My ketones are a little high doc says to reduce carb intake & drink water only that's all i drink & i don't eat many carbs at all what's causing this?

Often happens: I'm assuming you feel well and are not diabetic. If you miss a meal, you may be burning fat somewhat inefficiently. Actually, the less carbs you eat, the more likely you are to produce a few extra ketones -- this is the basis for one of the dubious fad diets. Mild ketonuria shouldn't be overinterpreted. Treat the person, not the labs.