Levothyroxine starting dose
Full replacement versus low-dose start, by age and cardiac disease.
Inputs
1 of 3years
Actual (total) body weight
Coronary disease or arrhythmia
Patient values are shared with every calculator.
When to use
- Starting levothyroxine for overt hypothyroidism.
Pearls and pitfalls
- Recheck TSH 6 to 8 weeks after starting or changing.
- Take on an empty stomach, apart from calcium, iron, and PPIs.
- Subclinical hypothyroidism often needs only 25 to 75 mcg/day.
Why use
Separates who can start at full dose from who must start low.
Full replacement ≈ 1.6 mcg/kg/day (actual weight); older adults or coronary disease: 12.5–25 mcg/day