For domestic flights within the U.S. or EU, the TSA and other agencies do not strictly require over-the-counter (OTC) pills to be in their original containers. You are generally allowed to use pill organizers for convenience. However, for international travel, the rules are much more rigid. In 2026, many countries (like Japan or those in the Middle East) have very strict drug laws; having loose, unidentified pills can lead to long delays at customs or even confiscation. It is highly recommended to keep all pills in their original packaging or at least have a photo of the label on your phone. If you are carrying large quantities of vitamins or supplements, keeping them sealed in their original bottles prevents any suspicion of "commercial intent" or illegal substances, ensuring a much smoother transition through international border checkpoints.