What is the standard levothyroxine replacement dose?

The full replacement dose for primary hypothyroidism in otherwise healthy adults is 1.6 mcg/kg/day. For subclinical hypothyroidism, lower doses (25-75 mcg/day) are often sufficient. Doses are adjusted based on TSH monitoring at 6-8 weeks.

Why is levothyroxine started at lower doses in elderly patients?

Elderly patients and those with cardiac disease (especially coronary artery disease) are started at 12.5-25 mcg/day to avoid precipitating angina, arrhythmia, or heart failure. Thyroid hormone increases cardiac demand and oxygen consumption.

How should levothyroxine be taken?

Levothyroxine should be taken on an empty stomach 30-60 minutes before breakfast or at bedtime (2-3 hours after last meal). It should be taken consistently. Absorption is reduced by calcium, iron, fiber, proton pump inhibitors, and cholestyramine.

Levothyroxine Starting Dose

Calculate levothyroxine replacement dose: healthy adult hypothyroidism 1.6 mcg/kg/day; elderly or cardiac disease start 12.5-25 mcg/day; post-thyroidectomy may need 2.0 mcg/kg/day.

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Levothyroxine Starting Dose

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Frequently Asked Questions

What is the standard levothyroxine replacement dose?

Why is levothyroxine started at lower doses in elderly patients?

How should levothyroxine be taken?