Most of the plasma donation centers need you to go through a pre-screening while you book your appointment.
In that pre-screening, you need to declare if you have diseases or not, have done body modifications, or have any STDs or STIs.
After that, most centers will perform a quick blood test on the day you actually donate your plasma.
And even after you donate your plasma, that goes through another round of tests to finally become eligible for life-saving treatment.