remind your doctor that smoking, muscular exertion (muscles produce ammonia when active and absorb it when resting), exercise before having the
blood test
and leaving the tourniquet on too long when taking the
blood, CAN CAUSE HIGH AMMONIA READINGS.
And please tell him that wanting to treat somebody based on ONE ammonia reading is absolutely ridiculous and he should be ashamed of himself.
Source:
http://www.labtestsonline.org/understanding/analytes/ammonia/test.