What is this medication for?
Levothyroxine is a thyroid hormone supplement that is most commonly used to treat people who do not produce enough thyroid hormone on their own. Levothyroxine helps reduce the symptoms of low thyroid hormone such as weight gain, sensitivity to cold, lack of energy, and dry skin. It may take 4 to 6 weeks for this medication to have a noticeable effect on your condition.
Your doctor may have suggested this medication for conditions other than those listed here. As well, some forms of this medication may not be used for all of the conditions discussed here. If you are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.
Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.
What form(s) does this medication come in?
Synthroid® is available as:
- tablets
- 25 µg
- 50 µg
- 75 µg
- 88 µg
- 100 µg
- 112 µg
- 125 µg
- 137 µg
- 150 µg
- 175 µg
- 200 µg
- 300 µg
Some medications may have other generic brands available. Always ask your doctor or pharmacist about the safety of switching between brands of the same medication.
How should I use this medication?
The dose of levothyroxine depends on how much of the hormone is needed to
bring blood levels to within the normal range. This is determined by blood
tests that are done in a laboratory. The starting dose will depend on the general
physical condition of the person taking the medication and the severity and
how long symptoms of low thyroid hormone levels have been present.
This medication is taken once a day at the same time every day, preferably
on an empty stomach, one-half to one hour before breakfast. It should be taken
at least 4 hours apart from medications that are known to interfere with its
absorption (see "What medications can interact with this medication?").
Signs that you may be getting too much thyroid hormone may include chest pain, increased heart rate, palpitations, excessive sweating, heat intolerance, and nervousness. If you think your dose of thyroid hormone may be too high, consult your doctor as soon as possible.
Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.
It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.
Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.
Who should NOT take this medication?
Levothyroxine should not be taken by anyone who:
- is allergic to levothyroxine or to any of the ingredients of the medication
- is in the acute recovery phase following a heart attack
- has untreated or acute thyrotoxicosis (too much thyroid hormone in their system)
- has uncorrected adrenal insufficiency
