How long can you go without thyroid medication?

The half-life (time taken for amount of drug in your body to be reduced by half) of levothyroxine is 6 - 7 days in euthyroid, 9 - 10 days in hypothyroid and 3 - 4 days in hyperthyroid. So, it would take few weeks for your body to get rid of the thyroid medication. But you may start to experience symptoms within first week of not taking medication. Moreover, once you restart the medication it will take 3 - 5 days for it to start the action and almost few weeks to reach maximum effect. In all this time, you need to suffer from the symptoms. Hence, it's safer to take medications regularly and monitor thyroid levels.