When should I stop taking levothyroxine (T4) or adjust my dose?

When to Stop or Taper Levothyroxine

Direct Answer

You should consider stopping levothyroxine if you were started on treatment for subclinical hypothyroidism (TSH 4.5-10 mIU/L) without clear indication, or if your thyroid function has normalized spontaneously—but you must never taper the dose; instead, discontinue completely and monitor closely with repeat testing in 6-8 weeks. 1, 2

Key Principle: No Tapering Required

• Levothyroxine does not require tapering when discontinuing because it has a long half-life and the body will gradually clear it over several weeks 2
• The FDA label does not recommend or require dose tapering for discontinuation 3
• Simply stop the medication completely and monitor thyroid function tests 6-8 weeks later 1, 2

When Discontinuation Should Be Considered

Patients Started for Subclinical Hypothyroidism (TSH 4.5-10 mIU/L)

• 30-60% of elevated TSH levels normalize spontaneously on repeat testing, indicating many patients may have been started on unnecessary lifelong treatment 4, 1
• A recent 2025 pilot RCT demonstrated that discontinuing levothyroxine in patients with subclinical hypothyroidism was well-tolerated, with 98% completion rate and minimal adverse events 2
• Only 2 out of 24 patients (8%) in the placebo group required restarting levothyroxine over 6 months—one for TSH >10 mIU/L and one for fatigue 2

Patients with Transient Hypothyroidism

• Failure to recognize transient hypothyroidism leads to unnecessary lifelong treatment 1
• Transient causes include subacute thyroiditis, postpartum thyroiditis, medication-induced thyroid dysfunction, or recovery from nonthyroidal illness 4, 5
• If TSH was elevated during acute illness or medication changes, recheck 3-6 months after resolution before committing to lifelong therapy 4

Patients with Low TSH on Therapy (Overtreatment)

• Development of low TSH (<0.5 mIU/L) on therapy suggests overtreatment or recovery of thyroid function; dose should be reduced or discontinued with close follow-up 1
• For TSH <0.1 mIU/L without thyroid cancer indication, discontinuation should be strongly considered to avoid complications including atrial fibrillation, osteoporosis, and cardiovascular mortality 1
• Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, increasing risks 1

Specific Discontinuation Protocol

Step 1: Confirm Appropriateness for Discontinuation

• Review original indication for starting levothyroxine 1
• If started for TSH 4.5-10 mIU/L without symptoms, positive TPO antibodies, or pregnancy planning, discontinuation is reasonable 1, 2
• If currently overtreated (TSH <0.5 mIU/L) without thyroid cancer, discontinuation should be considered 1
• Exclude patients who require continued therapy: TSH persistently >10 mIU/L, overt hypothyroidism (low free T4), thyroid cancer requiring TSH suppression, or pregnancy 1, 3

Step 2: Stop Medication Completely (No Tapering)

• Discontinue levothyroxine entirely—do not taper the dose 2
• Inform patient that symptoms may develop gradually over 4-8 weeks as medication clears 2
• Educate patient about hypothyroid symptoms to monitor: fatigue, cold intolerance, weight gain, constipation 6

Step 3: Monitor After Discontinuation

• Recheck TSH and free T4 at 6-8 weeks after discontinuation 1, 2
• If TSH remains <10 mIU/L and patient is asymptomatic, continue monitoring every 3-6 months 1
• If TSH rises to >10 mIU/L or patient develops significant symptoms, restart levothyroxine 1, 2

Critical Situations Where You Should NOT Stop

Never Discontinue in These Patients:

• Overt hypothyroidism (elevated TSH with low free T4) 1, 6
• TSH persistently >10 mIU/L on repeat testing, which carries 5% annual risk of progression to overt hypothyroidism 1
• Pregnant women or those planning pregnancy, as subclinical hypothyroidism is associated with preeclampsia, low birth weight, and neurodevelopmental effects 1
• Thyroid cancer patients requiring TSH suppression for disease control 1, 3
• Positive TPO antibodies with TSH >7 mIU/L, indicating 4.3% annual progression risk to overt hypothyroidism 1

Common Pitfalls to Avoid

• Do not taper levothyroxine—the long half-life makes tapering unnecessary and only delays assessment of true thyroid status 2
• Do not rely on a single TSH value before discontinuing; confirm stability with repeat testing 4, 1
• Do not discontinue without arranging follow-up testing at 6-8 weeks, as some patients will require restarting 2
• Do not assume all patients need lifelong therapy once started—the 2025 RCT showed 92% of patients with subclinical hypothyroidism tolerated discontinuation well 2
• Do not confuse patients requiring TSH suppression for thyroid cancer with those treated for primary hypothyroidism—management differs fundamentally 1

Evidence Quality Considerations

• The 2025 pilot RCT provides the highest quality recent evidence that levothyroxine discontinuation is feasible and safe in selected patients with subclinical hypothyroidism 2
• Multiple guidelines acknowledge that 30-60% of elevated TSH levels normalize without treatment, supporting a trial of discontinuation in appropriate patients 4, 1
• The lack of benefit from levothyroxine in subclinical hypothyroidism (TSH <10 mIU/L) in multiple RCTs supports considering discontinuation in this population 4, 6