Increase Your Levothyroxine Dose by 12.5-25 mcg
For a patient with elevated TSH while on levothyroxine 100 mcg daily, increase the dose by 12.5-25 mcg and recheck TSH in 6-8 weeks. 1, 2
Immediate Action Required
Your current levothyroxine dose is insufficient, as evidenced by the elevated TSH. The degree of TSH elevation determines the urgency and magnitude of dose adjustment:
- If TSH is >10 mIU/L: Increase by 25 mcg immediately, regardless of symptoms, as this level carries approximately 5% annual risk of progression to overt hypothyroidism 1
- If TSH is 4.5-10 mIU/L: Increase by 12.5-25 mcg, with larger increments (25 mcg) appropriate for younger patients without cardiac disease 1, 2
- If you are >70 years old or have cardiac disease: Use the smaller 12.5 mcg increment to avoid cardiac complications 1, 2
Why This Matters for Your Health
Leaving TSH elevated—even mildly—carries significant risks:
- Increased mortality: Recent robust evidence from two large population studies shows that hypothyroid patients with TSH outside the normal range (0.5-4.5 mIU/L) have increased risk of death 2, 3
- Cardiovascular dysfunction: Untreated or undertreated hypothyroidism causes delayed cardiac relaxation, abnormal cardiac output, and adverse lipid profiles 1, 2
- Quality of life: Persistent hypothyroid symptoms including fatigue, weight gain, cold intolerance, and cognitive impairment will continue without adequate replacement 1
Monitoring Protocol After Dose Increase
- Recheck TSH and free T4 in exactly 6-8 weeks after the dose change—this represents the time needed to reach steady state given levothyroxine's 6-7 day half-life 1, 2, 4
- Target TSH range: 0.5-4.5 mIU/L with normal free T4 levels 1, 2
- Once stable: Monitor TSH annually or sooner if symptoms change 1, 2
Critical Pitfall to Avoid
Do not adjust the dose again before 6-8 weeks have passed, as levothyroxine takes this long to reach steady state 1, 2. Adjusting too frequently leads to inappropriate dosing and potential overtreatment.
Special Considerations
If You Have Cardiac Disease
Start with the conservative 12.5 mcg increment and monitor closely for angina, palpitations, or worsening heart failure 1, 2. Even therapeutic doses can unmask cardiac ischemia in patients with underlying coronary disease 1.
If You Are Pregnant or Planning Pregnancy
More aggressive normalization is warranted, targeting TSH <2.5 mIU/L in the first trimester, as subclinical hypothyroidism is associated with preeclampsia, low birth weight, and neurodevelopmental effects in offspring 1.
If You Have Thyroid Cancer
Your target TSH may be intentionally lower (0.1-0.5 mIU/L or even <0.1 mIU/L depending on risk stratification)—consult with your endocrinologist before adjusting 1, 2.
Why Not Larger Dose Increases?
Excessive dose increases risk iatrogenic hyperthyroidism, which occurs in 14-21% of treated patients and increases risk for atrial fibrillation (3-5 fold), osteoporosis, fractures, and cardiovascular mortality 1, 5, 6. Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, creating serious complications 1.
Medication Timing Reminder
Continue taking levothyroxine on an empty stomach, 30-60 minutes before breakfast, and at least 4 hours apart from iron, calcium supplements, or antacids, which reduce absorption 1, 4.