Unithroid (levothyroxine) is a prescription drug used to treat certain thyroid gland conditions. The drug comes as an oral tablet. It’s usually taken once per day.

Unithroid is used in adults and children to:

The active ingredient in Unithroid is levothyroxine. (An active ingredient is what makes a drug work.) Unithroid belongs to a group of drugs called thyroid hormones.

This article describes the dosages of Unithroid, as well as its strengths and how to take it. To learn more about Unithroid, see this in-depth article.

This section describes the usual dosages of Unithroid. Keep reading to learn more.

What is Unithroid’s form?

Unithroid comes as an oral tablet.

What strengths does Unithroid come in?

Unithroid is available in the following strengths:

  • 25 micrograms (mcg)
  • 50 mcg
  • 75 mcg
  • 88 mcg
  • 100 mcg
  • 112 mcg
  • 125 mcg
  • 137 mcg
  • 150 mcg
  • 175 mcg
  • 200 mcg
  • 300 mcg

What are the usual dosages of Unithroid?

Your doctor will likely start you on a low dosage and adjust it over time to reach the right amount for you. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

The information below describes dosages that are commonly used or recommended. But be sure to take the dosage your doctor prescribes for you. They’ll determine the best dosage to fit your needs.

Dosage for hypothyroidism

The dosage of Unithroid for adults with hypothyroidism depends on your body weight and your thyroid hormone levels. The typical* starting dosage is about 1.6 mcg per kilogram (kg) of body weight taken once daily.

Your doctor will likely order tests to check your thyroid hormone levels every few weeks when you start treatment. And they’ll likely adjust your Unithroid dosage until your thyroid hormones are in the correct range.

* Your doctor may prescribe a different starting dosage in certain cases. See the “Dosage adjustments” section below for more information.

Dosage for TSH suppression

Unithroid is used to lower thyroid stimulating hormone (TSH) levels in adults with thyroid cancer. This is called TSH suppression. The dosage you’re prescribed for this use will depend on your TSH levels and the treatment plan your doctor recommends. They may adjust your Unithroid dosage every few weeks until your TSH levels are in the right range for you.

What’s the dosage of Unithroid for children?

Unithroid is used to treat hypothyroidism in children of all ages. It’s also used to lower TSH levels in children with thyroid cancer. This is called TSH suppression.

The dosage for TSH suppression in children depends on the child’s treatment plan. Their doctor will prescribe the dosage that’s right for the child.

The dosage for treating hypothyroidism in children depends on the child’s age and body weight. Typical starting dosages are shown in the table below.

0–3 months10–15 mcg/kg once daily
3–6 months 8–10 mcg/kg once daily
6–12 months6–8 mcg/kg once daily
1–5 years5–6 mcg/kg once daily
6–12 years4–5 mcg/kg once daily
older than 12 years but before puberty and still growing2–3 mcg/kg once daily
older than 12 years, with puberty and growth complete1.6 mcg/kg once daily

Their doctor will likely order tests to check the child’s thyroid hormone levels every few weeks when they start treatment. And they may adjust the child’s dosage as needed.

For more information about Unithroid’s dosage for children, talk with the child’s doctor or a pharmacist.

Is Unithroid used long term?

Yes, Unithroid is usually used as a long-term treatment. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely take it long term.

Dosage adjustments

You may be prescribed a lower than usual starting dosage of Unithroid in certain cases. These include if you:

  • are age 65 years or older
  • have heart disease
  • have had severe hypothyroidism for a long time

Doctors may also prescribe a starting dosage of Unithroid that’s lower than usual for certain children. These include newborns at risk of heart failure and older children with hyperactive behavior.

Your doctor will likely order blood tests to check your thyroid hormone and TSH levels throughout your treatment. And they may adjust your Unithroid dosage until these levels are in the right range for you.

Your doctor may also adjust your dosage based on other factors. Examples of these are listed in the section just below.

The dosage of Unithroid you’re prescribed may depend on several factors. These include:

  • the type and severity of the condition you’re taking the drug to treat
  • your age
  • your body weight
  • other conditions you may have (see the “Dosage adjustments” section above)
  • if you’re pregnant or breastfeeding
  • other medications you take
  • side effects you may have with Unithroid

Unithroid is available as an oral tablet. If you have trouble swallowing tablets, see this article for tips on how to take this form of medication. You can also crush Unithroid for adults and children who can’t swallow tablets. In this case, you should mix the freshly crushed tablet in 1–2 teaspoons of water. Administer this right away using a spoon or dropper.

Unithroid should be taken without food on an empty stomach, 30–60 minutes before breakfast. Taking it with food can reduce the absorption of the drug into your body, making it less effective.

You should avoid drinking caffeine or calcium-containing drinks, such as tea, coffee, or milk for 30–60 minutes after taking Unithroid. And you should avoid giving children soybean-based infant formula for 30–60 minutes after they take their dose. These drinks can reduce the absorption of Unithroid and make it less effective.

You should not take certain other medications in the 4 hours before and after taking Unithroid. If you take other medications, talk with your doctor or pharmacist about when to take them in relation to Unithroid.

You can also talk with your doctor or pharmacist if you have any other questions about how to take this medication.

Accessible drug containers and labels

Some pharmacies provide medication labels that:

  • have large print
  • use braille
  • feature a code you can scan with a smartphone to change the text to audio

Your doctor or pharmacist may be able to recommend pharmacies that offer these accessibility features if your current pharmacy doesn’t.

Let your pharmacist know if you have trouble opening medication bottles. They may have tips to help, or they may be able to supply Unithroid in an easy-open container.

If you miss a dose of Unithroid, take it as soon as you remember. But if it’s almost time for your next dose, skip the missed dose and take your next dose at its usual time. If you’re not sure whether you should take a missed dose, talk with your doctor or pharmacist.

If you need help remembering to take your dose of Unithroid on time, try using a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.

Do not take more Unithroid than your doctor prescribes, as this can lead to harmful effects.

Symptoms of overdose

Symptoms caused by an overdose can include:

What to do in case you take too much Unithroid

Call your doctor right away if you think you’ve taken too much Unithroid. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

Taking Unithroid can lead to physical dependence, which means your body relies on the drug to function as usual.

Stopping Unithroid won’t cause withdrawal symptoms. (Withdrawal symptoms are side effects you may have if you stop taking a drug your body depends on.) But stopping Unithroid can make the symptoms of your condition come back or get worse.

You should not stop taking Unithroid unless your doctor recommends it.

Below are answers to some commonly asked questions about Unithroid’s dosage.

Are Unithroid’s dosages similar to those of Synthroid (levothyroxine)?

Yes, Unithroid’s dosages are similar to Synthroid’s dosages. These medications contain the same active ingredient levothyroxine. (An active ingredient is what makes a drug work.)

Both drugs come as oral tablets, are available in the same strengths, and are taken once per day.

To learn more about how these drugs compare, talk with your doctor. They’ll prescribe the drug and the dosage that’s right for you.

How long does it take for Unithroid to start working?

Unithroid starts to work after your first dose. But it may take several weeks before your symptoms start to get better. Your doctor will monitor your condition throughout your Unithroid treatment to make sure the drug is working effectively. Be sure to ask them any other questions you have about what to expect from Unithroid treatment.

The sections above describe the usual dosages provided by the manufacturer of Unithroid. If your doctor recommends this drug, they’ll prescribe the dosage that’s right for you. You should not change your dosage of Unithroid without their recommendation. Only take this drug exactly as prescribed.

Talk with your doctor if you have questions or concerns about your current dosage. Here are some examples of questions you may want to ask them:

  • Do I need to take my other medications at a different time of day than Unithroid?
  • Will I have side effects if I miss a dose of Unithroid?
  • If I have side effects from this medication will you decrease my dosage?

To learn more about Unithroid, see these articles:

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Disclaimer: Healthline 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.