Levothyroxine: timing and interactions
Levothyroxine (Synthroid, Levoxyl) replaces thyroid hormone, and it's sensitive to timing and other substances. Small habits make a big difference in how well it works.
How to take it
- Usually on an empty stomach, 30–60 minutes before breakfast (or at bedtime, well after eating).
- Take it consistently the same way each day.
- Swallow with water — separate from coffee by 30–60 minutes.
What to separate it from
These can block absorption if taken at the same time — separate by about 4 hours:
- Calcium (supplements or antacids).
- Iron supplements.
- Some other minerals and certain acid reducers.
Other interactions
Some medicines change your thyroid dose needs. Tell your prescriber about any new medicine, and don't switch between brand and generic without letting your doctor know — thyroid levels are checked to keep the dose right.
Consistency is everything: Same time, same way, every day. If you change how you take it, mention it — your levels may need rechecking.
Check your own medicines free
See how your prescriptions, supplements, and food may interact — organized by the part of the body they affect.
Open the medication tool →Important: This article is educational and not medical advice. It does not replace your pharmacist or prescriber. Always confirm decisions about your medicines with a qualified professional, and call your local emergency number for emergencies. In the U.S., Poison Control is 1-800-222-1222.