From the FDA Drug Label
The recommended starting daily dosage of levothyroxine sodium tablets in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1 For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms. Full replacement dose is 1.6 mcg/kg/day. Some patients require a lower starting dose. Titrate dosage by 12.5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid. The recommended starting daily dosage of levothyroxine sodium tablets in pediatric patients with primary, secondary, or tertiary hypothyroidism is based on body weight and changes with age as described in Table 2 Titrate the dosage (every 2 weeks) as needed based on serum TSH or free-T4 until the patient is euthyroid
The appropriate dose of Levothyroxine (Euthyrox) is:
- 1.6 mcg/kg/day for adults with primary, secondary, or tertiary hypothyroidism, with some patients requiring a lower starting dose.
- Lower starting dose for patients at risk of atrial fibrillation or with underlying cardiac disease, and for geriatric patients.
- Titration by 12.5 to 25 mcg increments every 4 to 6 weeks for adults, and every 2 weeks for pediatric patients, based on serum TSH or free-T4 until the patient is euthyroid.
- Pediatric dosing is based on body weight and age, as described in Table 2, with starting daily dosages per kg body weight ranging from 10 to 15 mcg/kg/day for 0 to 3 months, to 1.6 mcg/kg/day for greater than 12 years with growth and puberty complete. 1
From the Research
The appropriate dose of Levothyroxine (Euthyrox) is highly individualized, but the typical starting dose for adults with hypothyroidism is 25-50 mcg daily, with a maintenance dose between 100-200 mcg daily, as supported by the most recent and highest quality study 2.
Key Considerations
- The dose of Levothyroxine should be adjusted based on serum TSH levels, with the goal of achieving a normal TSH level between 1-2 mU/L 3.
- Elderly patients or those with heart disease should start at lower doses (12.5-25 mcg daily) and gradually increase as needed 3, 2.
- Levothyroxine should be taken on an empty stomach, 30-60 minutes before breakfast, with a full glass of water, and at the same time each day for consistent absorption.
Monitoring and Adjustments
- Regular blood tests (TSH, T4) are necessary to monitor thyroid function and adjust dosing accordingly 2, 4.
- Dose adjustments may be needed during pregnancy, with significant weight changes, or when starting certain medications that interact with Levothyroxine 2.
- It is essential to avoid under-replacement and over-replacement, as both can cause health problems, and never adjust the Euthyrox dose without medical supervision 3, 2.
Individualized Dosing
- The optimal daily Levothyroxine dose can be predicted based on pretreatment thyroid hormone indexes, with serum TSH concentration being the best index 5.
- However, the most recent and highest quality study 2 provides a more straightforward approach to dosing, emphasizing the importance of individualization and regular monitoring.