Levothyroxine Supply for 8-Week Interval
Order a 60-day (8-week) supply of levothyroxine 25 mcg, which equals 56 tablets.
Calculating the Supply Duration
- Levothyroxine is taken once daily, so for an 8-week monitoring interval you need 56 tablets (7 days × 8 weeks = 56 days) 1
- Most pharmacies dispense in 30-day increments, so you should order two 30-day supplies (60 tablets total) to cover the full 8-week period until TSH recheck 1
- The standard monitoring interval after initiating or adjusting levothyroxine is 6-8 weeks, which allows sufficient time to reach steady-state thyroid hormone levels 1
Rationale for 8-Week Monitoring Interval
- After starting levothyroxine or adjusting the dose, TSH and free T4 should be rechecked in 6-8 weeks because this represents the time required for levothyroxine to reach steady-state concentrations in the body 1
- Checking TSH earlier than 6 weeks risks making dose adjustments before steady state is achieved, which can lead to inappropriate dosing 1
- Once TSH is stabilized within the target range (0.5-4.5 mIU/L), subsequent monitoring can be extended to every 6-12 months 1
Practical Prescribing Considerations
- Write the prescription for "levothyroxine 25 mcg, take 1 tablet by mouth once daily, dispense 60 tablets" to ensure adequate supply through the recheck appointment 1
- Instruct the patient to take levothyroxine on an empty stomach, 30-60 minutes before breakfast, and at least 4 hours apart from calcium, iron supplements, or antacids to optimize absorption 1
- For elderly patients (>70 years) or those with cardiac disease, the 25 mcg starting dose is appropriate and should be titrated gradually by 12.5-25 mcg increments every 6-8 weeks based on TSH response 1
Common Pitfall to Avoid
- Never recheck TSH before 6 weeks after initiating or adjusting levothyroxine, as premature testing will show artificially abnormal values that do not reflect steady-state thyroid function and may prompt unnecessary dose changes 1