Why Does My Urine Smell? 13 Common Causes and When to Worry

If you’ve noticed that your urine smells different than usual, you aren’t alone. While it can be unsettling, the scent, color, and frequency of your urination are often vital indicators of your overall health. From simple dehydration to underlying medical conditions, your urine provides clues about your hydration status, renal function, cardiac health, and hormonal balance.

In many cases, a change in odor is benign. However, when accompanied by other symptoms, it can signal a need for medical intervention. To help you navigate these changes, we’ve consulted experts including Tanaka Dune, M.D., a board-certified urogynecologist. Michael Ingber, M.D., a urogynecologist with the Center for Specialized Women’s Health at Garden State Urology; and Michael O’Leary, M.D., a senior urologic surgeon at Brigham and Women’s Hospital and professor of surgery at Harvard Medical School.

Common Lifestyle and Dietary Causes of Smelly Urine

Many odors are temporary and linked directly to what you consume or how much fluid you drink. These are typically not cause for concern.

• Dehydration: This is one of the most frequent causes of strong-smelling urine. When you don’t drink enough water, your urine becomes concentrated. This leads to a stronger ammonia-like smell because the waste products filtered by your kidneys aren’t sufficiently diluted. This is typically accompanied by a darker urine color.
• Coffee Consumption: Coffee acts as a mild diuretic, encouraging the body to release water. This can lead to dehydration and a subsequent ammonia scent. The metabolites produced as your body breaks down coffee can influence the smell.
• Garlic and Onions: Certain foods produce specific metabolites during digestion. Garlic and onions are common culprits that can noticeably alter the scent of your urine.
• Asparagus: Some people experience a scent often described as “rotting cabbage” after eating asparagus. This happens if you lack the enzyme necessary to break down certain compounds in the vegetable. According to research published in the British Medical Journal, roughly 40 percent of people notice this change. Those who can break down these compounds are known as asparagus anosmic.
• Vitamin Supplements: High doses of vitamins, particularly vitamin B6, can change both the odor and the color of your urine, often turning it a neon yellow-green.

Medical Conditions That Affect Urine Odor

When an odor is persistent or paired with physical discomfort, it may indicate an infection or a metabolic issue.

Urinary Tract and Vaginal Infections

Urinary tract infections (UTIs) and bladder infections are common causes of foul-smelling urine. Because women have shorter urethras, they are more susceptible to these infections. According to the National Institute of Diabetes and Digestive and Kidney Diseases, between 40 to 60 percent of women will experience at least one UTI in their lifetime, and 1 in 4 will have multiple.

While yeast infections don’t directly change the composition of urine, they can create a foul smell when infection-related bacteria in the vagina come into contact with urine during urination. Women may sometimes mistake unusual vaginal odor for smelly urine.

Sexually Transmitted Infections (STIs)

Certain STIs, such as chlamydia and trichomoniasis, can cause smelly discharge and painful urination in both men and women, according to the CDC. Because these infections can be asymptomatic but still impact the reproductive system, regular screening is essential.

Diabetes and Metabolic Disorders

A sweet-smelling scent can be an early indicator of diabetes or prediabetes. In both type 1 and type 2 diabetes, the body’s inability to process sugar leads to glucose leaking into the urine. The term “mellitus” actually means sweet-tasting. If you have already been diagnosed with diabetes, sweet-smelling urine may indicate that your blood sugar is not currently under control.

Rare metabolic disorders can also be the cause:

• Maple Syrup Urine Disease: A deficiency in enzymes needed to break down amino acids, resulting in sweet-smelling urine. This is typically diagnosed in infancy.
• Phenylketonuria (PKU): A genetic defect that prevents the breakdown of the amino acid phenylalanine, which can cause musty-smelling breath and urine.

Other Potential Health Concerns

Less common but more serious conditions can also manifest as changes in urine odor.

• Kidney Stones: These form when chemicals in the urine crystallize. According to the National Kidney Foundation, larger stones can cause cloudy, foul-smelling, or even bloody urine, often accompanied by significant pain.
• Bladder Fistulas: These are abnormal openings between the bladder and another organ, such as the bowel or vagina. According to the Urology Care Foundation, these can be caused by inflammatory bowel diseases (like Crohn’s disease or ulcerative colitis), certain cancers, or recent surgeries. This can result in urine that smells like stool or contains gas.
• Medication Side Effects: Certain drugs can alter the pH of your urine or change the metabolites your body produces. This includes some diabetes medications and Methenamine, a drug used to treat chronic UTIs.

Summary of Urine Odors and Potential Causes

When to See a Doctor

If a change in urine odor is the only symptom you are experiencing, it is often benign. However, you should schedule an appointment with a healthcare provider if the odor is persistent or accompanied by any of the following “red flags”:

• Visual Changes: Cloudy or bloody urine.
• Physical Pain: Burning during urination or pain in the lower abdomen or lower back.
• Frequency Changes: Urinating significantly more or less often than usual, or experiencing sudden urinary urgency.
• General Illness: Fever or general malaise.

Most doctors recommend a visit if these symptoms persist for a few days. A simple urine test can often quickly identify the presence of glucose, bacteria, or blood, allowing for a timely and effective treatment plan.