Levothyroxine sodium is a prescription thyroid medication. It is actually a synthetic version of a naturally occurring thyroid hormone. Levothyroxine is approved to treat an
underactive thyroid (known medically as
hypothyroidism). It is also approved for the treatment of a variety of other thyroid problems, including certain
types of thyroid cancer.
Side Effects of Levothyroxine
As with any medicine, side effects are possible with levothyroxine. However, not everyone who takes the drug will experience side effects. In fact, most people tolerate it quite well. Serious side effects are less common.
Some of the possible side effects include but are not limited to:
(Click Levothyroxine Side Effects to learn more, including potentially serious side effects you should report immediately to your healthcare provider.)
What Should I Tell My Healthcare Provider?
You should talk with your healthcare provider prior to taking levothyroxine if you have:
Also, let your healthcare provider know if you are:
Make sure to tell your healthcare provider about any other medicines you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.
How Does Levothyroxine Work?
The thyroid gland makes two similar (although slightly different) thyroid hormones: triiodothyronine (T3) and levothyroxine (T4). Usually, the thyroid gland produces much more T4 than T3 (however, T3 is much more active in the body than T4). The body can convert the T4 hormone into the T3 hormone as necessary. If your thyroid does not make enough thyroid hormones, there are a few different ways to increase your levels.
Some forms of thyroid replacement combine both T
3 and T
4 (such as natural thyroid replacement made from pig thyroids). However, because the body converts T
4 into T
3 as needed, most people can successfully take just T
4 (such as levothyroxine). This is the most common type of thyroid replacement. Another option includes taking just T
3 hormones (such as
Cytomel®).
Although it is synthetic, levothyroxine is identical to the naturally occurring hormone T4.
Some general considerations for when and how to take levothyroxine include the following:
- The medication comes in tablet form and is usually taken once daily in the morning.
- It is best to take your dosage on an empty stomach, 30 to 60 minutes before breakfast (if you eat breakfast). This prevents levothyroxine from interacting with food.
- The tablets may be crushed and mixed with one or two teaspoons of water. This mixture must be taken immediately (it should not be stored).
- Your healthcare provider will adjust your levothyroxine dosage based on certain blood tests. Be sure to tell him or her if you have missed any of your doses, as this may affect any dose adjustments.
- Try to take your dose at the same time each day to keep an even level in your blood.
- For the medication to work properly, it must be taken as prescribed. Levothyroxine will not work if you stop taking it.
The dose of levothyroxine your healthcare provider recommends may vary, depending on a number of factors, including:
- Your age
- How you respond to the drug
- The results of certain thyroid blood tests
- Any other medications you are taking
- Other medical conditions you may have.
As is always the case, do not adjust your dose unless your healthcare provider specifically instructs you to do so.
What If I Take an Overdose of Levothyroxine?
People who take too much levothyroxine may have overdose symptoms that can include:
What Should I Do If I Miss a Dose?
If you forget to take your levothyroxine, take your missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take a double dose. Each time you get your blood tests to monitor your thyroid function, be sure to tell your healthcare provider if you have missed any doses, as this may affect any dose adjustments.
Levothyroxine tablets come in the following strengths:
- Levothyroxine 25 mcg
- Levothyroxine 50 mcg
- Levothyroxine 75 mcg
- Levothyroxine 88 mcg
- Levothyroxine 100 mcg
- Levothyroxine 112 mcg
- Levothyroxine 125 mcg
- Levothyroxine 137 mcg
- Levothyroxine 150 mcg
- Levothyroxine 175 mcg
- Levothyroxine 200 mcg
- Levothyroxine 300 mcg.
Sometimes, the strengths are given in milligrams (mg) instead of micrograms (mcg), which can be confusing. Because there are 1000 mcg in every mg, levothyroxine 100 mcg is the same thing as levothyroxine 0.1 mg.
Brand-Name Levothyroxine Products
Brand-name levothyroxine products are sold under several different names. Some of the most popular brand-name products include:
A variety of different generic products are also available. Not all levothyroxine products are equivalent to each other
(see Generic Levothyroxine for more information).
