What are the reference ranges for a mixed meal tolerance test at 1 and 2 hours for glucose, C-peptide, insulin, and proinsulin levels?

From the Research

The reference ranges for a mixed meal tolerance test (MMTT) are generally considered to be: glucose <140 mg/dL at 1 hour and <120 mg/dL at 2 hours post-meal, C-peptide 1.1-4.4 ng/mL at baseline, increasing to 3.0-9.0 ng/mL at 1 hour and 2.5-8.0 ng/mL at 2 hours, insulin 5-15 μIU/mL fasting, rising to 30-230 μIU/mL at 1 hour and 15-170 μIU/mL at 2 hours, and proinsulin 2-20 pmol/L fasting, increasing to 10-60 pmol/L at 1 hour and 5-50 pmol/L at 2 hours, as supported by the most recent study 1.

Key Findings

• The MMTT is a valuable tool for assessing pancreatic beta cell function and insulin secretion capacity, as it uses physiological stimulation with carbohydrates, proteins, and fats to trigger insulin release 2.
• The test is particularly useful for diagnosing persistent post-bariatric hypoglycemia, with a sensitivity of 88.9% in patients who have undergone surgery more than three years ago 2.
• The reproducibility of glucose and insulin responses to MMTTs varies by subtraction of fasting values, glucose status, and time, with insulin secretion and action explaining ~20% of MMTT responses 1.

Reference Ranges

• Glucose: <140 mg/dL at 1 hour and <120 mg/dL at 2 hours post-meal
• C-peptide: 1.1-4.4 ng/mL at baseline, increasing to 3.0-9.0 ng/mL at 1 hour and 2.5-8.0 ng/mL at 2 hours
• Insulin: 5-15 μIU/mL fasting, rising to 30-230 μIU/mL at 1 hour and 15-170 μIU/mL at 2 hours
• Proinsulin: 2-20 pmol/L fasting, increasing to 10-60 pmol/L at 1 hour and 5-50 pmol/L at 2 hours

Clinical Implications

• Values outside these ranges may indicate various metabolic disorders, including diabetes, insulin resistance, or insulinoma, depending on the pattern observed 3.
• The MMTT can be used to monitor the effectiveness of treatments for these disorders and to adjust treatment plans as needed 4.