute and chronic. Acute prostatitis develops suddenly and often causes more intense symptoms, while chronic prostatitis may last for months and can flare on and off. Early medical care can help reduce the risk of ongoing discomfort.

Urine may smell stronger or unpleasant, especially when bacteria are involved. Other common symptoms include burning or pain during urination, difficulty starting the stream, frequent urination, and pain in the lower abdomen, groin, or lower back. Diagnosis usually involves a physical exam and urine testing. PSA levels may rise temporarily with prostatitis, even though PSA testing is mainly used for prostate cancer screening.

14. Gastrointestinal Fistula (GIF)

A gastrointestinal fistula develops when an abnormal opening forms between digestive organs, such as between the intestines and the skin or another internal organ. This allows intestinal fluids to leak into areas where they do not belong and can disrupt how the body manages waste and nutrients.

It often occurs after abdominal surgery, injury, or intestinal diseases such as Crohn’s disease. Other possible causes include infections, blockages, radiation exposure to the abdomen, and, in rare cases, ingestion of toxic substances. A common sign is fluid leaking from the skin, often near a surgical scar or abdominal wound.

The leaking fluid may have a strong or unpleasant odor. Dehydration or infection linked to the fistula can also influence urine odor. If bacteria or toxins enter the bloodstream or urinary tract, foul-smelling urine may develop.