Synthetic progestin (emergency contraception)
Levonorgestrel with thyroid medication (levothyroxine)
Levothyroxine is one of the most prescribed medications worldwide, and many adults on it also use chronic medications such as Levonorgestrel (Levonorgestrel). The combination is generally safe, but levothyroxine's narrow therapeutic index and finicky absorption mean a few practical points matter more than for most other co-administered drugs at 1.5mg.
How Levonorgestrel affects thyroid medication
Levothyroxine absorption is sensitive to timing relative to food, calcium, iron and several medications. Whether Levonorgestrel interferes depends on Levonorgestrel — most agents in Synthetic progestin (emergency contraception) have no clinically meaningful effect on thyroid hormone levels, but a small number affect TSH or T4 free fraction. In emergency contraception, levonorgestrel works primarily by delaying or inhibiting ovulation when taken before the LH surge.
Practical timing
According to standard endocrine practice, levothyroxine is taken on an empty stomach at least 30 minutes before food and 4 hours from interacting medications. Levonorgestrel at 1.5mg can usually be taken at any time relative to the levothyroxine dose, but the prescribing information for Levonorgestrel should be checked for specific timing instructions.
Frequently asked questions
Will Levonorgestrel affect my thyroid levels? ▾
Most Synthetic progestin (emergency contraception) medications do not directly affect thyroid hormone levels at 1.5mg. Some affect TSH testing, hormone-binding proteins or T4 free fraction in subtle ways. Routine thyroid function tests every few months catch any meaningful drift.
When should I take Levonorgestrel relative to levothyroxine? ▾
Levothyroxine is taken on an empty stomach with at least a 30-minute fast and 4-hour separation from interacting medications. Levonorgestrel at 1.5mg usually has no specific timing constraint relative to levothyroxine; the pharmacist confirms based on the prescribing information for Levonorgestrel.
Products containing Levonorgestrel
More on Levonorgestrel
- With alcoholLevonorgestrel and alcohol — is it safe to drink?
- With foodShould Levonorgestrel be taken with food?
- Side effectsLevonorgestrel side effects: common, rare and warning signs
- Dosage guideLevonorgestrel dosage guide: how much to take and when
- OnsetHow fast does Levonorgestrel start working?
- DurationHow long does Levonorgestrel last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.