Drugs Home > Levoxyl Warnings and Precautions

When starting treatment with Levoxyl, warnings and precautions should be fully understood to help prevent any complications. For instance, prior to taking Levoxyl, tell your healthcare provider if you have any heart problems, diabetes, or osteoporosis. Levoxyl warnings and precautions also extend to people who have adrenal insufficiency, an overactive thyroid, or certain allergies.

Levoxyl: What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to taking Levoxyl® (levothyroxine sodium) if you have:
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
Make sure to tell your healthcare provider about any other medicines you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Specific Levoxyl Warnings and Precautions

Some of the warnings and precautions to be aware of prior to taking Levoxyl include the following:
  • Levoxyl is a "narrow therapeutic index" medication. This means that for any given person, the range of Levoxyl doses that are both safe and effective is small. Even tiny changes in doses can cause significant problems (either making Levoxyl ineffective or causing serious side effects).

Your healthcare provider should carefully and slowly adjust your dose, and should monitor your progress often using blood tests. Even if you have been stable on Levoxyl for years, your healthcare provider should still do these blood tests regularly.  

  • The medication can make heart problems worse. If you have heart problems, your healthcare provider should start you at a low Levoxyl dosage and slowly increase it. If you notice that Levoxyl makes your heart symptoms worse, let your healthcare provider know right away.
  • People who do not have thyroid problems should never use Levoxyl to lose weight. A Levoxyl dosage high enough to cause weight loss in these people is often high enough to cause serious or even life-threatening problems.
  • Levoxyl should not be used to treat goiters or thyroid nodules in people who have a low level of thyroid-stimulating hormone (TSH), as it could cause dangerous side effects. A low TSH level signals that thyroid hormone levels are already high, and adding Levoxyl could cause them to increase to a dangerous level. Even if the TSH level is normal, frequent monitoring is required to make sure problems do not develop.
  • Levoxyl may increase the risk of osteoporosis, particularly if your Levoxyl dose is too high. This is one of the reasons why it is a good idea for your healthcare provider to prescribe a dose of Levoxyl that is just enough to return your thyroid hormone levels to normal.
  • Sometimes, thyroid problems occur in conjunction with other health problems (such as anemia or diabetes). It is a good idea for your healthcare provider to give you a thorough physical when you are diagnosed with a thyroid problem.
  • It often takes Levoxyl several weeks to start working. Try not to get frustrated if you are not feeling better more quickly.
  • If you have diabetes, it is a good idea to check your blood sugar more often when starting or stopping Levoxyl (or when changing your dose), as the medication can affect your blood sugar levels.
  • Levoxyl can potentially interact with many other medications (see Levoxyl Drug Interactions).
  • Levoxyl is considered a pregnancy Category A medication. This means that it is probably safe for use during pregnancy (see Levoxyl and Pregnancy).
  • Levoxyl does pass through breast milk in humans, although it is not likely to cause problems. If you are breastfeeding or plan to start breastfeeding, discuss this with your healthcare provider prior to taking the drug (see Levoxyl and Breastfeeding).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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