Side effects from ritalin?

My 16 year old daughter is going to a doctors appointment to be tested for ADHD. What do you think the chances are that the doctor confirms it and prescribes medicine? What are some common side effects of the medicine? i heard weight loss was a common thing and i was wondering how much weight she should expect to lose. Sorry i know this question is kind of hard to answer knowing so little about her but she basically fits all the symptom lists for adhd perfectly. Thanks for the help! I really appreciate it!