Background: A modified 13 C-mixed triglyceride breath test ( 13 C -MTGT) detects moderate pancreatic exocrine insufficiency noninvasively and reliably, but it requires prolonged breath sampling (6 hours (hr)). Objective: We aimed to investigate whether 13 C -MTGT can be abbreviated, to optimize clinical usability. Methods: We analyzed the 13 C-MTGT of 200 consecutive patients, retrospectively. Cumulative 1-5 hr 13 C-exhalation values were compared with the standard parameter (6-hr cumulative 13 C-exhalation). We determined the sensitivity and specificity of shortened breath sampling periods, by comparison with the normal values from 10 healthy volunteers, whom also underwent a secretin test to quantitate pancreatic secretion. Moreover, we evaluated the influence of gastric emptying (GE), using a 13 C-octanoic acid breath test in a subset (N ¼ 117). Results: The 1-5 hr cumulative 13 C-exhalation tests correlated highly and significantly with the standard parameter (p < 0.0001). Sensitivity for detection of impaired lipolysis was high (!77%), but the specificity was low (!38%) for the early measurements. Both parameters were high after 4 hrs (88% and 94%, respectively) and 5 hrs (98% and 91%, respectively). Multivariate linear correlation analysis confirmed that GE strongly influenced early postprandial 13 C-exhalation during the 13 C-MTGT. Conclusion: Shortening of the 13 C -MTGT from 6 to 4 hrs of duration was associated with similar diagnostic accuracy, yet increased clinical usability. The influence of GE on early postprandial results of the 13 C-MTGT precluded further abbreviation of the test.