Management of C-Peptide 0.1 ng/mL (Severe Insulin Deficiency)
A C-peptide level of 0.1 ng/mL (approximately 33 pmol/L) indicates severe insulin deficiency consistent with type 1 diabetes and requires immediate initiation of intensive insulin therapy for survival. 1, 2
Diagnostic Confirmation
This C-peptide value (<80 pmol/L or <0.24 ng/mL) is diagnostic of absolute insulin deficiency and does not require repeat testing. 1, 2
Check islet autoantibodies (GAD, IA-2, ZnT8) to confirm autoimmune type 1 diabetes, though 5-10% of type 1 diabetes patients are antibody-negative. 1, 2
Do not delay insulin initiation while awaiting antibody results—the C-peptide level alone confirms absolute insulin requirement. 2
Immediate Treatment Algorithm
Initiate basal-bolus insulin therapy immediately:
Start rapid-acting insulin analog (such as insulin lispro) before each meal at approximately 0.3-0.5 units/kg/day divided among meals. 3
Add basal insulin (such as insulin detemir or NPH) once or twice daily, starting at 0.3-0.5 units/kg/day. 3, 4
Total daily insulin typically ranges 0.5-1.0 units/kg/day, adjusted based on glucose monitoring. 3
Critical Monitoring Requirements
Implement intensive glucose monitoring with finger-stick testing before meals, at bedtime, and when symptomatic. 2
Target HbA1c <7.0% to reduce microvascular complications, though individualize based on hypoglycemia risk. 5
Monitor HbA1c every 3 months and adjust insulin doses accordingly. 5
Educate patient on recognition and self-treatment of hypoglycemia, as this is the most common adverse effect of insulin therapy. 4
Long-Term Management Considerations
Consider insulin pump therapy (continuous subcutaneous insulin infusion) for optimal glycemic control, particularly if multiple daily injections fail to achieve targets or if severe hypoglycemia occurs. 3
With C-peptide this low, the patient has no meaningful endogenous insulin production and will require lifelong insulin therapy. 2, 6
Monitor for diabetic ketoacidosis risk, as patients with absolute insulin deficiency are at high risk during illness, stress, or insulin omission. 3
Important Clinical Caveats
Never discontinue insulin in this patient—doing so will result in diabetic ketoacidosis. 2
This level of C-peptide (<80 pmol/L) confirms the patient will not respond to oral antidiabetic agents or non-insulin therapies. 2, 6
Insulin requirements may change with intercurrent illness, stress, changes in physical activity, or meal patterns—adjust doses accordingly. 4
Rotate injection sites continuously within given areas to prevent lipodystrophy and ensure consistent insulin absorption. 4
Beta-blockers may mask hypoglycemia symptoms—use with caution and counsel patients accordingly. 4