Levothyroxine Dosage Calculator
Full Replacement Dosing
Calculate levothyroxine dose for full thyroid replacement based on body weight
kg
TSH-Based Dose Adjustment
Estimate dose adjustment based on current TSH level
mcg
mIU/L
Formula
Full Replacement: 1.6 mcg/kg/day | Post-thyroidectomy: 1.7 mcg/kg/day | TSH Suppression: 2.0-2.5 mcg/kg/day | Elderly/cardiac: Start 25 mcg, titrate by 12.5-25 mcg every 4-6 weeks
Frequently Asked Questions
How is levothyroxine dose calculated?
Full thyroid replacement is typically dosed at 1.6 mcg/kg/day of ideal body weight. For TSH suppression in thyroid cancer, higher doses of 2.0-2.5 mcg/kg/day may be needed. Elderly patients and those with cardiac disease start at lower doses (25-50 mcg) with gradual titration.
How should I take levothyroxine?
Take on an empty stomach, 30-60 minutes before breakfast (or at bedtime, 3+ hours after eating). Separate from calcium, iron, antacids, and other medications by at least 4 hours. Take consistently at the same time daily.
How often should TSH be checked?
TSH should be rechecked 6-8 weeks after starting or changing the dose. Once stable, check TSH every 6-12 months. More frequent monitoring during pregnancy, after significant weight changes, or when starting interacting medications.
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