Diabetes mellitus is a widespread disorder and hypoglycaemia is one of the most serious complications. The outcome might be influenced by several factors, such as the sex, previous fasting or the time of day when the episode occurs (see e.g. Somogyi effect). Our aim was to reveal these influencing factors using an insulin-induced hypoglycaemia model in Wistar rats.Fast-acting insulin (Novorapid, NR, 20NE/100g/0.2ml saline) or saline were injected intraperitoneally at the beginning of the light or dark phase (9am or 9pm) with or without 12h fasting. 60 minutes after intervention we collected trunk blood for blood glucose (BG) and to assess stress levels by measureing the corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels.NR treatment reduced BG levels and induced ACTH and CORT elevation during both periods, sexes and fasting states. However, fasting lowered the BG and elevated the ACTH levels without influencing the CORT. Fasting enhanced the effect of insulin leading to lower BG and higher ACTH and CORT levels as well. In females both the ACTH and CORT levels were higher than in males, but their BG levels did not differ significantly. Additionally, both sex and cycle influenced the effectiveness of the treatment on ACTH, but not on CORT or BG levels.Without fasting insulin injection was not really stressful despite a drop in the BG levels. Thus, for further studies fasting seems to be imperative, but the cycle of the day or the sex should not be taken into account that much.