Cats aged 2-6 years and weighing at least 4.5 kg, as well as dogs aged 2-7 years and weighing at least 25 kg, are eligible to donate blood. The animal must be up-to-date on vaccinations, undergo a pre-procedure examination and should not have chronic diseases. The blood type and Rh factor for compatibility check between the donor and recipient is determined using a simple test. No special preparation is required for donation. The most important factors are the willingness to lend a paw, ensuring that the animal abstains from food on the day of donation and not worrying (the last is especially crucial for the owner).