Dual 5α-reductase inhibitor (type 1 and type 2)
Dutasteride with thyroid medication (levothyroxine)
Levothyroxine is one of the most prescribed medications worldwide, and many adults on it also use chronic medications such as Dutasteride (Dutasteride). 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 0.5mg.
How Dutasteride affects thyroid medication
Levothyroxine absorption is sensitive to timing relative to food, calcium, iron and several medications. Whether Dutasteride interferes depends on Dutasteride — most agents in Dual 5α-reductase inhibitor (type 1 and type 2) have no clinically meaningful effect on thyroid hormone levels, but a small number affect TSH or T4 free fraction. Dutasteride irreversibly inhibits both isoenzymes of 5α-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT).
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. Dutasteride at 0.5mg can usually be taken at any time relative to the levothyroxine dose, but the prescribing information for Dutasteride should be checked for specific timing instructions.
Frequently asked questions
Will Dutasteride affect my thyroid levels? ▾
Most Dual 5α-reductase inhibitor (type 1 and type 2) medications do not directly affect thyroid hormone levels at 0.5mg. 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 Dutasteride relative to levothyroxine? ▾
Levothyroxine is taken on an empty stomach with at least a 30-minute fast and 4-hour separation from interacting medications. Dutasteride at 0.5mg usually has no specific timing constraint relative to levothyroxine; the pharmacist confirms based on the prescribing information for Dutasteride.
Products containing Dutasteride
More on Dutasteride
- With alcoholDutasteride and alcohol — is it safe to drink?
- With foodShould Dutasteride be taken with food?
- Side effectsDutasteride side effects: common, rare and warning signs
- Dosage guideDutasteride dosage guide: how much to take and when
- OnsetHow fast does Dutasteride start working?
- DurationHow long does Dutasteride last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.