Most changes in urine color and odor are temporary and can be attributed to certain foods, vitamins, and medicines. But sometimes smelly or discolored urine can indicate an underlying medical condition.

Many people don’t pay attention to the color or smell of their urine unless they notice a sudden change. Because urine is primarily made of water, it usually has only a slight odor and appears mildly yellow. Yellow is the most common color of urine, caused by a biochemical waste product known as urobilin, or urochrome. Urobilin is produced when your body breaks down older red blood cells. (1)

What Can Cause Smelly Urine?

Foods, medication, vitamins, and medical conditions can all cause your urine to smell.

What Do the Color and Smell of Your Urine Tell You?

The food most commonly associated with changing the smell of your urine is asparagus; eating the green stalks often results in “asparagus pee.” According to a study published in December 2016 in the journal BMJ, 40 percent of the population has a gene that allows them to smell a change in their urine after they eat asparagus. (2)

Medication, supplements, and vitamins can alter urine odor due to the artificial coatings on capsules. You’re also more likely to smell a change in your urine if you’re taking pills that contain vitamin B6. (3)

Smelly urine can also indicate that you have a medical condition that needs attention. These can include: (4)

Dehydration can cause a strong, ammonia-like odor, signaling that you need to rehydrate. If your urine smells sweet or like ammonia, it might be an early sign of a urinary tract infection (UTI). (4) A yeasty smell can indicate bacteria from a potential yeast infection. Foul-smelling urine can be a sign of a sexually transmitted disease, such as chlamydia or trichomoniasis. (5)

If your urine smells fruity and you’ve been rushing to the bathroom more frequently, you may be at risk for type 2 diabetes. (5)

Some people may have a genetic disorder that affects the scent of urine. Trimethylaminuria is a condition in which the body cannot break down trimethylamine, a chemical compound with a strong odor akin to rotting eggs that can also occur in urine. (6)

Women who are ovulating don’t experience a change in urine odor, but hormones like estrogen and progesterone can give them a super sense of smell that makes them more sensitive to the odor. (7) Once you become pregnant, pregnancy hormones can cause urine odor to change. A strong urine odor might also indicate a urinary tract infection, which pregnant women are at a higher risk for developing. (8)