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Your Definitive Guide to Thyroid Medication

Discover everything you need to know about thyroid medication for hypothyroidism in this guide.
Your Definitive Guide to Thyroid Medication
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The thyroid is the butterfly-shaped gland at the base of your neck. It produces hormones that regulate your body's energy use, helping to power every cell, tissue, gland, organ, and process in the body. 

As part of the endocrine system, the thyroid gland makes and stores hormones that help regulate the body's metabolism, affecting everything from blood pressure, to heart rate, to body temperature. Thyroid hormones are essential for survival.

‍When your thyroid hormone production drops, processes throughout your body slow down and change. Common symptoms of hypothyroidism include cold intolerance, weight gain, dry skin, fatigue, sluggishness, depression, constipation, slowed heart rate, low blood pressure, and heavy menstrual cycles, among others.

The most common cause of hypothyroidism in the United States is Hashimoto's thyroiditis. Hashimoto's thyroiditis is an autoimmune disorder. When you have Hashimoto's, your body produces antibodies that attack the thyroid. This attack causes it to slow down and impairs the gland's ability to make the essential thyroid hormones your body needs for energy and metabolism.

Other causes of hypothyroidism include:

  • Iodine deficiency.
  • Major hormonal shifts like pregnancy.
  • Problems with the pituitary or hypothalamus.
  • Radioactive iodine treatment to the thyroid gland.
  • Thyroid surgery to remove all or part of the gland to treat thyroid cancer or nodules.

Understanding the root cause of your underactive thyroid gland is essential, as it will help you and your health care provider tailor your treatment.

What is thyroid hormone replacement?

Your thyroid gland produces two essential hormones: thyroxine (T4) and triiodothyronine (T3). A healthy thyroid gland produces sufficient amounts of both T4 and T3. T4 is an inactive or "storage" hormone. T4 is released into circulation and, to be usable, must be converted by the body into the active T3 hormone.

When you are hypothyroid, your body isn't producing enough thyroid hormone. Thyroid hormone replacement treats hypothyroidism by providing medication that gives you the essential thyroid hormone your body needs.

Thyroid hormone replacement drugs can provide forms of T4, T3, or a combination of both hormones. Typically, however, treatment for hypothyroidism starts with T4-only formulations, based on the assumption that the body will successfully convert T4 into T3 on its own.  

Types of thyroid medications: T4, T3, NDT, compounded

Levothyroxine/T4 medications

Levothyroxine is a synthetic form of thyroxine (T4). In some patients, a T4 drug alone can successfully treat the symptoms of hypothyroidism.

Levothyroxine is available as a generic drug and several brand-name medications. The current branded forms of levothyroxine are SynthroidLevoxylUnithroid, and Euthyrox tablets, and Tirosint gel capsules and Tirosint-SOL oral solution.

A different manufacturer makes each generic and brand-name levothyroxine. FDA regulations state that each company's product can vary from 95 to 105% of the stated potency. Hypothyroidism treatment has what's known as a narrow therapeutic range meaning that even slight variations in the potency of thyroid medication can affect your treatment and thyroid levels. Because of these potency differences, your physician may recommend you consistently take only one brand name levothyroxine to treat your hypothyroidism. This prevents you from experiencing unwanted fluctuations in the potency of your treatment from refill to refill, getting medication from different levothyroxine manufacturers.

Because pharmacies and health insurers often automatically substitute a generic for a brand-name medication, be aware that you can ask your doctor to write a "dispense as written" (DAW) or "no substitutions" prescription. This prevents pharmacy substitution and ensures that you consistently receive the brand-name medication.


Euthyrox, made by Merck, is the first levothyroxine tablet available in blister packs. Because blister packs protect against light, heat, and moisture, this improves the stability of the potency. 


Levoxyl is a brand-name levothyroxine drug made by Prizer. Levoxyl is gluten- and lactose-free. Some patients find this medication more comfortable to take because of its gentler rate of absorption. 


Synthroid is one of the most commonly prescribed medicines in the United States, with tens of millions of prescriptions per month. It's made by AbbVie. 


Unithroid is a brand-name levothyroxine drug from Lannett. It is frequently the least expensive brand-name form of the medication. Most commercially-insured patients only pay $3 for a 30-day prescription at most pharmacies.

Tirosint and Tirosint-SOL

Tirosint is a unique brand-name form of levothyroxine made by IBSA. The medication is a liquid and comes in a gel capsule packaged in a blister pack. Tirosint-SOL is the liquid form and comes in individual-dose ampules. Tirosint and Tirosint-SOL are known for more rapid and improved absorption, especially in people with gastrointestinal issues, ulcers, and people who eat or drink coffee when taking their thyroid medication. 

Liothyronine/T3 medications

If your body has difficulty converting T4 to T3, levothyroxine alone may not be enough. For patients who do not feel completely normal taking a synthetic T4 alone, adding T3 may help optimize thyroid levels and relieve hypothyroidism symptoms. 


Liothyronine is the generic name of a synthetic form of the T3 hormone. T3 is the active thyroid hormone that works at the cellular level to help deliver oxygen and energy to cells, tissues, and glands throughout the body. It is uncommon for a hypothyroidism patient to be prescribed T3-only treatment without T4; typically, liothyronine is used in combination with T4.


Cytomel is the most commonly available brand-name version of liothyronine. It is short-acting, only staying active in the body for about 8 hours. Hence, doctors frequently recommend dosing twice a day.

Natural desiccated thyroid (NDT)

Natural desiccated thyroid (NDT) is also known as natural thyroid, porcine thyroid, or desiccated thyroid extract. NDT is made from the dried thyroid gland of pigs and includes natural forms of both T4 and T3 hormones. It's the oldest form of thyroid hormone replacement and has been used since the late 1800s. Because NDT was already in use decades before the creation of the FDA, NDT is not FDA-approved, though the FDA still regulates it.

Some patients and practitioners find that NDT is a preferred hypothyroidism treatment after unsuccessfully trying to optimize thyroid function on levothyroxine or a combination of levothyroxine and liothyronine.

Armour Thyroid

Armour Thyroid is the best-known brand-name NDT drug. It's made by Allergan Pharmaceuticals, a division of AbbVie. 

NP Thyroid 

NP Thyroid, manufactured by Acella, is another T4/T3 combination medication.

Nature-Throid, WP Thyroid, Westhroid

Nature-Throid, WP Thyroid, and Westhroid are natural desiccated thyroid drugs made by RLC Labs. WP Thyroid is particularly notable because it's hypoallergenic and includes only a small number of all-natural fillers. 

Compounded thyroid medication

Compounded medication is a custom-made medication mixed and prepared specifically for you by a compounding pharmacy based on a prescription written by your physician. Because a pharmaceutical company does not make them, compounded drugs don't have "brand names."

Thyroid medication can be compounded using levothyroxine, liothyronine, and natural desiccated thyroid, in any combination and dosage. If you and your doctor decide that compounded medication is the best option for you, make sure that the Pharmacy Compounding Accreditation Board accredits the compounding pharmacy. These pharmacies must go through an extensive process to fully comply with the specified standards. This accreditation establishes that the pharmacy meets a high standard. 

Compounding thyroid medication most commonly comes in capsule form. In addition to the active medications, the capsule will usually include additional fillers. Common fillers used in compounding include lactose, acidophilus, calcium carbonate, mannitol, starch, tapioca powder, sodium bicarbonate, silica gel, hydroxypropyl methylcellulose, and Avicel (microcrystalline cellulose). Talk to your compounding pharmacy about the fillers they use, and ensure that you are not sensitive to any fillers in your medication.

Compounded thyroid medications are not considered FDA-approved because each prescription can be unique. Also, compounded thyroid medications are usually more costly than generic and brand-name thyroid drugs and often not covered by insurance.

What's in your thyroid medication: fillers and inactive ingredients

Thyroid medications, like all medications, often include supplementary, non-medicinal ingredients known as fillers or excipients. These inactive ingredients are separate from the active pharmaceutical ingredient, or API. While these fillers can influence your body's absorption of drugs, inactive ingredients and fillers help ensure that a drug has consistent and reproducible quality. Inactive ingredients and fillers include coatings, lubricants, fillers or diluents, preservatives, coloring agents, sweeteners, flavoring agents, and dyes to add color to tablets.

‍Both active and inactive ingredients in drugs can cause adverse reactions or allergies. If you have allergies or food sensitivities, it is crucial to mention them to your thyroid doctor so that they can prescribe a thyroid medication accordingly.

The following charts summarize the inactive ingredients and excipients in various thyroid medications.

Is there gluten in your thyroid medication?

Medications are not required to label whether they contain gluten. But the following thyroid medications are certified as gluten-free by their manufacturers:

  • Unithroid
  • Nature-Throid
  • Tirosint
  • Tirosint-SOL
  • WP Thyroid

Other thyroid medications that are identified as gluten-free but not certified gluten-free include:

  • Levoxyl
  • Synthroid
  • Mylan-manufactured generic levothyroxine

Note: Starch or sodium starch glycolates are a common filler in thyroid medications that may also contain gluten. For more information on fillers and excipients, read "Is Your Thyroid Medication Gluten-Free?"

What are the side effects of thyroid hormone replacement drugs?

When taken at the right dose, thyroid hormone replacement drugs typically don't have side effects.

The most common side effects of thyroid hormone replacement drugs are due to overmedication—you're taking too much thyroid hormone and experience symptoms of hyperthyroidism.

The symptoms of overmedication may include: 

  • A fast heartbeat, heart palpitations
  • Difficulty sleeping, insomnia
  • Dull, lifeless, or brittle hair
  • Heat sensitivity
  • Hunger
  • Nervousness or anxiety
  • Shakiness
  • Sweating
  • Tiredness
  • Weight loss
  • Diarrhea

Talk to your doctor if you experience any of these side effects. A blood test will help you evaluate your thyroid hormone levels and determine if you are overmedicated.

‍‍Get medical help immediately if you experience any of these rare but severe effects of significant overmedication: chest pain, a rapid heart rate, an irregular heart rate or noticeable heart palpitations, swelling of your hands, feet, or ankles, or seizures.

There's always a small risk that you might have a severe allergic reaction to the fillers, coatings, or dyes in your thyroid medication. If you have difficulty breathing or other signs of a severe allergic reaction after taking thyroid medication, call 911 or go to an emergency room immediately. 

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FDA regulation of thyroid hormone replacement drugs

All standard pharmaceutical products are evaluated to make sure that they work. The FDA's role is to be "responsible for protecting the public health by ensuring the safety, efficacy, and security of human and veterinary drugs, biological products, and medical devices." The FDA does not do independent testing but uses a review process that relies on the research and testing of the manufacturer who submits the approval request.

A prescription drug on the market without FDA approval is still legal to prescribe and is regulated by the FDA. It's also not necessarily harmful and may be effective. All it means to be "unapproved" is that the drug has not gone through the FDA's formal approval process. While unapproved medications are allowed to be prescribed, they are typically not covered by insurance. 

‍Regarding drugs to treat hypothyroidism, levothyroxine (synthetic T4) and liothyronine (synthetic T3) are FDA-approved drugs. Natural desiccated thyroid (NDT) drugs are FDA-regulated but not approved. (NDT drugs were being prescribed decades before the creation of the FDA.) Compounded drugs are also legal to prescribe but not FDA-approved.

Which thyroid hormone replacement medication is right for you?

There are different formulations of thyroid hormone replacement medication. While considering the benefits and differences of your options, it's important to remember that there is no one-size-fits-all solution. Everyone responds differently to different combinations, brands, and dosages. Ultimately, the right thyroid hormone replacement medication for you is the one that works safely and best for you!

While optimal thyroid treatment can require trial and error, here are some pros and cons of each type of medication to help you weigh your options.

Levothyroxine/T4-Only: Pros & Cons

Pros: Taking only a levothyroxine drug is FDA-approved and is typically the least expensive form of thyroid treatment. You typically only have to take one daily dose.

Cons: When you only take levothyroxine, you rely on your body to effectively convert the T4 to the active thyroid hormone, T3. A significant percentage of hypothyroid patients have physical or nutritional issues that impair this T4-to-T3 conversion. T4-only treatment may not be optimal for those patients and may leave them symptomatic.


Levothyroxine + Liothyronine (T4 + T3): Pros & Cons

Pros: Combining levothyroxine and liothyronine increases levels of the active thyroid hormone T3 and can help optimize treatment in those patients with hypothyroidism who don't convert T4 to T3 well.

Cons: This treatment requires at least two daily pills and is most costly than levothyroxine alone. Dosing T3 can also be more complicated for doctors not experienced in prescribing liothyronine.

Natural desiccated thyroid: Pros & Cons

Pros: NDT has been used to treat hypothyroidism for more than 100 years, and some patients who have tried synthetic drugs find that NDT offers the best relief of symptoms.

Cons: Because the FDA does not formally approve NDT, it's often not covered by health insurance. NDT is also sometimes more expensive than levothyroxine. For some patients, the amount of T3 in NDT can sometimes be overstimulating, making it necessary to take smaller doses throughout the day.

We are all unique with individual sensitivities. Our bodies will not all react the same way to a specific medication or dosage. Finding the right thyroid treatment can be complicated. Work with a trusted and experienced team to make sure that the process of treating your hypothyroidism is straightforward and personalized.

How should you take your thyroid medication?

Aim to take your pill at the same time every day. Make it part of your daily routine – i.e., take your medicine before brushing your teeth or combing your hair. This consistency is even more critical when your thyroid treatment includes liothyronine or natural desiccated thyroid because thyroid medications that include T3 are shorter-acting in the body.

If you tend to forget to take your daily thyroid medication, set the alarm to remind you to take your medication. Keep your medicines in a prominent place like your bedside table and make them part of your daily routine.

You should take your pill on an empty stomach. The absorption of thyroid medication is decreased when taking the hormone on a full stomach.

You can swallow your thyroid medication with water or any liquid other than soy milk, milk, grapefruit juice, or coffee.

The following chart summarizes the foods, drinks, and supplements that interfere with the absorption of your thyroid medication. Familiarize yourself with this list and the best timing to ensure you're getting the most out of your thyroid treatment. For more detailed information, read "How And When To Take Your Thyroid Medication."

You should also avoid taking thyroid hormone replacement drugs simultaneously as other medications like statins, blood pressure drugs, and metformin. Your thyroid medication should be taken on its own. If you take other medications, consider adjusting the timing. Take them at least four hours apart from your thyroid medication.

Are there any interactions with thyroid hormone replacement drugs?

Calcium or iron supplements, antacids containing calcium or aluminum hydroxide, and other medications may prevent your body from fully absorbing the synthetic thyroxine. Talk to your doctor to learn how long you should wait to take those other supplements and medicines after administering your daily thyroid medicine.

What should you do if you miss a dose?

You should take your medication as prescribed at the same time of day. However, life happens! Sometimes you miss taking your pill for a day or two. Missing several doses should not dramatically affect your thyroid health, but medication should be re-started as soon as possible.

Taking several doses of levothyroxine is safe to make up for missed doses. However, doctors do not recommend you take catch-up doses of liothyronine (T3), natural desiccated thyroid, or a compounded drug that includes T3.

If you have questions about missed doses, contact your doctor about how to get your thyroid hormone replacement back on track.

What should you know about changing your thyroid medication?

Ideally, once you've optimized your thyroid treatment and your symptoms are under control, you should continue taking the brand or manufacturer of thyroid medication that's working for you. Because each manufacturer's thyroid medication will consistently fall within the 95 to 105% potency range, staying with one manufacturer ensures that you get consistent treatment—as long as your refills come from the same manufacturer.

When changing from one manufacturer to another, or one generic levothyroxine to another, you can experience potency variation that may negatively affect your thyroid function. When switching medications, it's important to retest your thyroid every four to six weeks and adjust your dosage as needed until your levels are stable.

Should you stop taking your thyroid medication?

Suppose you have had your thyroid gland removed surgically, radioactively ablated, or it's not working due to autoimmune destruction from Hashimoto's. In that case, you need to remember that thyroid hormone is essential. You can't live without it.

You should never stop taking your thyroid medication unless your doctor explicitly recommends it. Untreated thyroid disease puts you at risk of worsening hypothyroidism symptoms. It could lead to a variety of health complications, including:

  • ‍Blood pressure irregularities
  • Elevated cholesterol (or treatment-resistant high cholesterol)
  • Low body temperature or feeling perpetually cold
  • Fatigue, muscle weakness, or joint pain
  • Heart problems
  • Depression
  • Memory problems
  • Weight gain
  • Infertility, miscarriage, stillbirth, or premature labor
  • Menstrual irregularities
  • Loss or reduction of sex drive
  • Constipation
  • Hair loss
  • Swollen hands, feet, and face
  • Growth of thyroid nodules or increased goiter size
  • Increased risk of infection

‍Some people with hypothyroidism want to stop taking their medication for various reasons:

You don't feel better taking medication or have new or worsening symptoms. 

Discuss your concerns with your doctor if you're tempted to stop your medication. It may take a month or two to notice a difference in how you feel. If you still don't notice any improvements, get your thyroid levels checked again. You also may need a dosage adjustment, a different thyroid medication, or additional lifestyle changes to complement your medical treatment.

You don't like to take "medications." 

Remember that thyroid hormone replacement is replacing a hormone your body is missing. Synthetic T4 and T3 are bioidentical to human thyroid hormones and function in the body like your own hormone. Much like a type 1 diabetic requires insulin treatment to survive, most people with hypothyroidism require thyroid hormone treatment.

You prefer to use natural remedies. 

No over-the-counter remedy, natural product, or herbal supplement can replace thyroid hormone for hypothyroidism. However, natural, herbal, and nutritional approaches can complement your hypothyroidism treatment. Talk to your healthcare provider about complementary strategies to help your hypothyroidism and support your thyroid health.

You don't have health insurance. 

It can be hard to get treatment for hypothyroidism when you don't have affordable health care or medical insurance. Find out more about managing hypothyroidism without insurance in this article.

You're worried about the cost of medication. 

The price of drugs can make it hard to fill prescriptions. However, there are many ways to save on your thyroid drugs, which are discussed in this in-depth article, "Saving Money on Your Thyroid Drugs."

How should you store your thyroid medication?

Thyroid medications are sensitive to heat, moisture, and humidity. Ideally, you should store your thyroid drugs in a cool, dark place – avoid the bathroom and kitchen!

Guidelines specifically recommend that your thyroid medication be stored at a temperate of 68–77°F (20–25°C) and protected from light and moisture. 

Most thyroid tablets can lose potency when exposed to excessive heat. Some tips:

  • Don't leave a prescription in your car on a hot day.
  • Avoid getting prescriptions by mail if your medication could end up sitting in a hot mailbox for hours.

Individual-dose Tirosint-SOL liquid in plastic ampules and thyroid medications packaged in blister packs – like Tirosint gel capsules and Euthyrox tablets – are more resistant to the effects of heat, moisture, and light.

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‍A note from Paloma Health

Optimizing your thyroid levels with medication is usually the first step in feeling better with hypothyroidism. When choosing thyroid medication, remember that there is no one-size-fits-all treatment. Finding the right medication and optimizing that treatment may require adjustment and patience!

While there is a lot to consider when you are diagnosed with hypothyroidism, taking your medication should not be overwhelming. Once you establish a routine, it will soon become a regular part of your day that it fades into the background.

If you're looking to partner with a top thyroid doctor for your hypothyroidism care, schedule a consultation with a Paloma doctor today. Paloma's thyroid doctors only treat hypothyroidism and focus on helping you feel your best, recommending the best possible treatments based on your symptoms and history. They'll work closely with you to ensure that you enjoy the good health that comes with optimal thyroid function.

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Mary Shomon

Patient Advocate

Mary Shomon is an internationally-recognized writer, award-winning patient advocate, health coach, and activist, and the New York Times bestselling author of 15 books on health and wellness, including the Thyroid Diet Revolution and Living Well With Hypothyroidism. On social media, Mary empowers and informs a community of more than a quarter million patients who have thyroid and hormonal health challenges.

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