Resuming Levothyroxine After One Week Off
Yes, you can resume your same dose of levothyroxine after being off for one week. 1
Rationale for Resuming the Same Dose
- Levothyroxine has a long half-life of approximately 7 days, meaning that after one week off, significant drug levels remain in your system 2
- The occasional missing of tablets causes no harm due to this extended half-life, and the same principle applies to a one-week interruption 2
- Your thyroid status will not have changed significantly enough in one week to warrant a different dose 3
What to Expect After Resumption
- TSH levels may be slightly elevated when checked 4-6 weeks after resuming therapy, but this does not necessarily indicate the need for dose adjustment 1
- A new equilibrium is reached approximately 6 weeks after any change in levothyroxine dosing or interruption 2
- Do not check TSH levels earlier than 6-8 weeks after resuming your medication, as earlier testing will not reflect steady-state levels and may lead to inappropriate dose changes 1, 4
Monitoring Recommendations
- Resume your previous dose immediately without any adjustment 1
- Schedule TSH and free T4 testing 6-8 weeks after resuming therapy to confirm adequate replacement 1, 4
- If TSH is >10 mIU/L at that time, a dose increase of 12.5-25 mcg may be warranted 4
- If TSH remains within the reference range (0.5-4.5 mIU/L), continue your current dose and recheck annually 1
Important Caveats
- If you are pregnant or planning pregnancy, contact your physician immediately, as levothyroxine requirements increase during pregnancy and any interruption requires closer monitoring 1, 4
- For patients with cardiac disease or over 70 years of age, notify your physician before resuming, as more cautious monitoring may be appropriate 1
- If you develop symptoms of hypothyroidism (fatigue, cold intolerance, weight gain) or hyperthyroidism (palpitations, tremor, heat intolerance) after resuming, contact your physician rather than waiting for scheduled testing 1
Critical Pitfall to Avoid
- Do not reduce your dose when resuming therapy - the one-week interruption does not create a need for lower dosing, and undertreatment carries risks including persistent hypothyroid symptoms and adverse cardiovascular effects 1