Increase Levothyroxine Dose by 25 mcg
For a patient with TSH 22 mU/L on levothyroxine 150 mcg, increase the dose by 25 mcg to 175 mcg daily. This TSH level indicates significant undertreatment requiring prompt dose adjustment 1, 2.
Rationale for Dose Increase
TSH >10 mU/L warrants dose adjustment regardless of symptoms, as this degree of elevation carries approximately 5% annual risk of progression to overt hypothyroidism and is associated with adverse effects on cardiovascular function, lipid metabolism, and quality of life 1, 2.
The recommended increment is 25 mcg for most patients under 70 years without cardiac disease 1, 2. This provides adequate correction while avoiding overtreatment.
If the patient is over 70 years or has cardiac disease, use a smaller 12.5 mcg increment to minimize risk of cardiac complications 1, 2.
Monitoring Protocol
Recheck TSH and free T4 in 6-8 weeks after dose adjustment to evaluate response 1, 2.
Target TSH should be within the reference range (0.5-4.5 mU/L) with normal free T4 levels 1, 2.
For patients with cardiac disease or atrial fibrillation, consider repeating testing within 2 weeks rather than waiting the full 6-8 weeks 1.
Critical Pitfalls to Avoid
Do not make excessive dose increases (>25 mcg in standard patients), as this can lead to iatrogenic hyperthyroidism with increased risk for atrial fibrillation, osteoporosis, and cardiac complications 1, 3.
Wait the full 6-8 weeks between dose adjustments before making further changes, as levothyroxine has a long half-life and TSH takes time to reach steady state 1, 3.
Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, highlighting the importance of careful monitoring after adjustment 1.
Assess for Adherence Issues
Before increasing the dose, verify medication adherence and proper administration 1:
Levothyroxine should be taken on an empty stomach, ideally 30-60 minutes before breakfast 3.
Iron, calcium supplements, and certain medications reduce levothyroxine absorption and should be separated by at least 4 hours 3.
Enzyme inducers (phenytoin, carbamazepine, rifampin) can reduce levothyroxine efficacy 3.