Levothyroxine oral tablets dosage

Key takeaways

• The correct dosage of levothyroxine varies for adults and children, depending on the condition being treated, age, weight, and thyroid hormone levels levels, so it’s important to follow a doctor’s specific instructions.
• Levothyroxine tablets should be taken once daily on an empty stomach, 30 to 60 minutes before the first meal, and the tablets should not be split or chewed for best absorption.
• Levothyroxine should not be used as a weight loss aid, and overdosing can lead to serious side effects, necessitating immediate consultation with a healthcare professional.

Overview

Levothyroxine oral tablets are a generic medication for the brand names Euthyrox, Levo-T, Levolet, Levoxyl, Synthroid, and Unithroid. This article describes levothyroxine’s dosages, strengths, and details on how to take it.

If you want to know more about levothyroxine, see this overview article. It covers details about the drug’s uses, side effects, ways to save on cost, and more.

Levothyroxine has a boxed warning about not using it to aid in weight loss or to treat obesity. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the end of this article.

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Form and strengths of levothyroxine

Levothyroxine oral tablets come as follows:

• Form: a tablet that you swallow
• Strengths:
  • 25 micrograms (mcg)
  • 50 mcg
  • 75 mcg
  • 88 mcg
  • 100 mcg
  • 112 mcg
  • 125 mcg
  • 137 mcg
  • 150 mcg
  • 175 mcg
  • 200 mcg

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Dosage of levothyroxine

This article describes the usual recommended dosages for levothyroxine oral tablets. In some cases, doctors may adjust your dosage from those shown below.

If your doctor prescribes this medication, they’ll determine the dosage that’s best for you. Do not change your dosage of levothyroxine oral tablets without your doctor’s recommendation.

Usual recommended dosages of levothyroxine in adults

Usually, doctors will start by prescribing a low dosage of levothyroxine oral tablets. Then, they’ll adjust the dosage over time until they reach the right dosage. Ultimately, your doctor will prescribe the smallest dosage of levothyroxine oral tablets that gives the desired outcome.

Doctors prescribe levothyroxine in micrograms (mcg). This is unlike most other drugs, which are prescribed in milligrams (mg).

The dose depends on your body weight in kilograms (kg). (For reference, 1 kg equals about 2.2 pounds.) Your doctor will prescribe levothyroxine oral tablets as mcg per kg body weight per day (mcg/kg/day).

The dosage chart below describes levothyroxine’s recommended dosages for adults:

During levothyroxine treatment, your doctor will order blood tests to check the TSH level in your body. They’ll adjust your levothyroxine dose based on these test results.

Note that it’s rare that dosages greater than 200 mcg are necessary. If there is an inadequate response to a dosage greater than 300 mcg, this indicates that other factors may be affecting your condition.

Dosages of levothyroxine in children

Levothyroxine is prescribed to treat hypothyroidism in children. Doctors determine children’s doses by the child’s body weight and age. For this purpose, doctors will determine children’s doses based on their TSH level. See the dosage table below for specifics.

Levothyroxine is also prescribed to treat certain kinds of thyroid cancer in children. For treating thyroid cancer, doctors will also determine doses based on a child’s TSH levels.

Levothyroxine dosage table by weight and age

The dosage table below describes levothyroxine dosage for treating hypothyroidism in children by weight and age.

Dosage adjustments for levothyroxine

Your doctor will prescribe a dosage of levothyroxine oral tablets based on several factors, including:

• the specific condition being treated and its severity
• your age
• your body weight
• other health conditions you may have, including:
  • heart disease
  • hyperactivity (in children)

Frequently asked questions

Below are answers to some commonly asked questions about levothyroxine oral tablets and their dosage.

What should I know about calculating levothyroxine doses?

Levothyroxine doses are calculated using your body weight in kilograms (kg). (For reference, 1 kg equals about 2.2 pounds.)

Your doctor may use a dose calculator to determine your levothyroxine dose. A dose calculator helps doctors quickly calculate your starting dose based on the recommended dose for your weight.

Will my doctor be adjusting my levothyroxine dose based on my TSH level? Are there adjustment guidelines to follow?

Yes, your doctor will adjust your levothyroxine dose based on your thyroid stimulating hormone (TSH) level.

While you’re taking levothyroxine, your doctor will order blood tests to check your TSH level. Your doctor may adjust your dose every 4 to 6 weeks based on your test results. Always follow your doctor’s instructions for lab tests and dosage.

What is the lowest dose, highest dose, and ‘normal’ dose of levothyroxine?

The lowest available dosage of levothyroxine oral tablets is 25 micrograms (mcg) per day. The highest dosage is 300 mcg per day.

There’s no “normal” dose for levothyroxine. A person’s levothyroxine dose depends on the level of thyroid stimulating hormone (TSH) in their body. (See the question about TSH just above to learn more.) It also varies based on age and body weight.

Is levothyroxine used long term?

Yes, doctors typically prescribe levothyroxine oral tablets as a long-term treatment.

If you and your doctor determine that it’s safe and effective for your condition, you’ll likely take the medication long term.

What should I do for a missed dose of levothyroxine?

If you realize you forgot to take a dose of levothyroxine, tell your doctor or pharmacist right away. They may advise you to take the missed dose. Or they may advise you to skip it and take your next dose as scheduled.

For tips on how to plan your doses of levothyroxine and avoid missing a dose, read this article. You could also try:

• downloading a reminder app on your phone
• setting an alarm
• putting a note where you’ll see it, such as on your calendar, bathroom mirror, or bedside table

How levothyroxine is taken

Levothyroxine oral tablets are taken by mouth. They’re taken once per day.

You should take levothyroxine on an empty stomach, preferably 30 to 60 minutes before your first meal of the day. This can help the drug work more effectively because it keeps a consistent amount of the drug in your body.

Do not split or chew the tablets. If it’s hard for you to swallow tablets, you may crush them. Then, mix them with 1–2 teaspoons of water. Swallow the mixture immediately.

Get tips in this article on how to swallow medications that come in pill form.

Also, be sure to talk with your doctor or pharmacist if you’re having difficulty taking your medication. They can offer recommendations about taking it.

Overdose of levothyroxine

It’s important that you do not take more levothyroxine oral tablets than your doctor prescribes. Doing so can lead to serious side effects.

Symptoms of levothyroxine overdose

Symptoms caused by an overdose can include:

• excessive sweating
• headache
• feeling anxious or irritable
• tremors (shaky limbs or shakiness)
• muscle spasm
• fast, slow, or irregular heart rate
• feeling confused or disoriented
• heart attack
• cardiac arrest
• bleeding in your head
• shock
• coma

In rare cases, death has occurred due to levothyroxine overdose.

What to do in case you take too much levothyroxine

If you think you’ve taken too much levothyroxine, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have severe symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Boxed warning

Levothyroxine has a boxed warning about not using it to aid in weight loss or to treat obesity. Boxed warnings are serious warnings from the Food and Drug Administration (FDA).

Levothyroxine should not be used for weight loss or treating obesity. Recommended doses of levothyroxine are not effective for weight loss in people with typical thyroid function. And taking more than the recommended doses of this medication can cause serious or even life threatening side effects.

Talk with your doctor for more information about levothyroxine’s boxed warning.

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Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.