Prescription onlyLower-cost generic availableClass: Endocrine



Prescription onlyLower-cost generic availableClass: Endocrine
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Replaces thyroid hormones.

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Our bottom line

Synthroid (Levothyroxine) is an important replacement hormone when your body can't make enough thyroid hormone. It's easily affected by food, other medicines or supplements, and health conditions, so you should try to take it exactly as instructed.

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  • Supplies an essential hormone that your body needs to function. Works well to improve symptoms of an underactive thyroid.
  • Safe to use for any age range and pregnant women.
  • Cheap.
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  • Absorption is easily affected by food and other medicines.
  • Not one-dose-fits-all: Dose adjustments are usually needed when starting the medicine and when your health changes.
  • Routine blood tests are needed at least yearly and more during dose adjustments, but it takes a long time to see full effect (6 to 8 weeks).
  • Different brands of Levothyroxine may not work the same. Ask your pharmacist if your refill looks different than your old pills. Synthroid is one of the few drugs where the brand really does work better than the generic for many people.
  • Lots of drug interactions, so check with your pharmacist before taking anything new.
How it works

Synthroid (Levothyroxine) is a synthetic version of a hormone made by your thyroid gland. Thyroid hormones affect many important bodily functions, like controlling metabolism and telling your body how to use energy sources.

What to expect when you take Synthroid (levothyroxine) for Thyroid supplement

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Side effect rates for Synthroid (levothyroxine)

Risks and Warnings for Synthroid (levothyroxine)

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    • Higher risk if:
    • Current heart disease
    • Age 60 or older
    • Taking Synthroid (Levothyroxine) with certain types of stimulant medicines

    Taking Synthroid (Levothyroxine) can cause new or worsen heart problems. Call your doctor or get medical care right away if you have rapid or irregular heartbeats, chest pain or shortness of breath. These symptoms may be serious and due to overtreatment of Synthroid (Levothyroxine). You may need to stop taking your medicine for one week, then re-start at a lower dose.

Means that some groups have a high risk of experiencing this side effect

Common concerns from people taking Synthroid (levothyroxine)

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  • Lots of drug interactions, so check with your pharmacist before taking anything new.
  • Many medicines interact with Synthroid (Levothyroxine). You may need your dose adjusted, especially if they are "narrow" therapy medicines like warfarin. Let your doctor and pharmacist know if you are taking any new prescriptions or over-the-counter medicines.
  • Food prevents Levothyroxine absorption. Take it on an empty stomach with a full glass of water at least 30 minutes before breakfast and other medicines. If this is too much of a hassle for you and you end up skipping your medicine, it's better to just take it whenever you want, and your doctor can increase the dose if needed.
  • Having to take it early, before coffee or breakfast, is inconvenient, but totally worth it when you get your energy back. Also, I found that it didn't work nearly as well for me till I started regulating my blood sugar through better diet choices. I don't feel hypo any more!
  • Sometimes it is really hard to take it early enough before breakfast.
  • don't take Synthroid (Levothyroxine) for weight loss or obesity. It’s not recommended, safe or effective for this use, especially if you don't have any issues with your thyroid. Taking high doses of Synthroid (Levothyroxine) can cause serious or fatal effects especially if used with other medications for weight loss. Talk to your doctor before about other medicines you can take to treat your condition.
  • It takes time to take effect & the weight gained because of a slow thyroid did not just fall off-took me 5 years to lose.