does giving blood hurt?

Story: one of my co-workers at the dance studio volunteered his time to do a charity event, a latin dance event and the cause is to give blood (there is a major blood shortage in melbourne). He had a minor accident and can't take part and asked if i'd go for him. problem is, all the dancers will be donating blood.

I'm scared. I'm terrified of needles. I'm sure some people here have donated blood sometime... please tell me does it hurt?