Previous studies in small mammals showed that blood-sucking bugs (Reduviidae, Heteroptera) can be used to obtain blood from veins difficult to access by human experimenters. In the present study, we validated the use of reduviid bugs for endocrinological studies in endotherms using domestic rabbits as a model organism. Two processes could alter the hormone concentrations in the blood ingested by the bug: (1) Mixing of ingested blood with saliva, gut fluid, or hemolymph and (2) digestive processes. We compared concentrations of progesterone, testosterone, and hydrocortisone in blood samples that were acquired from domestic rabbits (Oryctolagus cuniculus) by bugs (Dipetalogaster maxima) with hormone concentrations in blood obtained from the same individual rabbits with a conventional method, i.e., syringe. We found no significant differences in hormone concentrations between the two methods. Thus, the mixing effect is negligible immediately after the blood meal. In addition, we also could not find significant changes in concentrations of progesterone and hydrocortisone for up to 8h after the blood meal. Whereas levels of hydrocortisone remained unchanged for even 24h, progesterone levels significantly increased between eight and 24h. Thus, the bugs' excretory apparatus did not fractionate between water and hormones. Thirdly, we hypothesized that reduviid bugs impose less stress on the rabbits than the conventional method. We showed that deviations in hydrocortisone concentrations between the two blood sampling routines were lower when the bug method was used first and higher when the conventional method was used first. Thus, bugs imposed less stress on the study animals than the conventional method. Overall, we conclude that reduviid bugs present a minimally invasive method for obtaining blood from endotherm animals for endocrinological studies.