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Estimates levothyroxine dose for thyroid hormone replacement, accounting for patient age and cardiac risk factors.
Dose = 1.6 * weight
1.0–2.0 µg/kg/day
Interpret results together with the patient's clinical presentation.
Specialty
EndocrinologyCategory
EndocrinologyDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-06
Formula
Normal Range
1.0–2.0 µg/kg/day
| Classification | Range |
|---|---|
Conservative starting dose | <1.1 |
Moderate dose | 1–1.6 |
Full replacement dose | ≥1.6 |
Estimates a weight-based levothyroxine dose (≈1.6 µg/kg/day) using the calculator's implemented equation, illustrating the weight-based reference point used when starting levothyroxine replacement.
The calculator reports the weight-based estimate (1.6 µg/kg/day) as the 'full replacement dose.' The calculator's only input is body weight — age, cardiac risk, and pregnancy are not inputs and are not reflected in the number. Actual starting doses are individualized; many patients, especially older adults or those with cardiac disease, are started at much lower doses (commonly 25–50 µg/day) and titrated using TSH.
A weight-based estimate (≈1.6 µg/kg/day) provides a reference point for full levothyroxine replacement, but real-world starting doses are individualized — particularly in older adults and patients with cardiac disease — and are titrated to a target TSH.
A 70 kg adult is being evaluated for thyroid hormone replacement.
Inputs:
Estimated dose = 1.6 × 70 = 112 µg/day — reported as the full replacement dose estimate.
Both use the same 1.6 µg/kg/day formula. Thyroid Dose provides the estimate, while Levothyroxine Dose includes clinical guidance on titration, cardiac precautions, and pregnancy adjustments.
In healthy patients, dose can be titrated every 6–8 weeks. In elderly or cardiac patients, increase more slowly (every 6–12 weeks).
Yes. Take 30–60 minutes before breakfast with water only. Separate from calcium, iron supplements, and PPIs.
Disclaimer: This calculator is intended for educational and clinical decision support. The result is not a prescription: actual starting doses are individualized, current treatment guidance and patient factors must be considered, and this calculator does not apply any automatic adjustment for age, cardiac disease, or pregnancy.
Clinical dosing with titration guidance.
Requires clinical context.