What could be the cause of urine smelling like ammonia?

Urea is related: Urea is related to ammonia. Urea is the byproduct of our protein metabolism, and is disposed of in our urine. If urine is concentrated (due to not drinking enough fluids), it can have an ammonia odor. Other things can affect people's sense of smell, such as nasal changes, hormonal changes, pregnancy, etc... Warm urine should have a stronger odor than cold urine, too.