I have hypothyroidism and take levothyroxine 150 µg daily; my recent TSH is 0.05 mIU/L—how should I adjust my medication?

Reduce Your Levothyroxine Dose Immediately

Your TSH of 0.050 mIU/L indicates you are overtreated with levothyroxine, and you should decrease your dose by 25 mcg (from 150 mcg to 125 mcg daily) to prevent serious cardiovascular and bone complications. 1, 2

Why This Matters

Your current TSH is severely suppressed below the normal range (0.45-4.5 mIU/L), creating a state of iatrogenic (medication-induced) subclinical hyperthyroidism. 1, 2 This is not a trivial finding—prolonged TSH suppression at this level significantly increases your risk of:

• Atrial fibrillation and cardiac arrhythmias (3-5 fold increased risk, especially if you're over 60 years old) 1, 2
• Osteoporosis and fractures (particularly hip and spine fractures if you're postmenopausal or over 65) 1, 2
• Increased cardiovascular mortality 1, 2
• Accelerated bone mineral density loss 1, 2

Approximately 25% of patients on levothyroxine are unintentionally maintained on doses high enough to fully suppress TSH, and this overtreatment carries substantial morbidity risks. 1

Specific Dose Adjustment

Decrease your levothyroxine from 150 mcg to 125 mcg daily (a 25 mcg reduction). 1, 2 This represents approximately a 17% dose reduction, which is appropriate for your degree of TSH suppression. 2

• For TSH <0.1 mIU/L (which yours is), the recommended reduction is 25-50 mcg 1, 2
• Since your TSH is 0.050 mIU/L (just at the 0.1 threshold), starting with a 25 mcg reduction is reasonable 2
• If you have cardiac disease, are elderly, or have other risk factors, this conservative 25 mcg reduction is especially appropriate 1, 2

Monitoring Plan

Recheck your TSH and free T4 in 6-8 weeks after making this dose change. 1, 3 This interval is critical because levothyroxine requires 4-6 weeks to reach steady state in your body. 1, 3

• Your target TSH should be 0.5-4.5 mIU/L (the normal reference range) 1, 2
• Once your TSH normalizes, continue monitoring every 6-12 months or sooner if symptoms develop 1
• Do not adjust your dose again before the 6-8 week mark, as premature adjustments can lead to overcorrection 1

Important Exceptions

This recommendation assumes you do NOT have thyroid cancer or thyroid nodules requiring intentional TSH suppression. 1, 2 If you have a history of thyroid cancer, consult your endocrinologist before making any dose changes, as your target TSH may be intentionally lower based on your cancer risk stratification. 1, 2

• Low-risk thyroid cancer patients with excellent response: target TSH 0.5-2.0 mIU/L 1
• Intermediate-to-high risk patients: target TSH 0.1-0.5 mIU/L 1
• Structural incomplete response: target TSH <0.1 mIU/L 1

Critical Pitfalls to Avoid

• Do not ignore this suppressed TSH—even if you feel fine, the cardiovascular and bone risks are real and accumulate over time 1, 2
• Do not reduce your dose too aggressively (more than 25-50 mcg at once), as this may cause hypothyroid symptoms to emerge 2
• Do not recheck your TSH before 6-8 weeks, as earlier testing will not reflect the true steady-state effect of your dose change 1, 3
• Do not assume your symptoms are unrelated to overtreatment—fatigue, palpitations, tremor, heat intolerance, or weight loss may all indicate excessive thyroid hormone 1

Additional Considerations

If you are over 60 years old, postmenopausal, or have cardiac disease, your risk from this TSH suppression is even higher, and you should prioritize normalizing your TSH quickly. 1, 2 Consider obtaining an ECG to screen for atrial fibrillation if you have cardiac risk factors. 1

Ensure adequate calcium (1200 mg/day) and vitamin D (1000 units/day) intake to protect your bones while your TSH is being corrected. 1