What is the next step in adjusting my levothyroxine dose, currently at 66 micrograms (mcg)?

Levothyroxine Dose Adjustment from 66 mcg

Increase your levothyroxine dose by 12.5 to 25 mcg daily, bringing your total dose to either 75 mcg or 88 mcg, depending on your age and cardiac status. 1, 2

Determining Your Specific Dose Increase

If you are under 70 years old without cardiac disease:

• Increase by 25 mcg to a total of 88 mcg daily (or round to 100 mcg if 88 mcg is unavailable) 1, 2
• This more aggressive titration is appropriate for younger patients without heart conditions 1

If you are over 70 years old OR have cardiac disease (coronary artery disease, atrial fibrillation, heart failure):

• Increase by 12.5 mcg to a total of 75 mcg daily 1, 2
• Smaller increments minimize risk of cardiac complications including angina, arrhythmias, or cardiac decompensation 1, 3

Monitoring After Dose Adjustment

Recheck TSH and free T4 in 6-8 weeks after making this dose change 1, 2, 4

• This 6-8 week interval is critical because levothyroxine requires this time to reach steady state in your system 1
• Do not adjust your dose more frequently than every 6-8 weeks, as this is a common pitfall that leads to overtreatment 1

If you have atrial fibrillation, serious cardiac disease, or multiple medical conditions:

• Consider rechecking within 2 weeks instead of waiting the full 6-8 weeks 1
• More frequent monitoring prevents cardiac complications in high-risk patients 1

Target TSH Range

Your goal TSH should be 0.5-4.5 mIU/L with normal free T4 1, 2

• This represents the reference range for adequate thyroid hormone replacement 1
• Both TSH and free T4 should be measured together, as free T4 helps interpret ongoing abnormal TSH levels 1

Critical Pitfalls to Avoid

Do not increase your dose by more than 25 mcg at a time 1

• Larger dose jumps risk iatrogenic hyperthyroidism, which increases your risk for atrial fibrillation, osteoporosis, fractures, and cardiac complications 1, 3
• Approximately 25% of patients on levothyroxine are unintentionally maintained on excessive doses that fully suppress TSH 1

Do not adjust your dose before 6-8 weeks have passed 1

• Adjusting too frequently before reaching steady state is a common error that leads to dose instability 1

Take levothyroxine consistently on an empty stomach 5, 6

• Take 30-60 minutes before breakfast or at bedtime (at least 4 hours after your last meal) 6
• Inconsistent timing or taking with food impairs absorption and makes dose optimization impossible 6, 7

Long-Term Monitoring

Once your TSH stabilizes in the target range:

• Recheck TSH every 6-12 months 1, 2
• Recheck sooner if you develop new symptoms, change weight significantly, become pregnant, or start medications that interact with levothyroxine 1, 6