Reduce Levothyroxine Dose Immediately
Your current levothyroxine dose of 125 mcg is excessive, as evidenced by the suppressed TSH of 0.18 mIU/L, and should be reduced by 12.5–25 mcg to prevent serious cardiovascular and bone complications. 1
Why Your Current Dose Is Too High
Your TSH of 0.18 mIU/L falls well below the normal reference range of 0.45–4.5 mIU/L, indicating iatrogenic (medication-induced) subclinical hyperthyroidism 1. This represents overtreatment with levothyroxine, which approximately 25% of patients on thyroid hormone replacement inadvertently experience 1.
Immediate Dose Adjustment Required
Reduce your levothyroxine dose by 12.5–25 mcg immediately (from 125 mcg to either 112.5 mcg or 100 mcg) 1. The specific reduction depends on:
- Smaller reduction (12.5 mcg): If you are over 70 years old or have any cardiac disease 1
- Larger reduction (25 mcg): If you are younger and have no cardiac risk factors 1
After dose adjustment, recheck TSH and free T4 in 6–8 weeks to evaluate response, targeting a TSH within the reference range of 0.5–4.5 mIU/L 1.
Serious Risks of Continued TSH Suppression
Cardiovascular Complications
Prolonged TSH suppression at your current level significantly increases cardiovascular risks:
- Atrial fibrillation risk increases 3–5 fold, particularly dangerous if you are over 60 years old 1
- Cardiovascular mortality increases up to 3-fold in individuals over 60 with TSH below 0.5 mIU/L 1
- Cardiac dysfunction including increased heart rate, abnormal cardiac output, and ventricular hypertrophy 1
Bone Health Consequences
TSH suppression accelerates bone loss:
- Significant bone mineral density decline, especially in postmenopausal women 1
- Increased risk of hip and spine fractures in women over 65 years with TSH ≤0.1 mIU/L, though your TSH of 0.18 carries lower but still elevated risk 1
Special Considerations
If You Have Thyroid Cancer
Do not adjust your dose without consulting your endocrinologist first 1. Some thyroid cancer patients require intentional TSH suppression:
- Low-risk 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
However, if you were prescribed levothyroxine for primary hypothyroidism (not thyroid cancer), dose reduction is mandatory 1.
If You Have Cardiac Disease or Are Elderly
More frequent monitoring may be warranted—consider repeating testing within 2 weeks of dose adjustment rather than waiting 6–8 weeks 1. Obtain an ECG to screen for atrial fibrillation if you are over 60 years or have cardiac disease 1.
Long-Term Monitoring
Once your TSH normalizes to the target range of 0.5–4.5 mIU/L:
- Repeat TSH testing every 6–12 months 1
- Recheck sooner if symptoms change 1
- Ensure adequate calcium (1200 mg/day) and vitamin D (1000 units/day) intake to protect bone health, especially if TSH has been chronically suppressed 1
Common Pitfall to Avoid
Never ignore a suppressed TSH while on levothyroxine—even if you feel well, silent cardiovascular and skeletal damage can occur 1. A large population study found no correlation between low TSH and hyperthyroid symptoms in patients not taking levothyroxine, meaning you may feel fine while incurring serious harm 1.