U.S. doctors online nowAsk doctors free
A 40-year-old member asked:

Can it take longer for synthroid (thyroxine) to work vs. levothroid?

1 doctor answer1 doctor weighed in
Dr. Linda DiMeglio
Pediatric Endocrinology 28 years experience
No: They should work in the same time frame. However, it is always good when switching brands of l-thyroxine to recheck thyroid hormone levels about 6 weeks afterwards, to make sure you are stable on the new brand.

90,000 U.S. doctors in 147 specialties are here to answer your questions or offer you advice, prescriptions, and more. Get help now:

Ask doctors free
Educational text
Free
Talk to a doctor
24/7 visits - just $39!
50% off with $15/month membership

Similar questions

A 40-year-old member asked:

Does it take longer for Synthroid (thyroxine) to work vs. Levothyroid?

1 doctor answer1 doctor weighed in
Dr. Philip Kern
Endocrinology 43 years experience
Not really: Absorption of each thyroid preparation is a little different, and you should not switch brands, if possible. But both synthroid (thyroxine) and Levothroid are long acting hormones, with a half-life of 1 week. I doubt you would notice a difference with regards to onset of action, for example if you were starting to take them for hypothyroidism.
A 44-year-old member asked:

How long should it take Synthroid (thyroxine) to start working?

1 doctor answer1 doctor weighed in
Dr. Richard Shewbridge
Endocrinology 33 years experience
2-5 days.: Synthroid (levothyroxine) has a very long half-life. Levels start to rise in a few days, but take 5-6 weeks to reach a plateau.
A 33-year-old member asked:

How long does it take for the increase in Synthroid (thyroxine) dosage to take effect?

1 doctor answer1 doctor weighed in
Dr. Philip Kern
Endocrinology 43 years experience
Weeks: You may start to feel a difference in 1-2 weeks, but you need to give a new dosage 6 weeks before rechecking thyroid blood levels.
Lebanon
A 23-year-old female asked:

How long does it take for Synthroid (thyroxine) to leave your system after ceasing to take it?

1 doctor answer2 doctors weighed in
Dr. Karen Butler
Family Medicine 21 years experience
Long half like: Synthesis has a long half life so it will take a while to be out if the system
Dr. Michael Kleerekoper
A Verified Doctor commented
A US doctor answered Learn more
The real question is whether or not this patient is hypothyroid.
Mar 9, 2016
A female asked:

If I take Synthroid (thyroxine) first thing in the morning, how long do I have to wait before I take Propranolol?

1 doctor answer1 doctor weighed in
Dr. H Robert Silverstein
Specializes in Cardiology
I tell my patients: thy need not wait: I think other MD's make too big a deal of separating these meds. Take them & see what your lab tests show. HRS, MD,FACC www.thepmc.org

90,000 U.S. doctors in 147 specialties are here to answer your questions or offer you advice, prescriptions, and more. Get help now:

Ask doctors free
Educational text
Free
Talk to a doctor
24/7 visits - just $39!
50% off with $15/month membership
Last updated Apr 8, 2013

Disclaimer:

Content on HealthTap (including answers) should not be used for medical advice, diagnosis, or treatment, and interactions on HealthTap do not create a doctor-patient relationship. Never disregard or delay professional medical advice in person because of anything on HealthTap. Call your doctor or 911 if you think you may have a medical emergency.