Normal Glucose Tolerance with Preserved Beta Cell Function
This patient does not have diabetes and shows no evidence of autoimmune type 1 diabetes. The combination of normal blood glucose (85 mg/dL), preserved C-peptide (2.1 ng/mL), and negative autoantibodies (GAD <5.0, IA2 <5.4) indicates normal pancreatic beta cell function without autoimmune destruction. 1
Interpretation of Laboratory Results
C-peptide Analysis:
- The C-peptide level of 2.1 ng/mL (approximately 700 pmol/L) is well above the threshold for insulin deficiency 1
- C-peptide values >600 pmol/L strongly suggest type 2 diabetes phenotype if diabetes were present, but more importantly, rule out type 1 diabetes and indicate robust endogenous insulin production 1, 2
- This level confirms the pancreas is producing adequate amounts of insulin and reflects preserved pancreatic beta cell function 1
Autoantibody Status:
- GAD <5.0 and IA2 <5.4 are both negative, excluding autoimmune-mediated beta cell destruction 3
- The absence of these autoimmune markers predicts stable beta cell function and rules out immune-mediated type 1 diabetes 3
- GADA is the most frequent marker among type 1 diabetes patients, and its absence is highly significant 3
Glucose Status:
- Blood glucose of 85 mg/dL is completely normal (diabetes requires fasting glucose ≥126 mg/dL or random glucose ≥200 mg/dL) 4
- This normal glucose with preserved C-peptide indicates no current glucose metabolism disorder 1
Clinical Diagnosis
This patient has:
- Normal glucose tolerance
- Preserved pancreatic beta cell function
- No evidence of autoimmune diabetes
- No indication for diabetes treatment 1, 5
Management Recommendations
No diabetes-specific intervention is required. 1
Appropriate follow-up includes:
- Standard preventive care and lifestyle counseling for diabetes prevention if risk factors are present (obesity, family history, sedentary lifestyle) 4
- No need for repeat C-peptide or autoantibody testing unless clinical symptoms of hyperglycemia develop 1, 5
- Routine screening for diabetes per standard guidelines based on age and risk factors 4
Important Clinical Caveats
Do not misinterpret these results as pre-diabetes or early diabetes:
- C-peptide values <200 pmol/L (<0.6 ng/mL) would be required to suggest type 1 diabetes 1
- Fasting glucose 100-125 mg/dL or HbA1c 5.7-6.4% would be required for pre-diabetes diagnosis 4
- This patient meets neither criterion 4, 1
If symptoms of hypoglycemia were present (which is not indicated in this case), the normal glucose with elevated C-peptide would warrant evaluation for insulinoma, but the blood glucose of 85 mg/dL excludes this concern 4