Does anyone know if it's possible that Levothyroxine causes joint pain. I was diagnosed with an under active thyroid 2 years ago and put on 50mg Levothyroxine. Within a couple of weeks I started getting joint pain. My doctor referred me to a rheumatologist and they say that I have inflammatory arthritis and prescribed anti inflammatory drugs. I am convinced it's the Levothyroxine that's causing it but none of the doctors agree that this drug causes these side effects. Many thanks.