What is Unithroid: Uses, Warnings & Interactions

Medically reviewed by Karen BergerPharm.D.
Licensed Pharmacist
Updated Dec 8, 2023  •  Published Dec 30, 2020
Fact Checked

Unithroid overview

BRAND NAMES:

  • Unithroid, Tirosint, Synthroid, Euthyrox, Levoxyl

Generic Names:

  • Levothyroxine sodium

  • Levothyroxine

Uses:

  • Treats:

    • Hypothyroidism (a condition where the body does not produce enough thyroid hormone)

    • Thyrotropin-dependent well-differentiated thyroid cancer (in combination with surgery and radioactive iodine)

Therapeutic Classes:

Forms:

  • Tablet

How it’s taken:

  • By mouth

What is Unithroid used for?

Unithroid is FDA-approved to treat:

  • Hypothyroidism (underactive thyroid)

  • Thyrotropin-dependent well-differentiated thyroid cancer (in combination with surgery and radioactive iodine)

Unithroid should never be used to treat obesity or for weight loss. Unithroid also should not be used to treat myxedema coma, a life-threatening emergency. For myxedema coma, injectable thyroid medications must be used.

  • Before taking Unithroid, read the prescription label and patient information leaflet carefully. Ask your healthcare provider or pharmacist if you have any questions.

  • Take Unithroid once a day, at the same time every day. 

  • Take Unithroid on an empty stomach 30 to 60 minutes before breakfast. Swallow the tablet whole with a full, 8-ounce glass of water. 

  • It may take a few weeks before you notice any changes in symptoms. Keep taking your medication as directed by your healthcare professional. 

  • Follow your doctor’s instructions for follow-up appointments and bloodwork. Regular monitoring is important to make sure your thyroid hormone levels are regulated. Your doctor will order bloodwork to test your levels of thyroid-stimulating hormone (TSH levels) and thyroxine (T4).

What form(s) does Unithroid come in

  • Tablet

    • 25 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 common Unithroid doses?

  • The starting dose of Unithroid depends on various factors, including age, body weight, cardiovascular status, other medical conditions, other medications you take, and the condition being treated.

  • Generally, treatment is started at 12.5 mcg (half of a 25 mcg tablet) or 25 mcg daily. The dosage is adjusted every 2 to 4 weeks, if needed, by the healthcare provider. Follow your healthcare provider’s instructions carefully. Do not take more or less medication than prescribed. 

  • Take Unithroid once a day on an empty stomach, 30 to 60 minutes before breakfast. Swallow the tablet whole, and take it with a full glass of water.

  • Your healthcare professional will order blood work periodically to see if the dose is appropriate or if a dosage adjustment is required.

Common Unithroid prescriptions

  • Unithroid
    100mcg tablet

  • Unithroid
    112mcg tablet

  • Unithroid
    125mcg tablet

  • Unithroid
    137mcg tablet

  • Unithroid
    150mcg tablet

  • Unithroid
    175mcg tablet

  • Unithroid
    200mcg tablet

  • Unithroid
    25mcg tablet

  • Unithroid
    300mcg tablet

  • Unithroid
    50mcg tablet

  • Unithroid
    75mcg tablet

  • Unithroid
    88mcg tablet

How to take Unithroid

  • Take your medicine as directed. 

  • Your doctor will tell you how much to take and how often.

  • Your dose may need to be changed several times to find what works best for you. 

  • You may have to take this medicine for 4 to 8 weeks before your symptoms improve.

  • Take this medicine in the morning on an empty stomach, at least 30 to 60 minutes before eating breakfast. Swallow the tablet whole, and take it with a full, 8-ounce glass of water.

  • Take your medicine at the same time every day.

  • Store the medicine at room temperature, away from heat, moisture, and direct light. Keep this and all medicine out of the reach and out of sight of children and pets. Keep the bottle tightly closed when not in use. Never share your medicine with anyone, even if they have the same symptoms.

  • Do not stop taking this medicine without first checking with your doctor. Many people need to take this medication as a lifelong treatment.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

What to do if you miss a dose of Unithroid

  • Take the missed dose as soon as possible.

  • Skip the missed dose if it is almost time for your next regular dose.

  • You should not use two doses at the same time to try to make up for a missed dose.

Unithroid contraindications

Do not use Unithroid if you: 

  • Are allergic to levothyroxine or any active ingredients in the medication

  • Have an uncorrected adrenal gland problem

  • Have had a recent heart attack

Unithroid warnings

  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.

  • Tell your doctor if you have recently received radiation treatment with iodine.

  • Tell your doctor about all the medical conditions you have. Check with your doctor before taking this medicine if you have:

  • This medicine may cause heart problems, including angina (chest pain), heart rhythm problems, or heart attack—if the dose is too high. It is very important to follow your doctor’s instructions on when to get blood work so your levels can be monitored closely.

  • This medicine should not be used to treat obesity or as part of a treatment plan for a weight control program.

  • Large doses of thyroid hormones, especially when taken with diet pills, can result in dangerous adverse effects.

  • Tell any doctor or dentist who treats you that you are taking this medicine.

  • Make sure you see your doctor for regular check-ups so your condition can be followed closely.

  • Your doctor will order lab tests at regular intervals to check on the effects of this medicine and make sure you are taking the proper dosage. Keep all appointments.

  • Do not stop using this medicine suddenly.

Unithroid interactions

  • Some foods and medicines can affect how levothyroxine works. Before taking Unithroid, tell your doctor about all of the medications you take, including prescription drugs, OTC medicines, vitamins, and supplements. Be sure to tell your doctor if you are using any of the following:

  • There are also some drug interactions that interfere with Unithroid’s absorption. These medications should be taken at least 4 hours before or 4 hours after you take Unithroid, such as:

    • Kayexalate (sodium polystyrene sulfonate)

    • Lanthanum

    • Orlistat

    • Sevelamer

    • Sucralfate

    • Antacids that contain aluminum or magnesium, such as Maalox, Mylanta, Milk of Magnesia, magnesium hydroxides

    • Simethicone

    • Any medicine that contains iron (such as iron or ferrous sulfate products) or calcium, such as antacids that contain calcium carbonate

    • Certain medicines that lower cholesterol (including cholestyramine, colesevelam, and colestipol)

    • Proton pump inhibitors (including lansoprazole, omeprazole, esomeprazole, rabeprazole, pantoprazole, Nexium, Prilosec, Zegerid)

  • Cottonseed meal, soybean flour (infant formula), walnuts, grapefruit, grapefruit juice, and high-fiber foods may decrease the absorption of this medicine. Consult your doctor for medical advice about dietary restrictions.

  • Large doses of thyroid hormones, especially when taken with diet pills, can result in dangerous side effects.

Unithroid side effects

Serious side effects may occur. If you have symptoms of an allergic reaction, get emergency medical help. Symptoms of an allergic reaction may include skin rash, hives, trouble breathing, or swelling of the face, lips, tongue, or throat. Call your physician right away (or get emergency medical help if your symptoms feel life-threatening or you think you are having a medical emergency) if you have any other serious side effects, such as: 

  • Seizures

  • Fast, pounding, or uneven heartbeat

  • Chest pain that may spread to the jaw or shoulder

  • Memory problems

  • Feeling very cold

  • Unusual tiredness or weakness

  • Trouble sleeping

  • Headache

  • Muscle pain

  • Leg cramps

  • Dry skin or hair

  • Hair loss

  • Irregular menstrual cycles

  • Stomach pain

  • Fever, hot flashes, intense sweating, inability to tolerate heat

  • Nervousness or irritability

  • Depression

  • Tremors

  • Vomiting or diarrhea

  • Changes in weight and/or appetite

Common side effects:

  • Anxiety or irritability

  • Chest pain

  • Irregular heartbeat

  • Leg cramps

  • Tremors

  • Feeling hot 

  • Irregular menstrual periods

  • Headache

  • Trouble sleeping

  • Hair loss

  • Appetite or weight changes

  • Diarrhea

  • Muscle pain or weakness

  • Sensitivity to heat

Sources:

Medically reviewed by Karen BergerPharm.D.
Licensed Pharmacist

After receiving her doctorate from the University of Pittsburgh School of Pharmacy, Karen Berger, Pharm.D., has worked in both chain and independent community pharmacies. She currently works at an independent pharmacy in New Jersey. Dr. Berger enjoys helping patients understand medical conditions and medications—both in person as a pharmacist, and online as a medical writer and reviewer.

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