What's Making Your Urine Smell?

What's Making Your Urine Smell?

The average person produces six and a half cups of urine a day. Although urine is comprised of a vast assortment of metabolic breakdown products (mostly waste and extra fluid filtered out of the blood by the kidneys), it normally has a surprisingly inoffensive smell. If you are properly hydrated and healthy, there should be little or even no odor. If you notice an odd or unpleasant smell, a range of factors could be at play. Find out what causes smelly urine, and whether it merits a trip to your doctor.

Urinary Tract Infection

When bacteria sneak into the bladder via the urethra, they may cause a urinary tract infection (UTI). These infections are more common in women than in men because women’s urethras are much shorter than men’s, making it easier for bacteria to get to the bladder where they can start to multiply. In fact, about half of all women will develop a UTI at least once in their lives. One of the most common UTI symptoms is burning or pain with urination; many people also notice that their urine appears cloudy or even bloody, with a strong, unpleasant odor.


If you’ve ever noticed that your urine smells a little off after eating asparagus, you’re in good company; about 40 percent of people have the gene needed to create this response. The scent comes from a compound called asparagusic acid. Once asparagusic acid gets into your system, enzymes in the body break it down into sulfur-containing compounds, invoking that characteristic rotten-egg smell. Fortunately, the smell dissipates and leaves after a few rounds of urination. (Interestingly, some people are unable to smell this compound.)


If you're not consuming adequate water, your urine will become overly concentrated and can start to develop stronger-than-normal odor. This is likely due to the now-concentrated amounts of urea and other chemicals. Consider it a friendly warning that you should increase your fluid intake.

Uncontrolled diabetes

In unmanaged diabetes, the body is unable to process glucose (sugar) for energy due to insufficient insulin, so it begins breaking down fat for energy instead. This creates toxic byproducts called ketone bodies, which can be detected via a fruity smell on the person's breath and in his or her urine.

Maple Syrup Urine Disease

This rare genetic disorder means you have trouble metabolizing specific amino acids, which are the building blocks of protein. Because these amino acids are not broken down, they, along with any byproducts, accumulate in the fluids and cells of the body. Besides leaving individuals feeling tired and irritable, the condition has a telltale symptom: the development of a maple syrup-like odor to the urine, sweat, and earwax.

Sexually transmitted infection

Typically, the smell of one’s urine will not change as the result of a sexually transmitted infection (STI). That said, certain STIs do cause an unpleasant vaginal odor, which you might notice when you urinate. Trichomoniasis, for example, is a common STI caused by a parasite; some patients will notice a strong or fishy-smelling vaginal odor.

What to do

If you notice the smell of your urine simply seems more potent than normal, try increasing your fluid intake. You’ll know you’re drinking enough when your urine is pale yellow to clear in color. If you are experiencing other urinary symptoms, such as burning or urge to urinate frequently, see your health care provider; you may have a UTI. Most uncomplicated UTIs will be cured with a short course of antibiotics. Maple Syrup Urine Disease is very rare and is typically noticed and diagnosed soon after birth, so if you have it, chances are you already know about it.

A note for people with diabetes...

If you have diabetes but your condition is well monitored and under control, you shouldn’t notice anything off about the smell of your urine. If, however, you detect a sweet odor after urination, accompanied by a sudden increase in both thirst and urination frequency, check in with your physician and explain your symptoms.