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Episode 6 | Getting Up to Speed on Levothyroxine

A look at the various types of levothyroxine available, their risks and costs, and the impact on your hypothyroidism treatment, featuring pharmaceutical expert and researcher Dr. Charles Carter.


“Medical education has in essence forgotten -- for the general practitioner in particular --that this is a narrow therapeutic index drug. That can make it difficult to get the right dose for the right patient at that point in time for the patient. You think about the strengths this product is available in, it's down to the microgram, and we got multiple strengths, just varying a degree of micrograms from one product to the next. That should in itself tell you that it's a difficult product to optimize the dose, but it's often forgotten. A better understanding by the medical community of their options in terms of formulations of levothyroxine products would be, I think, beneficial clinically and beneficial economically to the health systems, as well as the patient.”

~ Dr. Charles Carter


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MARY SHOMON: Do you want to finally live and feel well with a thyroid condition? Then I want to welcome you to the Thyroid Deep Dive podcast. I’m your host Mary Shomon. It’s time to dive in!

You can’t talk about hypothyroidism without talking about levothyroxine, the drug that’s a synthetic version of thyroxine – the T4 thyroid hormone. In the U.S., you may know it by brand names like Synthroid, Tirosint, Levoxyl, Unithroid, or Euthyrox.

Conventional physicians consider levothyroxine the primary – and in many cases, the ONLY -- treatment for an underactive thyroid. As a result, levothyroxine is considered the so-called “standard of care” for hypothyroidism. As a result, the majority of thyroid patients end up taking levothyroxine. Many of you listening are probably taking it right now.

But there are some challenges that some of you may not know about, and doctors just don’t discuss. First, many patients are unhappy with their treatment, and studies show that the majority of patients are NOT well-controlled on levothyroxine tablets.

Second, many patients -- and in some cases, their doctors -- are still unfamiliar with or misinformed about levothyroxine options.

Find the right hypothyroidism treatment for you, and you can relieve your symptoms, be happy with your treatment, and control your hypothyroidism well. End up on the wrong medication, and you can continue to have symptoms like fatigue, brain fog, depression, and weight gain – for years, or even a lifetime!

You may think that there’s not much difference between one levothyroxine drug or another, but you couldn’t be more wrong. If there’s one thing I want you to remember, it’s this: All levothyroxine is NOT alike.

There are brand name pills and generics, and they are different. Different fillers, dyes, and coatings. Different pills – even at the same dosage – have different potencies. Then there are liquid gel caps and oral solution levothyroxine. How can you know which one is right for you, especially if you don’t know all your options? That’s why it’s time to get up to speed on levothyroxine.

In this episode, we’ll look at the pros and cons of different types of levothyroxine. You’ll also hear from pharmaceutical researcher and professor, Dr. Charles Carter, about the risks of compounded liquid levothyroxine, and how the costs of levothyroxine treatment. So, let’s dive in and get up to speed on levothyroxine!

Different Types of Levothyroxine

I want to start out by running through the three types of levothyroxine. First, there’s the best known form of levothyroxine – tablets. In the tablet area, you’ll find the brands – including Synthroid, Levoxyl, Unithroid, and Euthyrox. There are also many companies making generic versions of levothyroxine. Second, there are gel capsules, that contain a liquid form of levothyroxine. It’s a brand name, called Tirosint. Finally, there’s a levothyroxine liquid – known as an oral solution, also a brand name -- Tirosint-SOL.


What’s different about the 3 types of levothyroxine? Well, the first thing to keep in mind is something called excipients. The active ingredient in all 3 types of levothyroxine drugs is the levothyroxine – the synthetic thyroid hormone -- itself. Like all medications, levothyroxine also includes excipients. Excipient is the fancy term for the inactive and inert ingredients that serve as fillers, binders, and coatings.

Excipients can affect how well you absorb your levothyroxine.

There are four excipients in particular that you need to be on the lookout for in levothyroxine tablets.

Acacia is a pollen-producing tree/shrub that can trigger sensitivities in the 30% of the public that has seasonal pollen allergies and hay fever. Synthroid, Unithroid, and some generic tablets have acacia.

Lactose is the ingredient in dairy products that can trigger sensitivities in people who are lactose-intolerant. You’ll find lactose in Synthroid, Unithroid, and some generic tablets. FYI, the National Institutes of Health estimates that around 65% of the population has some degree of lactose intolerance.

Then there’s crospovidone, also known as povidone. It’s a form of iodine, and can trigger symptoms in people who are sensitive to iodine. It’s found in Synthroid, and some of the generic tablets.

Finally, there’s glycolate, also known as starch glycolate, which frequently includes wheat starch and gluten. This can cause problems for people with celiac disease, gluten intolerance, or gluten sensitivity. Most of the levothyroxine tablets have some form of glycolate in them. Euthyrox tablets, however, are certified gluten-free.

Overall, about 15% of the population is allergic or sensitive to various excipients in medications. How do you know if you’re one of them? First of all, your thyroid medication may not work, and leave you symptomatic. This is a major warning sign. But some specific signs and symptoms include a skin rash, hives, itching, fatigue, swelling, stomach pain, diarrhea, bloating and gas, and migraine.

If you have any signs or symptoms of sensitivity to excipients, here’s a basic step to take: Talk to your doctor about switching to a specific brand that doesn’t include the most problematic excipients. There’s a detailed chart of the excipients by medication available in a free ebook I’ve put together on levothyroxine. You’ll find it at

And here’s another tip: All the tablet forms contain multiple excipients, and sometimes it’s hard to figure out which one could be causing problems. That’s a good time to consider Tirosint and Tirosint-SOL. Tirosint gel capsules have liquid levothyroxine, and are considered hypoallergenic, with only three excipients: gelatin, glycerin, and water. Sensitivity or allergies to gelatin and glycerin are extremely rare. Tirosint-SOL oral solution levothyroxine has only two excipients: glycerol and water. Sensitivity or allergies to glycerol are also extremely rare.


We also need to talk about dyes in levothyroxine. If you look at most levothyroxine tablets, you’ll notice that they are different colors to go with the different dosage sizes. They get their color from various blue, red, and yellow dyes. So here’s the deal. While the dyes are approved for use in the U.S., they are NOT approved in many other countries. Various watchdog groups have demanded that the FDA ban the use of dyes, due to a long list of potential adverse health effects.

You can avoid any issues with dyes by only taking the 50 mcg size levothyroxine tablets of all brands and generics, which are white, and contain no dyes. Also, here’s some good news. All dosage sizes of Euthyrox, the newest brand of levothyroxine tablets on the U.S. market, are white, and have no dyes.

And, more good news. Tirosint capsules and Tirosint-SOL oral solution contain no dyes whatsoever.

Food, Supplements, Coffee, and Medication

Here’s another issue related to levothyroxine effectiveness. Your absorption of levothyroxine is negatively affected by food, beverages, supplements, and medications -- for example, coffee, milk, high-fiber foods, calcium and iron supplements, antacids, and proton pump inhibitor drugs like Prevacid. To reduce the risk, you need to take levothyroxine on an empty stomach, and wait at least an hour before eating or drinking coffee, and wait 3 to 4 hours before taking calcium or iron supplements, antacids, and drugs like Prevacid. Even then, however, you may still have absorption problems.

Also, if you have any digestive or gastrointestinal conditions that change stomach acids or impair absorption -- like ulcers, irritable bowel disease, Crohn's disease, and celiac disease – here’s some important information: These conditions can interfere with your full absorption of levothyroxine tablets.

One way to bypass these problems. Research has demonstrated that Tirosint and Tirosint-SOL are highly resistant to most effects of foods, drinks, supplements, and medications, resulting in more successful and speedy resolution of hypothyroidism compared to tablets.

Potency Fluctuations

All forms of levothyroxine are required to fall within the FDA-mandated range of 95-105% of stated potency. That means that if you have a levothyroxine that’s a 100 mcg dosage, it can actually range from 95 mcg to 105 mcg in actual potency. Each manufacturer – brand name or generic – has its own potency.

This is a problem if you are taking generic levothyroxine tablets, because with each refill, you can get medication from a different manufacturer. This makes careful control of your hypothyroidism difficult, and can be the reason why you’re still symptomatic, or your thyroid test levels are fluctuating.

If you take a brand name, and stay on the same brand, this isn’t a problem.

If you’re taking a generic levothyroxine, you have two choices: switch to a brand name. Or, you can work with a pharmacy that will ENSURE that you get the same generic manufacturer with every refill. (For mail order levothyroxine without insurance, check out Honeybee online pharmacy. They let you specify the manufacturer for your generic levothyroxine.)

If you are taking most levothyroxine tablets, you also need to make sure that you store your levothyroxine carefully, away from light, moisture, and heat. So, no bathroom, no kitchen, folks! And be careful with mail order during the summer – you don’t want your levothyroxine sitting in a hot mailbox for hours.

One way to ensure potency: both Tirosint brand levothyroxine gel capsules and Euthyrox brand tablets come in individual blister packs, which protect them from light, moisture, and heat damage, and helps maintain potency over time. And Tirosint-SOL oral solution comes in individual-dose ampules that also protect the medication.

Compounded Liquid Levothyroxine

But compounded liquid levothyroxine comes with significant problems and warnings, as I learned from Dr. Charles Carter. Dr. Carter is a clinical and analytical pharmaceutical researcher and investigator on dozens of drug and health economics studies. He’s also an Associate Professor of Clinical Research at Campbell University's College of Pharmacy and Health Sciences. Dr. Carter is lead author on a major study on compounded liquid levothyroxine that was released in late 2020.

MARY SHOMON: I'm aware of a lot of integrative doctors and patients that are getting compounded, T3 medications, and occasionally even getting their levothyroxine or their natural thyroid compounded. But I haven't heard of too many people getting compounded liquid. Is that a thing that's out there that I'm not aware of?

DR. CHARLES CARTER: One of the concerns, if we're treating a patient with hypothyroidism is twofold. We recognize that it's a narrow therapeutic index drug. We recognized that the interval between an effective dosing regimen and the dosing regimen, that's either supra or super therapeutic is quite narrow.

Hence we got that categorization. Same time, environmentally, there's this growth in personalized medicine and compounding pharmacies. And it does create a concern. I do not have the exact number or percentage of patients that are getting compounded levothyroxine, but we do know that it happens, particularly in those patients that are difficult to control or -- and this is the big unknown -- if they're moving from one brand or generic formulation of the traditional levothyroxine to another, they can have significant differences in absorption.

And one of the ways to get around that is actually consistently compounded, especially if the company was coming from the same pharmacy, because there's continuity of care there. Reason that's a problem is because even if it's occurring, likely a very small number of cases, the guidelines for the treatment of hypothyroidism that were published in Thyroid. It literally says that, and I'm especially quoting here, "there are no compounding recipes that produce a stable concentration of levothyroxine in suspension. Efforts to create suspensions should be avoided and can be associated with marked extremes in dosing." As the medical guidelines say, we shouldn't be doing this.

So, in a very strange way, or a very interesting way, a better way of saying it, I do believe that we shouldn't be doing this at all, because the guidelines clearly state we shouldn't be doing it. And yet it's being done.

What we do know is that people that are either hypothyroid and sub-therapeutically treated do not get relief from their symptoms. And if they are supra-therapeutically treated -- just because of increased absorption, food, drug interactions, drug-drug interactions, you name it -- there can be higher levels than what is desired. And a good percentage of them end up in the emergency room.

MARY SHOMON: Before the introduction of Tirosint, in particular, the liquid formulation in the last couple of years, there probably were some situations where patients felt a need to get a compounded suspension, a compounded liquid.

But now that we have a manufactured and very specific and very controlled liquid version of levothyroxine, it sounds to me then that your research is arguing that there is no reason or really no room for compounded liquid levothyroxine.

DR. CHARLES CARTER: I would agree with that. I would say that the risks of compounding levothyroxine that are presented to the patient outweigh the benefits of doing it because now we have essentially a pure form of levothyroxine in the gel caps. And now we have an oral liquid solution that we could then titrate a patient's dose specifically to what they need without going through the whole compounding process and dealing with stability issues. And although we didn't test for it, also sterility issues.

MARY SHOMON: The main reason, if I'm understanding it correctly, that people have turned to compounding in particular, in the area of levothyroxine drugs is that they're trying to get forms of a medication that don't have as many excipients and dyes and coatings.

Because they're reacting to them that are in some of the traditional tablets and such. If that's the primary rationale, at least in the levothyroxine space, for compounding, then both the Tirosint capsules and even more so the Tirosint liquid would really alleviate and eliminate any need for compounded versions of levothyroxine because we have them manufactured under much stricter and much more careful process then can take place in compounding. And, it's essentially the purest cleanest version of what we're talking about. Correct?

DR. CHARLES CARTER: That is correct. It obviates all the risks of compounding.

MARY SHOMON: So when you did this study, I'm looking at the data here and depending on when you checked it -- a couple of days, a week later, two weeks, three weeks, four weeks, around five weeks later -- you were getting all sorts of variation from... how many different compounded products did you look at as part of your study?

DR. CHARLES CARTER: There were a total of 12 products, six of them came from the community and six of them were performed by our students at our college that all already completed their compounding training and had high quality equipment presented to them. And we wanted to look at that group because they're the individuals that have just completed their training, so they were proficient in it. Out of the 12, one of them actually ended up having the wrong product altogether, so we cut that one, and we analyzed 11 of them.

MARY SHOMON: And all of them seem to come back with pretty significant variation in the potency and percentage levels of levothyroxine in them.

DR. CHARLES CARTER: That is correct. And one thing about the study. The way we did it, we tried to mimic real world utilization. So, the concept of what is a suspension becomes critical in understanding this variability, as well as the concept of degradation. The fact that it's a suspension is that when a patient would withdraw from the container, the vial, to take a measured dose by volume, there could have been more or less drug in there. And as a matter of fact, the quality of that compounding in part drives the size of the particles that are actually suspended in the fluid.

I think our study points in this direction as one of the probabilities or reasons for this variation. One is degradation of the product. The other is the fact that the manufacture or the compounding of the product for a particular patient that the particles were various sizes.

So, we'll see the dosage that a patient was getting go down. We'd see it go up. But over the 34 days we did these measurements, literally they got lower and lower and lower, which was reflective of something that was previously reported in the literature—that these compounds just degrade when you manufacture them, when you compound them.

MARY SHOMON: Was there any consideration given in the study also to the accuracy of people drawing up the dose? Because I'm thinking about, when my children were little and trying to get that amoxicillin with the plunger, and am I getting one millimeter to two milligrams? How much am I giving and feeling like I was never really accurate, and it never worked out at the end that I have the exact number of doses I was supposed to have. So obviously I wasn't measuring as tightly as I should. Is that a factor that was taken into consideration in your study?

DR. CHARLES CARTER: We realized that that was a factor in the real world, but when we received the products after compounding, that's in essence where a lot of the real-world aspects of the study stopped, because then the samples went into a laboratory, and they're measured out very precisely.

So, the results that we saw in variability in this study may actually be more compounded when somebody who is caring for our patient or the patient themselves doing this in conditions that are outside of a laboratory. I think that that is a critical element to consider that would, in my opinion, either provide further evidence that the variability will be expanded over time.

MARY SHOMON: So, it's probably fairly safe to assume that the level of variation that you all observed was a best-case scenario under laboratory settings with people using very precise ways of measuring out these doses. Whereas the typical patient using a syringe and pulling up whatever they can and trying to get a fairly accurate measurement, is going to be less precise at best.


MARY SHOMON: The evidence seems quite clear. In almost all cases, compounded liquid levothyroxine needs to be retired. If you’re a patient who needs a low-excipient, liquid form of levothyroxine, you should talk to your health care provider about the Tirosint-SOL oral solution.

Cost Issue

MARY SHOMON: We’ve talked quite a bit about the differences in formulations and ingredients and such, but let’s also discuss another critical issue – cost. The cost of levothyroxine falls into a wide range. You may be able to get generic levothyroxine or a brand like Unithroid through insurance for no copay at all, or just a few dollars a month. Even without insurance, you can get generic levothyroxine at a cash price of typically less than $15 a month. But then, when you get into some of the brand name drugs, like Synthroid, you start to see much higher copays, and uninsured cash prices of $50 or more per month. And because Tirosint capsules and Tirosint-SOL liquid are specialized levothyroxine, some insurance companies charge you a huge copay – sometimes more than $100 a month. And the list price at some pharmacies can run more than $150 a month.

Because generic levothyroxine is so inexpensive, that’s what most patients end up taking. But what you save on the cost of the medication may end up costing you more in the end, as Dr. Carter and I discussed.

From my reading of the research, my understanding was that you looked at all the different factors that take place when someone is put in the category of "difficult to treat" hypothyroid patient, meaning someone who is having recurrent symptoms, their TSH and thyroid levels are not responding as they should appropriately to the intervention, the treatment. And so, their doses are needing to be changed or in some cases, the form of medication that they're getting is changing. So, what you looked at in that study was how much is it costing for these patients to have fairly frequent changes in medication compared to an alternative of being put on a stable brand formulation of thyroid medicine.

And you were looking at when somebody has to change medicine, well, they're going to lose time from work, because they have to go for a doctor visit. They have the cost of a physician visit or a specialist visit. They have the cost of new medications and copays that may be involved in a replacement, prescription. There's even hospitalizations and cardiac issues, visits to the emergency department, lab tests, further imaging. And my reading of your research was that, ultimately, when you looked at all of this from statistical standpoint, that the cost of someone who had more than one dosage change annually was so much greater than if we put them on a slightly more expensive, but more reliable and consistent levothyroxine.

DR. CHARLES CARTER: You hit the nail on the head. That's it exactly.

MARY SHOMON: Why is this such an issue that you had to do research on this? To be pretty frank with you, it sounds like a no brainer to me. Why do we need to have this kind of research to establish something that seems to be fairly obvious?

DR. CHARLES CARTER: It's a really, really good question. And people have asked me this question in the past and the points I'm about to make it should answer that question. Thyroid disease, hypothyroidism in particular, has been around for ages. Levothyroxine is the standard of care. Levothyroxine is a replacement hormone for what the body typically means.

Levothyroxine has gone from branded products to generic products, and there really isn't new treatments coming about to replace levothyroxine. Medical developments and medical advances in new pharmaceutical products are tackling other unmet medical needs.

Probably and in terms of magnitude are greater than what we have because we have this array of levothyroxine products. So therefore, I think medical education has in essence forgotten -- for the general practitioner in particular -- that this is a narrow therapeutic index drug. That can make it difficult to get the right dose for the right patient at that point in time for the patient.

And all of these dynamics come into play. And when you get somebody who's diagnosed, recently diagnosed, or has been diagnosed and treated for some time, but another co-morbidity or another characteristic arises in that patient that this drug needs to be modified...the dosage of it. And even if it's a newly diagnosed patient, you think about the strengths this product is available in, it's down to the microgram, and we got multiple strengths, just varying a degree of micrograms from one product to the next. That should in itself tell you that it's a difficult product to optimize the dose, but it's often forgotten. It's just often forgotten. And up until the point that the Tirosint products became available, we had similar products across the board in terms of tablets and that the formulation of them, albeit they had different excipients and different pharmaceutical characteristics of the tablets.

The bottom line is this is an easy area to forget, but we really shouldn't. It's almost like if I'm talking to a group of endocrinologists, they totally get it. They could give me lectures on this matter. But you're talking to an individual who's not kept abreast of the literature and the developments and the management of hypothyroidism, this could become a forgotten aspect that while the diagnosis is correct, the right drug is being prescribed, with all the various products that we have out there and their unique characteristics, titrating a patient to the proper dose with the other dynamics going on in the patient simultaneously over their course of their lifetime -- it becomes pretty difficult.

Another way of looking at it is that narrow therapeutic index drugs are categorized for a very specific reason. And that categorization is made inside the FDA's. website. You can get a list of narrow therapeutic index drugs, and it's small.

We're not looking at hundreds of different products. We're looking at maybe a dozen or less products. Levothyroxine is one of them. I believe personally, it's an often-forgotten parameter or characteristic about levothyroxine that it is a narrow therapeutic index drug, and that it is difficult to titrate patients.

You multiply that by the fact that there's a lot of people walking around this country with hypothyroidism, the numbers, the dollar expenditure, or the inefficiency of not getting somebody on an appropriate tolerable dose can become very costly and that's kind of what our study shows.

MARY SHOMON: Interesting. I definitely would agree with you because it does seem that hypothyroidism is so ubiquitous and the availability of cheap generic $5 prescriptions for levothyroxine are so easy that doctors, they're thinking in the short term, in some cases, rather than the longer term.

More like, "Well, let me just put somebody on generic levothyroxine and then we'll see how they do.” And then, once you've gotten to the point where you've had to have two or three dosage changes, or even a patient that says, "Look, this isn't working. I want to try a brand, or I want to switch brands," you're already in for a fair amount of time and money, in the manipulation and changes and modifications to these doses.

The other issue that seems to come up for me is you said, endocrinologists understand this completely, but they're not the ones that are treating the majority of thyroid patients out there. We have only a couple thousand endocrinologists in the United States. The vast majority of people with hypothyroidism are being diagnosed by their GPS, their primary care, their gynecologists their various doctors that they're seeing that are not thyroid specialists.

And I'm guessing that those doctors are going to be less up to speed on these issues of the narrow therapeutic index and the availability of some of these options that may be better able to give them control and response in their patients.

That's essentially why the economic analysis showed the results that it did in my mind, because that was exactly what was happening.

DR. CHARLES CARTER: So I agree with you a hundred percent.

MARY SHOMON: We know, for example, with Tirosint, that it's strongly recommended for patients who have Crohn's disease or celiac or other sorts of malabsorption issues. Some of the endocrinologists I've talked to have said, "Well, right out of the gate, if I know that a patient has that sort of an issue or an absorption problem, I'm going to tell them their best choice is going to be Tirosint. Now they may not want to do that, or they may choose a different drug, but that's usually what I'm going to recommend to them to start out with."

But I can tell you any of the other doctors that I've talked with, Tirosint ends up being a last resort levothyroxine for them rather than a first choice. And it sounds like it's a function of awareness more than anything.

DR. CHARLES CARTER: Correct? I would agree with that. A better understanding by the medical community of their options in terms of formulations of levothyroxine products would be, I think, beneficial clinically and beneficial economically to the health systems, as well as the patient.

MARY SHOMON: What could be done to get this information in front of the doctors that are prescribing, because obviously a company like IBSA doesn't have armies of drug reps, like an AbbVie or a Pfizer that are hit ting doctor's offices day and night. And they're a small company. It's more of a specialty product . How do they get in front of these doctors? How does the word get out to these doctors or is it really, an uphill battle?

DR. CHARLES CARTER: Awareness is one thing. And then, solid education is another. Presentation of the results on the study we talked about first at the American Thyroid Association was impactful.

Getting the word out through channels of communication, just like this podcast, would be effective. Also addressing the gatekeepers -- and by gatekeepers I'm talking about the individuals like third party payers, pharmacy benefit managers -- understanding that you've got to look at the totality of the costs of the patient.

The challenge of getting that is a challenge for a company that's bringing this product in, trying to increase awareness because the increased awareness is probably going to increase utilization and perhaps, a more beneficial, more timely, therapeutic benefit to the patient.

It's gonna change. Let's think about this for a second. Levothyroxine's been around for ages. Getting the word out that there is a branded form of levothyroxine in a unique formulation that may obviate the challenges of the tablet formulations is going to take time, but it needs to be persistent. In fact, some of the ways that the patients become more aware of it, they can drive the payers in our medical community to be aware of it. And then our prescribers need to be aware of it.

MARY SHOMON: Really, it needs to be coming from all directions top down and bottom up from the patients up to their prescribers and to their insurers and the PBMs. And the doctors also need to be more aware of it. One of the challenges that I've run into in talking with some of the different doctors and patients is also doctors that are really confused about the cost of the drug. And they will say to me, "Oh, well, it's a great drug, but nobody can afford it. It's way too expensive." And I'll say, "Well, have you heard about their programs so that you can get it for $25 a month if you're insured or $40 a month if you're paying a cash price and that's consistent with Synthroid. So, it doesn't really price it outside the realm of possibility for the majority of your patients."

And they're like, "Whoa! I didn't know about that!" It's news to them. So, I think sometimes their patients are self-selecting themselves out of the possibility and doctors are not even offering the opportunity because they've decided ahead of time that it's too expensive, but they don't realize that it may not be the case.

DR. CHARLES CARTER: I totally agree with that completely. As long as the message is getting to the patients and the patients are guided the right way, I think that we would see an overall improvement in the numbers of patients that actually would benefit from a drug like Tirosint.


MARY SHOMON: If you are starting levothyroxine treatment for hypothyroidism – or your levothyroxine isn’t working the way you need it to -- make sure that you take into consideration all the key factors that could be having an impact.

  • Do you have allergies or sensitivities to any of the ingredients used as excipients?

  • Do you have allergies or sensitivities to dyes?

  • Do you have any pre-existing digestive or gastrointestinal conditions that negatively affect absorption?

  • Are you storing your levothyroxine properly to protect potency?

This is also a good time for me to again mention my Levothyroxine Deep Dive program. It’s a completely free educational program that includes educational video webinars, and a downloadable book, and it goes through everything you need to know about brand name and generic levothyroxine, including information discussed in this podcast about the excipients, dyes, absorption, and all the various savings programs for your medication. I would love for every thyroid patient who is prescribed levothyroxine to take advantage of this free educational program. You’ll find it at and there’s also a link in the show notes.

I want to thank my guest, Dr. Charles Carter, for sharing his fascinating research findings and guidance on levothyroxine. You’ll find links to Dr. Carter’s journal studies, the hypothyroidism treatment guidelines he referenced, and other helpful resources and links – along with a full written transcript of this episode -- at the Thyroid Deep Dive website,

And remember that every episode of the Thyroid Deep Dive podcast has the same goal: to provide you with practical information that will help you enjoy the very best health possible. You can subscribe and listen at all your favorite podcast platforms.

This is Mary Shomon, and I want to thank you for listening to the Thyroid Deep Dive. Today, and every day, may you feel well and live well.


Resources and Links

Free “Levothyroxine Deep Dive” Educational Program -- Free Webinars and Book

Charles A. Carter, BS, PharmD, MBA

Associate Professor of Clinical Research, Campbell University's College of Pharmacy and Health Sciences

Stability and consistency of compounded oral liquid levothyroxine formulations, Journal of the American Pharmaceutical Association

The Economic Impact of Changing Levothyroxine Formulations in Difficult-to-Treat Hypothyroid Patients: An Evidence-Based Model, Pharmacoeconomics (PDF)

Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement, Thyroid



The Levothyroxine Deep Dive is a free, comprehensive educational program that covers everything you need to know about levothyroxine treatment for hypothyroidism, including information about Synthroid, Levoxyl, and Unithroid tablets, Tirosint capsules, Tirosint-SOL oral solution, and generic levothyroxine tablets. The program includes an online guide, a multi-part video webinar, and a downloadable book, available at no cost. See to access the program at no cost.

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The Natural Thyroid Guide is a free, comprehensive educational program that covers everything you need to know about natural desiccated thyroid (NDT) treatment for hypothyroidism, including information about Armour Thyroid, Nature-throid, WP Thyroid, and NP Thyroid. The program includes an online guide, a video webinar, and a downloadable book, available at no cost. See to access the program at no cost.

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