Introduction. Enteroendocrine K cells secrete the incretin hormone glucose-dependent insulinotropic peptide (GIP) and are predominately located in the duodenum. Theoretically, GIP levels should decrease after gastric bypass surgery due to the duodenal exclusion of K cell stimulation. However, studies have found conflicting data regarding the changes in intestinal GIP secretion after gastric bypass. We utilized lymphatic sampling as a more sensitive medium than plasma to measure gastrointestinal GIP concentrations in rodents. We hypothesized that a marginal change in GIP concentration after duodenal-jejunal exclusion (DJE) is due to a compensatory increase in GIP production and secretion from distal small bowel enteroendocrine cells. Methodology. We performed a DJE (n=10), which bypasses the duodenum and first 10 cm of the jejunum with a 15 cm jejunal limb, or sham surgery (n=9) in 12 week-old, male, Wistar rats. An oral glucose tolerance test (OGTT) was performed at approximately 10 days after surgery. Superior mesenteric lymphatic cannulation was performed 2 weeks after DJE or sham surgery. An intragastric mixed meal was administered and lymph and plasma samples were collected for one hour and analyzed for total GIP concentration. 4 intestinal segments were obtained for GIP quantification: (1) duodenum (2) 10 cm distal to the ligament of Treitz (LOT) (distal to the duodenojejunostomy in DJE rats), (3) 25 cm distal to the LOT (distal to the roux-en-y anastamosis in DJE rats) and (4) ileum. Results. There was no difference in body weight at any time point between the surgical groups. There was no difference in glucose concentration area under the curve (AUC). DJE rats tended to have an increased insulin concentration AUC compared to sham rats (insulin conc AUC mean ± SE, 214 (ng/ml)min ± 19 vs 180 (ng/ml)min ± 13 respectively, p=0.18). There was no difference in plasma or lymphatic GIP concentration AUC between DJE and sham rats (lymph: 15240 (pg/ml)min ± 2651 vs 16939 (pg/ml)min ± 3588 respectively, p=0.70). GIP intestinal content (% GIP/total protein) was increased in the mid-jejunum (distal to the roux-en-y anastamosis) in DJE rats compared to sham rats (4.11% ± 0.37 vs 2.52% ± 0.30 respectively, p=0.01). Conclusions. Plasma and lymphatic GIP concentrations did not significantly change after DJE in Wistar rats. Bypassing duodenal K cells after duodenal exclusion is countered by an increase in mid-jejunal GIP intestinal content and secretion at the new site of primary nutrient absorption. This increase in intestinal GIP content likely explains the marginal and conflicting changes in plasma GIP concentrations after gastric bypass.