Though donations of blood are unpaid, blood plasma can earn you 400 CZK. In order to donate your plasma you must be between 18 and 65, weigh above 55 kg, have a medical examination, have valid EU medical insurance and have a “good knowledge” of Czech. Certain medical conditions such as diabetes, autoimmune disorders and hemophilia, to name a few, preclude a person from donating plasma. If you fit the criteria, you can donate once every 14 days. Visit here and here for more detailed information on plasma donation.