I'm going to a party next monday but have a fasting blood test at 9:50 am the next day. Can I still go to the party and drink alcohol?

You may have to... ...deal with the consequences (insurance, work, recommendation for further testing, medical uncertainty) if your next-day lab results prove abnormal. It's your decision whether to take that chance and enjoy alcohol at your party, or reduce the risk and enjoy a non-alcoholic beverage instead.