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Levothyroxine Side Effects, Dosage & Additional Considerations

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Levothyroxine Side Effects, Dosage & Additional Considerations

writtenByWritten by: Leah McCabe
Leah McCabe

Leah McCabe

Leah likes writing about health and science subjects. Through her writing she hopes to help people of all backgrounds have equal access to information and quality healthcare.

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December 9, 2020 Read Time - 5 minutes

Levothyroxine Side Effects, Dosage & Additional Considerations

Levothyroxine is a prescription medication used to treat hypothyroidism. At times, Levothyroxine is also used to treat goiter and certain forms of thyroid cancer. It is sold under the brand names Eltroxin, Levoxyl, Synthroid, and Unithroid. There are three types of levothyroxine prescribed, namely an oral tablet, a capsule, and an injectable solution. It works by supplementing the body with thyroid hormones as if it produced them naturally by itself.

Levothyroxine Dosage

Depending on your dosage, you may need to take more than one tablet. Levothyroxine is supplied in three variations. There is a 25, 50 and 100 microgram tablet available. The starting dose for most people is between 50 and 100 micrograms taken once per day. This dosage will increase gradually, reaching a dose ranging between 100 and 200 micrograms over the course of a few weeks to months.

Older patients and those suffering from cardiovascular disorders or heart disease are prescribed Levothyroxine as a liquid instead. If you are taking tablets, then check whether they are water-soluble or not. Certain brands require you to swallow the tablet whole with water, while others like Eltroxin ask for the pill to be dissolved first.

Levothyroxine Side Effects

Most side effects arise due to the dosage of Levothyroxine being too high. Your medical professional will be able to prescribe the best dose based on your individual blood test results. When you first begin supplementing with Levothyroxine, you can expect the following minor side effects as your body adjusts:

  • Heightened levels of concentration
  • Heightened appetite
  • Increased rate of weight loss
  • Frequent sweating
  • Mild headaches
  • Heat sensitivity
  • Hyperactivity
  • Slight nervousness & anxiety
  • Mood swings
  • Fatigue
  • Insomnia
  • Temporary hair loss
  • Changes to menstruation

These minor symptoms usually subside within the first few days to weeks of treatment. There are, however, also more serious side effects that can arise. Most of this stems from taking too much Levothyroxine. The side effects of taking too much levothyroxine signaling that you need a lower dosage are:

  • Constant nausea
  • Frequent diarrhea
  • Persistent headaches
  • Hot flushes
  • Muscle cramps
  • Trembling & shaking (especially of the hands)
  • Restlessness or mania
  • Difficulty focusing
  • The general feeling of unrest
  • Shortness of breath
  • Swelling of the feet, ankles or legs
  • Arrhythmia
  • Too high of a heart rate

As you may notice, the side effects of taking too high of a dosage are very similar to having an overactive thyroid, or hyperthyroidism.

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What If I Forget to Take My Hypothyroid Medication?

If you happen to skip a dose then don’t double up on your next one. Take a single dose as soon as you remember but if you find that you forget too often, set an alarm or reminder. You must never take more than a single dose no matter how many days you’ve skipped. Taking multiple tablets at once can lead to side effects such as chest pain or an irregular, racing heartbeat.

Possible Interactions With Other Drugs

Taking any of the following medications/drugs in combination with Levothyroxine can increase the risk of serious side effects:

  • Antidepressants – The combined side effects of popular antidepressants such as sertraline and amitriptyline increase the risk for arrhythmias, or irregular heartbeat
  • Sympathomimetic Drugs – Taking drugs such as pseudoephedrine and albuterol containing stimulant effects will increase the risk of side effects and make you susceptible to developing serious heart complications
  • Blood Thinners – Blood thinners such as Warfarin increase the chances of excessive bleeding. The dosage of your blood thinner will need to be adjusted if you start taking Levothyroxine
  • Ketamine – Taking Ketamine and Levothyroxine will lead to a highly elevated heart rate placing you at risk of a heart attack. It also raises the risk of spurring long-term high blood pressure problems.

What You Need to Know About The Levothyroxine Recall 2018

In 2018, Levothyroxine products experienced a voluntary recall. A Sichuan Friendly thyroid API used to manufacture many Levothyroxine products was detected to have inconsistent levels of levothyroxine and liothyronine. While no adverse reactions were detected from the inconsistent medication, all connected drugs labeled “Thyroid Powder” or “Thyroid Powder USP” have been quarantined.

Later in 2018, another inconsistency was reported whereby Westminster Pharmaceuticals LLC recalled all their unexpired lots of tablets. This was also due to quality deficiencies. The levels of levothyroxine and liothyronine were simply too low to be used as a reliable treatment.

Find the Right Brand and Dosage for Your Thyroid

The best way to have your thyroid tested and to get the right treatment plan is to book a real-time video diagnosis with a PlushCare professional. You can schedule an appointment for a later date or have your needs attended to immediately.

Once the right course of action is determined, our doctors will arrange collection of your prescription medication at the pharmacy closest to you. There is no quicker way to get the right advice to promote a healthy lifestyle and normal thyroid function.

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Most PlushCare articles are reviewed by M.D.s, Ph.Ds, N.P.s, nutritionists and other healthcare professionals. Click here to learn more and meet some of the professionals behind our blog. The PlushCare blog, or any linked materials are not intended and should not be construed as medical advice, nor is the information a substitute for professional medical expertise or treatment. For more information click here.

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