Every country has its own values, rules, and methods for blood donation (be it about anonymity, retribution, etc.), but please consider getting informed, and donate.
According to the Établissement Français du Sang (roughly translated to: French Blood Institute), the key point is to donate again, possibly on a regular basis.
Various possibilities in France: donate “full” blood (2 months delay between each, takes about 10 minutes), or selectively (plasma or platelets, 2 to 4 weeks delay between each, takes about a full hour).
You can save lives. Will you do it?
Many thanks to Helen for reminding me to write a note about important things.