I am not an expert, but here is what the Decision Memo says:
"CMS has determined that fasting C-peptide levels will only be considered valid when a concurrently obtained fasting glucose is ≤ 225 mg/dL. Insulinopenia is defined as a fasting C-peptide level that is less than or equal to 110 percent of the lower limit of normal of the laboratory’s measurement method. Alternatively, for patients with renal insufficiency and a creatinine clearance (actual or calculated from age, gender, weight and serum creatinine) ≤ 50 ml/minute, insulinopenia is defined as a fasting C-peptide level that is less than or equal to 200 percent of the lower limit of normal of the laboratory’s measurement method. Levels only need to be documented once in the medical records."
So whether or not a 1.1 ng/dl qualifies really depends on you lab reference range. My lab (Quest) has a reference range of 1-3 ng/dl, so 1.1 ng/dl may just barely qualify. That being said, it also says that you only need to document it once in the medical records, so you previous test result may also be accepted. Perhaps others will chime in.