Those are definitely factors. It's also good to up your fluid intake, preferably with something high in sugar.

（ once everything is set and ready, she sits down beside him and pushes a juicebox into his hand. hope you like peach juice! ）

Drink this first, candy afterwards. It helps.

（ technically, it can be given on either side of the donation, but she prefers before so that the digestive enzymes are already breaking down the sugar by the time the donation is concluded. ）