One concern about feeding dry food to cats is that its high carbohydrate. Starch content could result in high blood glucose levels which could have long term negative health effects. This study investigated low, medium and high starch diets on postprandial blood glucose and insulin levels in adult dogs and cats. Results showed that only the high starch diet produced significant postprandial plasma glucose concentrations in dogs and cats. In dogs this significant increase only occurred 7 hours post prandially whereas in cats the significant elevation lasted from 11 to 19 hours after the meal. This lag may be due to evolutionary adaptations in cats resulting in slower digestive and absorptive ability for complex carbohydrate in felines. Plasma insulin was significantly elevated in dogs 4-8 hours after eating the medium starch meal and 2-8 hours after the high starch diet. In cats, plasma insulin was significantly greater than baseline from 3-7 and 11-17 hours after the high starch diet only.