My thyroid test recently came back as 14 meaning that I need to be put on tablets, thyroid runs in my family so I've been tested for years I've always had abnormal levels but never got to the number where I needed to take tablets until recently. I've been on them for about 3 weeks now. For the past week I've been feeling sick, tired, weak and so on. I was wondering if it was my thyroid doing this? I thought because I'm now on tablets it wouldn't be like this? I had symptoms before it was confirmed that I had an underactive thyroid but they weren't this bad. Could it be that I need a higher dosage of tablets? I don't know, I'm only 17 so I'm not sure on all of this stuff.