Cystic endometrial hyperplasia--pyometra complex (CEH-P) is a well recognized condition, usually affecting old bitches during diestrus. Live-threatening CEH-P occurs consequently to septic/inflammatory state. Many authors have showed that inflammatory environments course with marked increase in cytokine levels such as IL-1, IL-6, IL-18 and TNF-α. This cytokines usually lead to insulin resistance due to indirect stimulation stress hormone production and directly by decrease insulin intracellular signaling. Fourteen bitches in diestrus and twelve bitches with pyometra were submitted to blood samples collection after overnight starvation for glucose (portable glucometer) and insulin measures (radioimmunoassay). Use of any kind of contraceptive was considered exclusion rule. Four insulin sensitivity indexes were calculated: insulinogenic index (II = insulin μU/mL / glycemia mg/dL); amended insulin: glucose ratio (AI:GR = insulin μU/mL x100 / glycemia-30); HOMAR (HR = insulin μU/mL x glycemia mmol/L / 22.5) and HOMA B(HB = 20 x insulin μU/mL / glycemia mmol/L-3.5). Comparisons between means was performed by t-test for all variants except HOMA indexes that were expressed as medians with relatives 25/75 quartiles and compared by Mann-Whitney test. Although glucose mean do not differ between groups (anestrus 86.7 ± 11 mg/dL vs. CEH-P 84.9 ± 12 mg/dL; p > 0,05), insulin values were significantly higher (p < 0.05) in CEH-P group (43.5 ± 21.8 μU/mL) than in group anestrus (21 ± 9.2 μU/mL). All insulin indexes were significantly higher (p < 0.05) for CEH-P group [II = 0.504 ± 0.24; AI:GR = 78,6 ± 36; HR = 2.65 (1.2/3.7) and HB = 4.1 (1.5/4.7)] compared with diestrus group [II = 0.25 ± 0.12; AI:GR = 39.1 ± 19.4; HR = 1,18 (0.75/1.4) and HB = 1.3 (0.8/2.05)]. It was possible to conclude that CEH-P represents an insulin resistance state in bitches, and glycemia alone is not trusty for this evaluation. It's interesting that mean II and AI:GR are above reference values (II < 0.235 and AI:GR < 30) for dogs in both groups, making evident the insulin resistance status in diestrus also. Higher HR values from CEH-P group agree with data provided by II and AI:GR. However higher HB values indicates increased secretory activity from beta cells. Thus CEH-P may represent a risk factor for beta cell exhaustion.