PKU, short for phenylketonuria, is another inherited disorder where the body can't break down phenylalanine, an amino acid found in protein. "If PKU is untreated, or if foods containing phenylalanine are eaten, the breath, skin, ear wax, and urine may have a 'mousy or 'musty' odor," Dr. Ellerkmann says. This unpleasant smell is from the buildup of phenylalanine in the body, and if untreated, could lead to serious health complications such as intellectual disability, seizures, and brain damage. But don't let this freak you out too much -- PKU is usually diagnosed in infancy, so if you haven't developed it yet, you're probably good.
You're taking medication with sulfa
Sulfa is found in some diabetes medication, antibiotics, migraine medicine, anti-inflammatories, and (quite fittingly) diuretics. Although the correlation isn't strong or that widely understood, Dr. Ellerkmann says taking a medication that contains sulfa might make your pee smell funky. If anything, it's something to be aware of if you notice a change in pee smell with no other explanation.