By the Medsmingle Team · Updated 13 November 2026
This is a prescription medicine. Only take it if it has been prescribed for you, and follow your doctor’s and pharmacist’s instructions.
Levothyroxine (Synthroid, Levoxyl and generics) replaces thyroid hormone when your thyroid is underactive (hypothyroidism). Most people take it for life, and getting the timing right makes a big difference.
How to take it
- Once a day, on an empty stomach, with a full glass of water
- Usually 30 to 60 minutes before breakfast; ask your prescriber before changing to a bedtime schedule
- At the same time every day
What can block it
Separate levothyroxine by at least 4 hours from:
- Calcium and iron supplements, multivitamins with minerals
- Certain antacids; ask a pharmacist about timing for each heartburn medicine
- Cholesterol binders such as cholestyramine
Coffee, soy and high-fiber meals can also reduce absorption, so keep these consistent and away from your dose.
Signs your dose may need adjusting
Too high: fast or pounding heartbeat, shakiness, anxiety, sweating, trouble sleeping, weight loss.
Too low: tiredness, feeling cold, weight gain, constipation, dry skin.
Tell your doctor; don’t change the dose yourself.
Blood tests
Your doctor checks TSH about 6 to 8 weeks after starting or changing the dose, then usually once a year.
Important to know
- Tell your doctor if you become pregnant; the dose often needs increasing
- Try to stay on the same brand or generic, as switching can change levels slightly
- Get urgent help for chest pain or a very fast, irregular heartbeat
Frequently asked questions
What if I miss a dose?
Take it when you remember that day. If it’s nearly time for the next one, skip it. Don’t double up unless your doctor says so.
Can I take levothyroxine with coffee?
Wait 30 to 60 minutes after your dose before drinking coffee.
For questions about a prescription or symptoms, speak with your own doctor or pharmacist. For website enquiries, contact our team.
About Medsmingle
Medsmingle (medsmingle.com) shares clear, plain-English information on medicines and everyday health. Explore more health guides and the latest articles, read about us, or contact our team with a question.
This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist.
Source and further reading
MedlinePlus patient medicine information. Read the leaflet for your specific medicine; this overview does not list every warning or interaction.
Do not use thyroid hormone for weight loss. Taking more than prescribed can cause serious harm.
