What is ketosis?

Answer 1

The accumulation in the body of the ketone bodies: acetone, beta-hydroxybutyric acid, and acetoacetic acid (Taber's Medical Dictionary, 18th ed.). This condition results from incomplete metabolism of fatty acids and is common found in poorly controlled Diabetes. It may also be caused by starvation, pregnancy, and high fat diets. Excess ketone bodies are excreted in the urine causing a condition known as ketonuria. In the olden days before glucometers, the amount of ketone bodies found in urine (identified by dipsticking random urine sample) determined the amount of insulin the patient required.
One of the functions your liver performs is to converts fat into fatty acids and ketones to be used by the body for energy. Ketones are molecules produced by the liver during fat metabolism and are a normal source of fuel and energy for the body. When your body is in the state of ketosis, it is using fat as its' primary source of energy. This state can be induced by significantly reducing carbohydrate intake and forcing your body to use it's reserved energy stores. This method of reducing fat in the body is known as the low carb or keytosis diet.
a diet that contains insufficient carbohydrate

Answer 2

Most likely it is slang for the drug , Ketamine. Which is used in hospitals to mildy put people under, yet still conscious. It is closely related to PCP.