As the other posters have said, eating a low-carb diet will show ketones. Everyone produces ketones, 24 hours a day, so their presence should not be alarming.
However, you said that you have a high amount present. On a relative scale, what is "high"? Are you doing a colormetric assay or a blood test? If you're doing a colormetric assay on a test strip, make sure that the strip has not expired and that moisture has not entered the vial, or else dipping the strip in pure fresh water will indicate high ketones in your drinking water.
People on "Atkins"-like diets will also show a moderate level of ketones. Also, if you haven't eaten in several hours, energy is found in the body's fat.
Your urine will have a "sweet smell" to it when ketones are high. Some people don't even bother with ketone tests because they can sniff out the smell, but personally, I'd suggest using the strips for a qualitive test.
