Screening lab denials/angry patients

We have an issue (as I am sure most do) where the patient presents for a physical and has what they deem as "screening labs", however the patient hasa diagnosis. Example: Patient wants screening cholesterol but is already on medication. The ICD-9 code is diagnostic, pateints insurance company says "they need to code it as screening" patient is in the middle and angry.

I am looking to see what others do for these situations.

Thank you

Screening lab denials/angry patients