Should You Take Generic Levothyroxine?

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Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4) that's used to treat an underactive thyroid, known as hypothyroidism. It's the most commonly prescribed medication in the United States, with around 123 million prescriptions written in 2016. There's a great deal of misinformation regarding the safety and effectiveness of generic levothyroxine as compared to brand names like Synthroid. Here's what you need to know about taking generic levothyroxine to treat your hypothyroidism.

brand name vs. generic levothyroxine
Illustration by Emily Roberts, Verywell

It's Equally Safe

Generic levothyroxine is just as safe as the brand names—in the United States, these include Synthroid, Levoxyl, Unithroid, and Tirosint—because it has the same FDA-approved active ingredient (levothyroxine). That said, some people are sensitive to the fillers and additives found in the inactive ingredients of levothyroxine, such as gluten, dyes, and lactose. If you're not sure what your prescription's ingredients contain, ask your pharmacist for a list.

A study that was presented at the 2017 American Thyroid Association (ATA) conference looked at almost 88,000 new hypothyroid patients who had just started treatment with either generic or brand-name levothyroxine. The researchers wanted to look at the risk for hospitalization from cardiovascular problems, which are more likely both in hypothyroidism and in people taking levothyroxine.

The study found that after a year, both those who were taking generics and those who were taking brand names had the same risk for hospitalization due to cardiovascular effects such as heart attack, stroke, congestive heart failure, and atrial fibrillation, a type of heart arrhythmia.

Another notable point is that the majority of the patients, nearly 71%, were prescribed generic levothyroxine, while just over 22% were prescribed brand names. The researchers also found that over 60% of the prescribers were primary care physicians, most of whom prescribed generics, while nearly 11% were endocrinologists who were significantly more likely to prescribe brand-name levothyroxine.

It Costs Less

If cost is a concern, a generic version of levothyroxine may be a good option for you. Many people take it without any problems and the cost is about 67% less than the average retail price of brand names. However, for some people, there's the very real issue of potency fluctuation (see below).

Potencies May Differ

A key concern about generic levothyroxine, and a valid complaint by healthcare providers, is that every time you get a refill, you can potentially get levothyroxine made by a different generic manufacturer. Here's why this can be a problem.

Levothyroxine is required by law to fall within 5% of its stated potency and the U.S. Food and Drug Administration (FDA) requires that this potency falls within 95% to 105%. Each company's formula for a particular dosage of levothyroxine tends to be consistent, so if drugmaker A's product is usually 96%, it will typically consistently run at about 96% potency. Similarly, if drugmaker B's levothyroxine at a particular dosage typically runs at 105% of potency, that will usually be consistent.

So, using the example of a 100 mcg levothyroxine tablet, drugmaker A's 100 mcg tablet delivers 96 mcg of active levothyroxine. Drugmaker B's delivers 105 mcg of active levothyroxine. Going from drugmaker A to B's product would be a difference of around 65 mcg per week, which is almost like taking an extra pill each week. Conversely, if you go from B to A, it's like eliminating more than half a pill each week.

Because pharmacies are free to fill generic prescriptions with products from any manufacturer, unlike prescriptions that specify a particular brand name, with every refill of generic levothyroxine, you run the risk of getting a product from a different drug maker that uses a different potency. This could affect your thyroid replacement stability, your hypothyroid symptoms, and your thyroid-stimulating hormone (TSH) levels.

You Can Minimize Potency Fluctuations

Some people aren't sensitive to potency fluctuations while others report unpleasant symptoms when they switch one way or the other between brand names and generics. There's nothing wrong with generic levothyroxine drugs per se; they're as safe and effective as the brand names. But if you're going to take generic levothyroxine, you'll have better results if you learn to minimize the effects of any potency fluctuation.

Get a Large Supply

One way to minimize the risks of differences in potency is to get a supply that will last for some time. Ask your healthcare provider to write you a prescription for a six-month supply, for example. Make sure that you get a fresh batch that doesn't expire until long after you will have used it up.

Work With Your Pharmacist

If your thyroid hormones are stabilized on generic levothyroxine, find out who the manufacturer is. While your healthcare provider can't prescribe a certain generic manufacturer's levothyroxine, if you have a relationship with your pharmacist, you can ask specifically to have your prescription filled with the particular generic that works for you.

Though many pharmacists will work with you to fill your prescription from the same generic manufacturer, you may want to choose a smaller pharmacy since this may be difficult with larger drugstores, chain stores, or mail-order pharmacies.

It May Not Be a Good Option If You've Had Thyroid Cancer

Fluctuating TSH, a potential problem if your pharmacy switches between generic levothyroxine from different manufacturers, is particularly a concern if you're a thyroid cancer survivor. This population requires careful and consistent dosing in order to suppress TSH as a way to prevent cancer recurrence. If you've had thyroid cancer, talk to your healthcare provider about the pros and cons of taking generics.

Softgels May Be a Good Option

For several years, a liquid, softgel capsule form of levothyroxine has been available in the United States under the brand name Tirosint. It was designed primarily as a hypoallergenic, specialized form of levothyroxine for people who have digestive or intestinal issues, difficulties with the absorption of thyroid medication, or allergies to the fillers and binders in the tablet formulations of levothyroxine drugs.

A study that was presented at the 2017 American Thyroid Association conference compared the effectiveness of levothyroxine tablets, the usual formulation, and softgels in patients who had a total thyroidectomy for a multinodular goiter. None of the patients had any issues with absorption.

Around half the patients studied were given levothyroxine tablets, and the other half received the softgel capsules at the same dosage, starting immediately after the thyroid surgery. The patients’ TSH, free thyroxine (FT4), and free triiodothyronine (FT3) levels were evaluated after six weeks and then after 12 weeks.

At both six and 12 weeks, the patients taking the softgel capsules had significantly lower TSH levels and at both measurement points, the number of patients who had elevated TSH levels above 3.5 mcU/ml—deemed hypothyroid for this study—was significantly higher in the patients receiving tablets. The researchers concluded that even in patients who had no malabsorption or digestive issues, the softgel formulation was more effective.

Tirosint doesn't contain sugars, dyes, alcohol, wheat starch (gluten), lactose, acacia, or any other additives or fillers that are commonly used to make levothyroxine tablets. The only ingredients in the capsules are levothyroxine, gelatin, glycerin, and water, which are not likely to interfere with the absorption or cause allergies. There aren't currently any generic formulations available.

Switching From Brand Name to Generic

If you're trying to save on costs and you want to try switching from brand name levothyroxine to a generic version, talk to your healthcare provider. You may need some more frequent monitoring of your TSH levels at first until he or she can make sure that you're staying where you need to be and not having symptoms. Consider the tips about minimizing potency fluctuations mentioned above as well.

In cases where due to cost, insurance, or your HMO, you're forced to take generic levothyroxine and can't guarantee that you're getting refills from the same generic manufacturer, you should monitor your symptoms carefully after each refill. If you have symptoms, talk to your healthcare provider about having your thyroid levels rechecked to ensure that you aren't experiencing fluctuations due to different product potency.

Switching From Generic to Brand Name

You may be finding it challenging to reach your targeted or optimal thyroid test levels and to resolve your continuing symptoms of hypothyroidism, so you want to try a brand name like Synthroid. Or maybe you've had thyroid cancer or you're sensitive to inactive ingredients and you want to look into trying Tirosint.

Because of its status as a specialty drug for a limited audience, and because Tirosint is significantly more expensive than other brands of levothyroxine or generic tablets, it has to date not been widely used for hypothyroidism treatment in the United States. This means that your health insurance company or HMO may not be willing to pay for it, or other brand names, for that matter. If this is the case, your healthcare provider may need to write a letter to explain to your insurance provider why you need the brand name.

If you do end up having to pay the difference out-of-pocket, check into any discounts you can get online, such as GoodRx. Also look to see if you can find any coupons or discount programs from the manufacturers of the brand name you're looking into.

A Word From Verywell

The ATA recommends that you take the same medication, whether generic or brand name, throughout your treatment to avoid potency variations. If you've tried generics and found they simply don't work as well for you as a particular brand name of levothyroxine does, ask your healthcare provider to write your prescription with the special designation "DAW" on your prescription, which means "dispense as written," along with "no generic substitution." This way, you have a better chance of having your insurance company or HMO fill the brand-name prescription as written without attempting to substitute a lower-cost generic.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: Prepared by the American Thyroid Association Task Force on thyroid hormone replacementThyroid. 2014;24(12):1670–751. doi:10.1089%2Fthy.2014.0028.

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  6. U.S. Food and Drug Administration (FDA). U.S. Department of Health and Human Services. Levothyroxine sodium product information.

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  9. Tirosint. What makes Tirosint different?

By Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."