Unithroid (levothyroxine) is a prescription drug used to treat certain thyroid diseases. Unithroid comes as an oral tablet.

Unithroid is used in adults and children to:

To learn more about Unithroid’s uses, see the “What is Unithroid used for?” section below.

Unithroid contains the active ingredient levothyroxine. (An active ingredient is what makes a drug work.)

Unithroid is a brand-name medication that’s also available as the generic drug levothyroxine.

Find answers to some commonly asked questions about Unithroid.

How does Unithroid compare with Synthroid?

Both Unithroid and Synthroid are prescribed to treat hypothyroidism and to lower thyroid stimulating hormone (TSH) levels in people with thyroid cancer.

Both drugs come as an oral tablet that contains the active ingredient levothyroxine. (An active ingredient is what makes a drug work.) Because of this, these drugs work in the same way to treat thyroid conditions and have side effects that are very similar.

But because they may have different inactive ingredients, it’s possible for some side effects, such as allergic reaction, to be different.

If you have other questions about how Unithroid and Synthroid compare, talk with your doctor. They can help you find the best treatment for your condition.

Does Unithroid cause long-term side effects?

It’s possible. Long-term side effects include those that may start at any time you’re taking a drug, even if you’ve taken it for a long time. It also includes side effects that may not go away, even after you stop taking the drug.

Examples of long-term side effects reported in Unithroid’s studies include:

Talk with your doctor to learn more about possible long-term side effects of Unithroid and how long they may last.

Like most drugs, Unithroid may cause mild to serious side effects. Listed below are some of this drug’s more common side effects. But these lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you take

Your doctor or pharmacist can tell you more about the potential side effects of Unithroid. They can also suggest ways to help reduce them.

Mild side effects

Below are some of the mild side effects Unithroid can cause. To learn about other mild side effects, talk with your doctor or pharmacist, or check out Unithroid’s prescribing information.

Mild side effects of Unithroid that have been reported include:

Mild side effects of many drugs may go away within a few days to a couple of weeks. But if they become bothersome or are ongoing, talk with your doctor or pharmacist.

* To learn more about this side effect, see the “Allergic reaction” section below.

Serious side effects

Serious side effects from Unithroid can occur, but they aren’t common. If you have serious side effects from this drug, call your doctor right away. But if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects of Unithroid that have been reported include:

* To learn more about this side effect, see the section just below.

Allergic reaction

Some people may have an allergic reaction to Unithroid. Symptoms of a mild allergic reaction can include:

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include:

  • swelling under your skin (usually in your eyelids, lips, hands, or feet)
  • swelling of your tongue, mouth, or throat, which can make it hard to breathe

Call your doctor right away if you have an allergic reaction to Unithroid. But if you think you’re having a medical emergency, call 911 or your local emergency number.

Your doctor will recommend the dosage of Unithroid that’s right for you. Below are commonly used dosages, but always take the dosage your doctor prescribes.

Form and strengths

Unithroid is available as an oral tablet. It’s 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

Recommended dosages

You’ll take your dose of Unithroid once daily. Your doctor will recommend the best dosage for you based on many different factors, such as:

  • your age
  • your body weight
  • other medical conditions you have
  • the type and severity of the condition you’re taking Unithroid for
  • other medications that you take

Dosage for hypothyroidism

For treating hypothyroidism, your doctor will calculate the best starting dosage of Unithroid based on your body weight. They may occasionally order blood tests to check your thyroid levels and adjust your dose of Unithroid based on the results of those tests.

Dosage for TSH suppression

Unithroid is used to decrease thyroid stimulating hormone (TSH) levels in people with thyroid cancer. In this case, your doctor will determine the best dosage of the drug for you. They may then adjust it over time, based on your treatment plan.

To learn more about Unithroid’s dosage, see this article.

Questions about taking Unithroid

Below are some common questions about taking Unithroid.

  • Can Unithroid be chewed, crushed, or split? If you have trouble swallowing pills, you can crush Unithroid tablets and dissolve them in water. However, the manufacturer of Unithroid doesn’t specify if it’s safe to split or chew the tablets. Check out this article if you have trouble swallowing pills and don’t want to crush Unithroid. You can also ask your doctor for tips on how to take this drug or recommendations for a different treatment option.
  • Should I take Unithroid with food? No, you should take Unithroid on an empty stomach with a full glass of water at least 1/2–1 hour before breakfast.
  • Is there a best time of day to take Unithroid? Yes, you should take your dose of Unithroid on an empty stomach 1/2–1 hour before breakfast.
  • What if I miss a dose of Unithroid? If you miss a dose of Unithroid, talk with your doctor or pharmacist about the best time to take your next dose.
  • Will I need to use Unithroid long term? Yes, if Unithroid works for you, your doctor will likely recommend that you take it long term.


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

Symptoms of overdose

Symptoms caused by an overdose can include:

In extreme cases, overdose could lead to coma.

What to do in case you take too much Unithroid

Call your doctor 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.

Unithroid is prescribed for adults and children of any age to:

Hypothyroidism is a condition where your body doesn’t have enough thyroxine (T4). This condition can be caused by many different factors, including Hashimoto thyroiditis or surgical removal of the thyroid gland. Hypothyroidism may cause symptoms such as fatigue (low energy), depression, or weight gain. Unithroid helps treat hypothyroidism by replacing thyroxine in your body.

Unithroid also decreases TSH levels in people with thyroid cancer. Thyroid cancer may cause symptoms such as a lump in your neck, difficulty swallowing, or pain in your throat. By reducing TSH levels, Unithroid helps prevent thyroid cancer cells from growing.

Whether you have health insurance or not, cost may be a factor when you’re considering Unithroid. What you’ll pay for this drug may depend on several things, such as your treatment plan and the pharmacy you use.

Here are a few things to consider regarding cost:

  • Cost information and savings coupons: You can visit Optum Perks* to get price estimates of what you’d pay for Unithroid when using coupons from the site.
  • Generic form: Unithroid is available as the generic drug levothyroxine. Generics usually cost less than brand-name drugs. Talk with your doctor if you’d like to know whether levothyroxine could be an option for you.
  • Savings program: If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. You can also visit this site to learn about the Unithroid Savings Card and a savings program called eVoucher RX.

You can also check out this article to learn more about saving money on prescriptions.

* Optum Perks is a sister site of Healthline. Optum Perks coupons cannot be used with any insurance copays or benefits.

Below is important information you should consider before starting Unithroid.


Taking a drug with certain medications, vaccines, foods, and other things can affect how the drug works. These effects are called interactions. Unithroid can interact with many other medications. It can also interact with certain supplements as well as certain foods.

Before taking Unithroid, talk with your doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

Drug interactions

Below is a list of medications that can interact with Unithroid. (This list does not contain all drugs that may interact with Unithroid.) If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Drug group or drug name Drug examples
sevelamer (Renvela)
bile acid sequestrants• colesevelam (Welchol)
cholestyramine (Prevalite)
• colestipol (Colestid)
proton pump inhibitorsesomeprazole (Nexium)
pantoprazole (Protonix)
antacids• calcium carbonate (Tums)
• aluminum hydroxide/magnesium hydroxide (Maalox)
oral contraceptives • ethinyl estradiol/norethindrone (Junel Fe)
• ethinyl estradiol/norgestimate (Sprintec)
tamoxifen (Soltamox)
methadone (Methadose)
androgenstestosterone (Androgel)
glucocorticoidsdexamethasone (Ozurdex)
prednisone (Rayos)
diabetes medicationsmetformin (Fortamet)
• glyburide (Diabeta)
beta-blockerspropranolol (Inderal)
metoprolol (Toprol XL, Lopressor)
tricyclic antidepressants (TCAs)amitriptyline
doxepin (Zonalon)
some blood thinner drugsheparin
warfarin (Jantoven)
furosemide (Lasix)
digoxin (Lanoxin)
certain seizure medications• phenobarbital
carbamazepine (Tegretol)
rifampin (Rimactane)
amiodarone (Pacerone)

Other interactions

Unithroid can also interact with other substances such as:

  • Vitamins or supplements: Unithroid interacts with iron, calcium, and certain vitamins that contain iron or calcium. Your doctor may recommend that you avoid taking these vitamins or supplements during Unithroid treatment.
  • Foods: Unithroid may interact with soybean flour (found in infant formula), cotton seed meal, walnuts, and dietary fiber. Your doctor may recommend that you do not eat these foods during Unithroid treatment. In some cases, your doctor may recommend adjusting your dose of the drug. Unithroid also interacts with grapefruit and grapefruit juice. Your doctor will likely recommend that you do not consume grapefruit products during your Unithroid treatment.
  • Alcohol: Alcohol is not known to interact with Unithroid. It’s likely safe to consume alcohol while taking this medication.

Pregnancy and breastfeeding

Unithroid is considered safe for use during pregnancy. Studies have shown no increase in problems with fetal development (commonly known as birth defects) or miscarriage in people who took Unithroid during pregnancy. And untreated hypothyroidism during pregnancy may cause risks to the mother and fetus.

It’s not known whether it’s safe to take Unithroid while breastfeeding. It’s believed that the drug passes into breastmilk. But it’s not known what effects the drug may have on a breastfeeding baby. If you’re breastfeeding, or planning to breastfeed, talk with your doctor before starting Unithroid treatment.

Birth control

Some birth control pills may make Unithroid less effective, which means Unithroid may not work as well to treat thyroid disease. If you’re taking birth control pills, talk with your doctor before starting Unithroid. They can recommend contraception that doesn’t interact with Unithroid.

Boxed warning

Unithroid has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Unithroid has a boxed warning about the drug not being used to treat obesity or as a weight loss aid.

Unithroid may not cause weight loss in people who don’t have a thyroid condition. And Unithroid taken in high doses can cause serious or even life threatening side effects, such as confusion or disorientation. In some cases, it could even lead to coma.

Your doctor will not recommend Unithroid for weight loss. If you’re interested in a weight loss aid or a treatment for obesity, ask them to recommend safe options.


Unithroid can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Unithroid is a good treatment option for you.

Talk with your doctor about your health history before starting Unithroid. Be sure to tell them if any of the following factors apply to you:

Other drugs are available that can treat your condition. If you’d like to explore alternatives to Unithroid, talk with your doctor. They can tell you about other medications that might work well for you.

The following drugs are similar to Unithroid:

  • liothyronine (Cytomel)
  • desiccated thyroid (Armour Thyroid)
  • other brands of levothyroxine (Levoxyl, Synthroid, Tirosint)

If you have questions about Unithroid, talk with your doctor or pharmacist. Questions you may want to ask include:

  • If Unithroid isn’t working for me, can my dose be increased?
  • How should I manage side effects of Unithroid?
  • If I become pregnant while I’m taking Unithroid, does my dose need to change?
  • Do any of the other medications I take interact with Unithroid?

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

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.