sign, symptom, or diagnosis, it is appropriate to assign both the V code and the code describing the reason for the non-routine test. 18
The difference is in the types of non -nutritive sweeteners used. Diet Coke has aspartame while Coke Zero has a mix of aspartame and acesulfame potassium. The beverages have different levels of sweetness and off tastes (I.e. high levels of aspartame have a metallic taste) as a result.
It is marketed as having a taste that is indistinguishable from standard Coca-Cola, as opposed to Diet Coke which has a different flavor profile. In the United Kingdom and Japan, Coca-Cola Zero is being renamed to Coca-Cola Zero Sugar and is being reformulated to taste more like standard Coca-Cola.