You cannot bring a full year's supply of your thyroid medication at one time, and you will need to establish care with a US doctor to get local refills. The FDA allows a {"term": "foreign-national", "text": "foreign national"} to bring or ship only a 90-day supply of prescription medication. Because Texas requires a US-licensed prescriber, a local pharmacy cannot fill your Canadian prescription.

The rules for importing your medication

The FDA strictly limits personal importation of prescription drugs. You cannot bring a full year's worth of medication. The rule allows foreign nationals to bring or ship a maximum of a 90-day supply at a time.

If you are staying in the US longer than 90 days as a temporary foreign national, you can have additional 90-day supplies sent to you by mail or courier. If you choose this route, the FDA suggests including documentation in the package to prove it is for your personal use. This includes a copy of your visa or passport, a letter from your doctor, and a copy of your prescription in English.

The exemption that allows you to have unapproved foreign medication shipped to you by mail applies because you are a foreign national. If you are moving to the US as a permanent resident (a Green Card holder) rather than on a temporary visa, you do not qualify for this specific foreign national exemption.