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Your Guide to Thyroid Medication

Everything you need to know about thyroid medication for hypothyroidism.
Your Guide to Thyroid Medication
Medically Reviewed by:
Kimberly Langdon M.D.
Medically Reviewed by:

In this article:

  • What is hypothyroidism?
  • FDA regulation
  • T4-only formulations
  • T3-only formulations
  • T4/T3 combination therapies
  • Fillers in thyroid medication
  • Which medication is right for you?
  • How to take medication


What is hypothyroidism?


The thyroid is the butterfly-shaped gland at the base of your neck. It produces hormones that regulate your body's energy use, along with many other essential functions. As part of the endocrine system, the thyroid gland makes and stores hormones that help regulate the body's metabolism in the form of blood pressure, blood temperature, and heart rate. 

When your thyroid hormone production drops, your body processes slow down and change. Hypothyroidism can affect many different systems in your body. Common symptoms of hypothyroidism include cold intolerance, weight gain, dry skin, fatigue, sluggishness, depression, constipation, slowed heart rate, 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 where the body produces antibodies that attack the thyroid. This attack causes it to slow down and decrease the production of the essential hormones your body needs for energy and metabolism.


Other causes of hypothyroidism may be iodine deficiency, major hormonal shifts like pregnancy, problems with the pituitary or hypothalamus, or radiation to the thyroid gland.


Understanding the root cause of your under-active thyroid gland is essential, as it will help you and your doctor tailor your treatment.


FDA Regulation


There are many different formulations of thyroid hormone replacement medication. While exploring the benefits and differences between these many options, it's important to remember that there is no one-size-fits-all option. We are all unique with individual sensitivities. Our bodies will not all react the same way to a specific medication or dosage.


All standard pharmaceutical products are evaluated to make sure that they actually 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 rather, uses a review process that relies on the research and testing of the manufacturer who submits the approval request.


FDA approval means that a drug's benefits conceivably outweigh the risks. A drug without FDA approval is not necessarily harmful; and while these unapproved drugs are sometimes still allowed to be sold, they are typically not covered by insurance. 

Thyroid Medications FDA approved/Not approved


Work with your doctor to determine the best treatment plan for your specific needs, including medication, nutrition, and lifestyle modifications.

T4-Only Formulations


The thyroid gland produces two hormones: thyroxine (T4) and triiodothyronine (T3). Similarly, thyroid replacement medication also comes in T4 and T3 formulations. In a healthy thyroid gland, the inactive T4 hormone is released into circulation and then converted by the body into the active T3 hormone. Often, treatment for thyroid replacement starts with T4-only formulations, assuming that the body can successfully do the conversion on its own. 



Levothyroxine is a synthetic form of T4 which fully replaces the thyroid gland and successfully treat the symptoms of hypothyroidism in most patients.


Your physician may specify a brand name to treat your thyroid condition because the potency of generic thyroxine has a history of varying considerably. These variations come from the many manufacturers and formulations used by different companies. The current branded forms of synthetic T4 are Synthroid, Levoxyl, Unithroid, Tirosint. You may want to ask your pharmacist which manufacturer makes your medicine so you can educate yourself about what you are taking. 


*Fillers in levothyroxine include gluten, lactose, cornstarch, sucrose, and dyes. Some medication don't contain these fillers. If you have allergies or food sensitivities it is important to mention it to your thyroid doctor so that he can prescribe a thyroid medication accordingly.

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As of 2019, Synthroid is the most commonly prescribed medicine in the United States, with tens of millions of prescriptions per month.

While both generic and brand-name T4 formulations are useful, each formulation is absorbed by the body slightly differently for the reasons mentioned above. If you switch from generic to brand-name or vice versa, check your thyroid levels to make sure you are getting the right dose to maintain healthy thyroid function.


*Fillers in Synthroid include lactose, cornstarch, and dyes.


Levoxyl is another brand-name formulation of generic levothyroxine. Levoxyl uses different types of binders and is gluten- and lactose-free. Some patients find this medication more comfortable to take because of a gentler rate of absorption. 


*Levoxyl include dyes.


Unithroid is another brand-name formulation of generic levothyroxine. Unithroid contains no ingredients made from a gluten-containing grain like wheat, barley, or rye. Most commercially insured patients only pay $3 for a 30-day prescription at most pharmacies.

*Fillers include lactose, cornstarch, and dyes.



Tirosint is yet another brand-name formulation of generic levothyroxine. It comes in a gel capsule instead of a tablet, which may help with faster absorption. 


*There are no fillers in Tirosint.


Euthyrox is the first generic levothyroxine sodium available in blister packs, which ensures stability of the medication for the longest time. Euthyrox does not contain dyes, lactose, or gluten.

*Fillers in Euthyrox include cornstarch.


Other T4 Formulations

Other forms of levothyroxine include Unithroid, Levo-T, and compounded T4. Compounded medication is personalized medication in which drug ingredients are combined, mixed, or altered to solve for specific patient needs. Compounded T4 often includes cornstarch. The Food and Drug Administration (FDA) approves all commercially available T4 medication, except compounded T4. 


*Fillers in Unithroid include lactose, cornstarch, and dyes.


Find out which Paloma thyroid doctor is right for you:

T3-Only Formulations


If your body has a hard time converting T4 to T3, or you take an interfering medication, standard T4 medicines may not be sufficient for you. For the few patients who do not feel completely normal taking a synthetic preparation of T4 alone, the addition of T3 may be of benefit. 



Liothyronine is the generic formulation of thyroid hormone, T3. T3 is the active thyroid hormone that works at the cellular level to help with the delivery of oxygen and energy to cells, tissues, and glands throughout the body. It is unusual that someone is prescribed T3-only medication without T4. Typically, liothyronine is used in combination with T4.


*Fillers in liothyronine include cornstarch.



Cytomel is the most commonly available brand-name version of liothyronine. It is short-acting, only staying active in the body for about 10 hours, so it is best dosed twice a day. Symptoms may appear again when the medication wears off. 


*Fillers in Cytomel include gluten, cornstarch, and sucrose.


Other T3 Formulations

Like T4, compounded T3 is an option for those who are sensitive to fillers or don't respond to available T3 formulations. Compounded T3 often contains cornstarch. Work with your doctor to determine the best treatment for you. If you decide that compounded medication is the best option, make sure that the pharmacy is accredited by the Pharmacy Compounding Accreditation Board. These pharmacies must go through an extensive process to achieve full compliance with the specified standards, and this accreditation proves to physicians and patients that their pharmacy meets a very high standard. 

T4/T3 Combination Therapies


Those who are interested in a more natural approach may prefer combination therapies. There are two main types of combination thyroid medications - desiccated and compounded.

Like compounded T3, compounded T4/T3 is custom-made in specializing compounding pharmacies to provide the strength and T4:T3 ratio that a patient needs. It gives the most flexibility for those who need a precise dosage.



Armour is the most common T4/T3 combination treatment. It is a brand-name of natural desiccated thyroid. Natural desiccated thyroid (NDT) is derived from the dried (desiccated) thyroid glands of pigs and provides T3, T4, and other thyroid hormones found in the human thyroid. Pigs produce T4 to T3 at a 4:1 ratio, which is higher than the human proportion of 14:1.


Desiccated animal thyroid was the most common form of thyroid therapy before the individual active thyroid hormones were discovered. Because there is no evidence that NDT has any advantage over synthetic T4, it is not currently FDA-approved and is prescribed less frequently today. Some patients love Armour Thyroid, while others feel better with an alternate option. As always, it's important to work with your doctor to find the right treatment for you.


*Fillers in Armour include cornstarch.



Nature-Throid is another T4/T3 combination medication also made of desiccated pig thyroid but uses different binders and fillers, which affects how different people absorb the medicine. 


*Fillers in Nature-Throid include lactose.


NP Thyroid 

NP Thyroid, manufactured by Acella, is another T4/T3 combination medication. It is gluten-free, dye-free, and dissolves under the tongue, which may be helpful to those who have difficulty swallowing pills.


*There are no fillers in NP Thyroid. 


Non-active Ingredients


Thyroid medications, like all medications, often include supplementary, non-medicinal ingredients commonly known as fillers. These inactive ingredients are the part of the product that do not increase or affect the medicinal properties of the active ingredient. While these fillers can influence your body's absorption of drugs, these non-active ingredients help to ensure that a drug has consistent and reproducible quality.

Non-active elements may include coatings, lubricants, fillers or diluents, preservatives, coloring agents, sweeteners, or flavoring agents. Common fillers for tablets and capsules include cornstarch or sugars like glucose and sucrose. In liquid formulations, glycerine and water are used to dissolve or suspend active ingredients.

Both active and inactive ingredients can cause adverse reactions or allergies. It's important to know which fillers are in the medication you take so that you can avoid possible reactions like rash, bloating/diarrhea, or headaches.

Side Effects


If taken at the right dose, thyroid replacement therapies should not cause side effects. Side effects may be an indication that you are taking too much thyroid hormone.

These side effects may include: 

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

Talk to your doctor if you experience any of these side effects. A blood test will help you check and understand your thyroid hormone levels.

Which medication is right for you?


As you see, with possible overwhelm, many possible medication options can tailor to your specific needs. While there are no perfect formulations, medication can undoubtedly help optimize thyroid function.


Perhaps looking at some of the pros and cons of each type of medication can help you weigh your options.


T4-Only: Pros & Cons

Pros are that this type of therapy is FDA approved, least expensive, includes only one pill, and presents the least side effects. Cons are that this type of treatment relies on your body to convert to T3 and contains many fillers and dyes.


T4 + T3: Pros & Cons

The pros are that this type of therapy increase T3 levels for those with reduced T4 to T3 conversion. The cons are that this type of therapy requires two pills, includes many fillers and dyes, and needs an experienced doctor for dosing.


T4/T3 Combination: Pros & Cons

Pros are that this type of therapy may require only one pill, and it is a more natural approach with less fillers and dyes. Cons are that this type of treatment is expensive, not regulated by the FDA, and has a lower T4:T3 ratio than is needed in humans (thus requiring a possible second pill).


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 is tricky, and you should work with a trustworthy care team to make sure that the process is straightforward and personalized.


How to Take Thyroid Medication


Thyroid hormone replacement drugs are powerful, so it's critical to be under careful medical supervision when on these drugs, especially when starting a new brand or increasing dosage.


If you have subclinical hypothyroidism, you and your doctor may choose not to use medication to treat. Instead, your care team may recommend dietary and lifestyle changes to maintain your thyroid levels. However, if you experience symptoms, your doctor may suggest medication. 


Tips for Taking Medication 


  • Take your pill at the same time every day. Make it part of your daily routine – i.e., take your medicine before you wash your face or comb your hair. This consistency is more critical for T3-only and T4/T3 combination medications because T4-only medications are longer-acting in the body.
  • Take your pill on an empty stomach. The absorption of levothyroxine in the gut is decreased when taking the hormone at the same time as calcium, iron and some foods and other drugs. Because of this, patients are usually instructed to take levothyroxine on an empty stomach 30-60 minutes before food intake to avoid erratic absorption of the hormone.
  • For patients who may want to add milk to their morning coffee or cereal, there are alternative dosing strategies, including taking levothyroxine at night since milk can reduce levothyroxine concentration.
  • Avoid co-administration with other medications such as statins, blood pressure drugs, and metformin. Levothyroxine should be the only medication taken at bedtime or in the morning . If you must take other medications that must be taken in the evening, consider adjusting the timing of these medications so you take them with dinner, leaving four hours afterward so you can take the levothyroxine at bedtime.
  • Swallow your pill with any liquid other than soy milk, grapefruit juice, or coffee. Most T4 formulations, except Tirosint, can be crushed and dissolved in water for administration. 
  • Learn about interactions. 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 you have administered your daily thyroid medicine.
  • Stick to one brand. While the FDA has deemed the available brands of synthetic thyroxine safe and effective, they are all made a little differently. Each of the brands of medication contains the same active ingredient, but the small differences in the pill makeup could influence the way your body absorbs and uses them.
  • Get medical help right away if any of these rare but serious effects of high thyroid hormone levels occur: chest pain, fast/pounding/irregular heartbeat, swelling hands/ankles/feet, seizures. 

If You Miss a Pill

You should take your medication as prescribed. However, life happens! Sometimes you miss taking your pill for a day or two. Missing a couple of doses should not dramatically affect your thyroid health, but medication should be re-started as soon as possible. However, if you miss more than a few doses, your body will think it is getting a lower amount of hormones and will respond accordingly, and should be discussed with your doctor.

Changing Medication

Brand-name medications are typically consistent, in terms for potency, from refill-to-refill. However, generics have a history of variation, which may have a negative impact on your thyroid function. You can ask your doctor to write a "dispense as written" or "no substitutions" prescription for a brand-name medication.

If you do switch medications, whether brand-name or generic, it's important to retest your thyroid every four to six weeks and adjust your dosage as needed until your levels are stable.

Always try to closely monitor your TSH levels as you are changing medication

Stopping Medication

It is ill-advised to stop taking your thyroid medication without the supervision of a doctor. Untreated thyroid disease puts patients at risk for other health complications and other life threatening situations.

These risks include:

  • Blood pressure irregularities
  • Elevated cholesterol (or treatment-resistant high cholesterol)
  • Low body temperature or feeling perpetually cold
  • Fatigue, muscle weakness, or joint pain
  • 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 reasons that people stop taking their medication, plus solutions:

  • You don't feel better taking medication, or you experience new or worsening symptoms. You should discuss these issues with your doctor. It may take up to a few weeks to notice a difference in how you feel. If you still don't feel better after a four to six week adjustment period, you may need a dosage adjustment or different medication.

  • You prefer to use natural remedies. Again, talk to your doctor. In most cases, there isn't a natural or herbal replacement for thyroid hormone, but your doctor can work with you to discuss nutritional and lifestyle support.

  • You're worried about the cost of medication. It's a smart investment to get affordable health insurance. Find more resources here and here.

  • You can't remember to take your dose. Set an alarm on your phone, computer, or good old fashioned alarm clock as a daily reminder. Keep you medications in an obvious place like your bedside table to bathroom counter and make it part of your routine.

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. 


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, soon it will become such a part of your day that it fades into the background.


Schedule a consultation with a Paloma doctor today. Paloma Thyroid doctors want you to feel your best and will explore all possible treatments based on your symptoms and history. Our doctors only treat hypothyroidism. They'll work closely with you to find the optimal functioning of your thyroid.

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Katie Wilkinson

Katie Wilkinson is the Head of Content and Community at Paloma Health. She is passionate about the intersection of healthcare and technology. Living with an autoimmune condition and having been let down by the traditional healthcare system, Katie has a personal and professional interest in improving patient access to better care.

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