I'm not sure! Straight up blood donation takes away some stuff that takes a while to regenerate, so you're not allowed to donate more often than once every 8 weeks. By contrast, you can donate plasma twice a week in the US (although if I remember correctly, other countries limit you to once every two weeks).

In other words, what they take out of you during blood donations is a lot more...precious.

I'm O- though so I don't know if they'll let me donate plasma (they want my blood!). I was thinking of alternating plasma and blood in order to get a little bit of both if I can.

You can donate plasma twice a week, as opposed to every other month for blood.