The effect of sacubitril/valsartan on urinary C-peptide excretion and endogenous insulin secretory capacity in a patient with type 2 diabetes: a case report

In this case, 24-h urinary C-peptide excretion was abnormally elevated despite preserved endogenous insulin secretory capacity, as assessed by the glucagon stimulation test. Although this observation is based on a single case and cannot be generalized, it suggests that sacubitril/valsartan may interfere with the interpretation of urinary C-peptide levels. Therefore, in such clinical contexts, dynamic tests such as the glucagon stimulation test may serve as a useful adjunct to avoid potential overestimation of insulin secretory capacity when relying solely on urinary C-peptide levels.