Thyroid Function

I got a call from the pediatrician's office today about Ruby's bloodwork.Her levels on her thyroid test were 3.5 which they told me was borderline for low function.I will have to take Ruby back in 6 weeks for another thyroid test.Do any of you have experience with this?I didn't know all the right questions to ask when I was on the phone with the dr.'s office and now I feel a little worried.They did tell me if they need to she will be treated with medication.