From the FDA Drug Label
Administer levothyroxine sodium tablets as a single daily dose, on an empty stomach, one-half to one hour before breakfast with a full glass of water to avoid choking or gagging Administer levothyroxine sodium tablets at least 4 hours before or after drugs known to interfere with levothyroxine sodium absorption
Levothyroxine (Synthroid) Administration:
- The medication should be taken on an empty stomach, one-half to one hour before breakfast.
- It should be taken at least 4 hours before or after drugs known to interfere with levothyroxine sodium absorption.
- There is no information that suggests it can be taken at any time of day, only that it should be taken as a single daily dose, on an empty stomach, one-half to one hour before breakfast 1 1.
From the Research
Levothyroxine (Synthroid) is best taken at bedtime, as it has been shown to improve thyroid hormone concentrations and lower TSH concentrations compared to morning administration, as demonstrated in a study published in 2007 2.
Importance of Consistency
While the timing of levothyroxine administration can impact its effectiveness, consistency is also crucial for optimal results. Taking Synthroid at the same time daily helps maintain steady thyroid hormone levels in your bloodstream.
Factors Affecting Absorption
Food, certain medications, and supplements can interfere with levothyroxine absorption, which is why taking it on an empty stomach is recommended. If morning administration is difficult, taking it consistently at another time is better than varying the timing day to day.
Potential Interactions
It is essential to maintain a 4-hour separation from calcium, iron supplements, antacids, and certain other medications that can bind to levothyroxine and reduce its absorption. Proton pump inhibitors, such as pantoprazole, can also affect thyroid function tests, but the timing of their administration (morning or evening) does not seem to have a significant impact, as shown in a 2023 study 3.
Gastric Malabsorptive Disorders
In patients with gastric malabsorptive disorders, the absorption of levothyroxine may be impaired, and alternative formulations, such as softgel capsules or liquid solutions, may be necessary, as discussed in a 2020 article 4.
Monitoring and Adjustments
If you need to change your dosing schedule, consult your healthcare provider first, as they may recommend thyroid function testing after the change to ensure your levels remain appropriate. A study published in 2015 5 highlighted the importance of monitoring thyroid hormone levels when changing the administration time of levothyroxine.
Key Considerations
In summary, taking levothyroxine at bedtime, maintaining consistency, avoiding potential interactions, and monitoring thyroid hormone levels are essential for optimal treatment outcomes.