2. Take vitamins and other health products 1 h apart from levothyroxine tablets; 3. Take foods or medications containing iron or calcium 2 h apart; 4. Take dairy or soy foods 4 h apart. 5. Take cholestyramine or lipid-lowering resin 12 h apart from levothyroxine tablets. 6. If levothyroxine tablets are missed, take double the dose until all missed doses are made up. dose. 7. Patients should preferably take blood before taking medication on the test day, or take blood 6 hours after taking medication to avoid interference with the results. 8. Soy flour, cottonseed flour, pecans, and dietary fiber may bind to levothyroxine tablets in the gastrointestinal tract and reduce their absorption.