Can missing a week of levothyroxine cause a child to go into a hypothyroid coma?

Coma. The amount of time that levothyroxine (synthroid) takes to be eliminated from the body is relatively long in comparison to other medications, occurring over many days. It is unlikely that a patient would go into coma from low thyroid hormone levels within 7 days of stopping the medication. Still, before stopping thyroid medication, you should discuss with the child's treating physician.
No. The 1/2 life of thyroxine is 6 1/2 days - so the child may be less active and have other nonspecific complaints. Myxedema coma occurs after months of severe hypothyroidism.