Synthroid generic availability, cost, and dosage

In this article:

• History of Synthroid generic
• Synthroid generic availability
• What are the differences between generic and brand-name Synthroid?
• How to switch between thyroid drugs
• Is Synthroid covered by insurance?
• How do you get Synthroid covered by insurance?
• Generic alternatives to Synthroid

In this article

• History of Synthroid generic
• Synthroid generic availability
• What are the differences between generic and brand-name Synthroid?
• How to switch between thyroid drugs
• Is Synthroid covered by insurance?
• How do you get Synthroid covered by insurance?
• Generic alternatives to Synthroid

Synthroid (levothyroxine) is a brand-name prescription medication used in adults and children with hypothyroidism. People prescribed Synthroid may have to take it long-term to maintain normal, healthy thyroid hormone levels. With an average cost of more than $200 for a three-month supply, some may wonder about less expensive alternatives to Synthroid, such as its generic version, levothyroxine. 

History of Synthroid generic 

Levothyroxine is a synthetic (lab-made) drug version of thyroxine (also called T4), a hormone naturally produced by the thyroid. It has been available since the 1950s, long before the U.S. Food and Drug Administration (FDA) required formal approval for this group of drugs. Generic levothyroxine did not receive FDA approval until 1997. A few years later, in 2002, Synthroid was approved as a brand-name medication. 

What are the differences between generic and brand-name Synthroid?

“Levothyroxine is simply the generic form of Synthroid,” explains Gillian Goddard, MD, board-certified endocrinologist and author of The Hormone Loop. Both medications are approved to treat hypothyroidism in adults and children. Hypothyroidism is a condition in which thyroid hormones are underactive. This is caused by conditions that affect the thyroid gland, pituitary gland, or hypothalamus, as well as autoimmune conditions. After thyroid removal due to thyroid cancer, thyroid hormones can also be low, depending on the amount of thyroid that was removed. Synthroid and levothyroxine work by replacing the circulating thyroid hormone T4 that would have been released by the thyroid gland. 

“There are several branded formulations of levothyroxine, and Synthroid is one of them,” Dr. Goddard says. “They’re used interchangeably, and they’re all a synthetic form of thyroid hormone.”

Although Synthroid and generic levothyroxine are prescribed for the same indications and carry the same benefits and risks, there are some differences to consider between the two products.

Dosage and forms

Synthroid and levothyroxine both contain the same active ingredient, levothyroxine. “But inactive ingredients such as fillers and dyes may differ, which can affect absorption or tolerability in some patients,” shares Eve Elizabeth Pennie, MD, general practitioner and clinical research professional at DrugWatch. “Both are taken orally once daily, typically on an empty stomach, for long-term thyroid hormone replacement,” she says. 

Both Synthroid and levothyroxine are round tablets, but the tablet color and markings vary by dosage and drug manufacturer. Synthroid comes in doses ranging from 25 mcg to 300 mcg per tablet. Generic levothyroxine tablets vary in dosage depending on the manufacturer. Some manufacturers provide doses ranging from 13 mcg to 200 mcg per tablet, while others have doses from 25 mcg to 300 mcg per tablet, similar to Synthroid. The dosages most commonly prescribed are 50 mcg to 200 mcg. 

Generic levothyroxine is also available in injectable solution form, but Synthroid is only available as a tablet.

Side effects and risks

Synthroid and generic levothyroxine contain levothyroxine sodium, a synthetic form of the hormone thyroxine (T4). Because the active ingredient is the same, Synthroid and generic levothyroxine have the same risks. The two drugs are classified as narrow therapeutic index (NTI) drugs by the FDA, which means small differences in dosage of these drugs can result in under- or over-treatment. 

Common side effects of Synthroid and levothyroxine are symptoms of hyperthyroidism, which may include headache, rapid or irregular heartbeat, hair loss, anxiety, muscle spasms, and unintentional weight loss. These symptoms usually signal that the dose may be too high. This is easily corrected with a change in medication dosage.

For that reason, careful monitoring is needed. Adults get blood tests every six to eight weeks when starting or adjusting therapy. Infants and children may require more frequent testing, sometimes every two weeks during initiation, because their thyroid hormone needs can change quickly. If you’re on levothyroxine and you experience new or returning symptoms, talk to your healthcare professional to check your thyroid labs and discuss any subsequent adjustments needed.

How to switch between thyroid drugs

“In theory, there shouldn’t be any significant difference between generic levothyroxine and Synthroid,” Dr. Goddard says. However, there are important considerations to be aware of if you’re considering switching. 

In 2004, the American Thyroid Association, along with other medical associations, advised patients not to switch between brand-name and generic thyroxine bioequivalents due to concerns about the variability of active ingredients. The FDA classifies drugs as bioequivalent even if they have between 80 to 125% variability in drug exposure. For an NTI drug like levothyroxine, a 20–25% difference in drug dosage can mean the difference between effective management and the onset of side effects.

“Pharmacies can switch between generic manufacturers without disclosing this to patients. So, in theory, a patient prescribed 100 mcg of levothyroxine could get roughly 80 mcg one month and upwards of 125 mcg the next month. That can result in very different blood levels of the medication,” Dr. Goddard explains.

More recent research and FDA investigations have tried to address these concerns. Studies show that switching between generic products and switching between generic and branded levothyroxine does not result in a significant difference in safety or effectiveness for most people. One published study concluded that Synthroid was better at managing thyroid conditions than generic levothyroxine, but it’s important to note that this particular study received funding from Synthroid manufacturer AbbVie. 

Whether you’re switching or staying on the same drug, it’s important to stay consistent with your care. Take your thyroid medication at the same time of day. It is best to take it on an empty stomach and not to eat or drink for 30 minutes afterwards. Be sure to follow up with your healthcare professional for regular testing to make sure your levels remain stable.

How much does generic Synthroid cost?

One of the biggest differences between Synthroid and its generic is the cost. Brand-name Synthroid costs on average $211 for 90, 75 mcg tablets without insurance. However, generic levothyroxine costs an average of $71 for 90, 75 mcg tablets without insurance, about a third of the cost of branded Synthroid. 

If you’re not using insurance to help pay for your Synthroid or generic levothyroxine prescription, a SingleCare coupon can help you save. With a SingleCare coupon, a prescription for Synthroid can cost $155 for 90, 75 mcg tablets, while a prescription for generic levothyroxine can cost $10 for 90, 75 mcg tablets. 

SingleCare coupons are free to get and easy to use at many retail pharmacies. To start, search for your prescription on the SingleCare website or app and choose the pharmacy where you wish to have your prescription sent. 

Prescription drug prices often change. These are the most accurate medication prices at the time of publishing in ZIP code 23666 as of March 17, 2026. The listed price without insurance references the price of brand-name drugs (unless otherwise specified). The listed SingleCare price references the price of generic drugs if available. 

Is Synthroid covered by insurance?

Yes, brand-name Synthroid may be covered by many private insurance plans. According to AbbVie, 81% of insured people have access to Synthroid, although it doesn’t specify details about coverage exactly. Synthroid may also be covered by some Medicare Part D and Medicaid plans. 

On the other hand, generic levothyroxine is usually covered by insurance and has a lower out-of-pocket cost, Dr. Pennie says. 

How do you get Synthroid covered by insurance?

Some insurance plans require prior authorization or step therapy before they’ll cover brand-name Synthroid, meaning you may need to try and fail generic levothyroxine first or show a specific insurance-approved medical reason for using brand-name Synthroid.

According to AbbVie, about 65% of insured patients do not need prior authorization or step therapy for Synthroid. If additional steps are required, your healthcare professional can submit documentation explaining why the brand-name product is medically necessary and your insurance will decide if they accept this reason.

Generic alternatives to Synthroid

There are both generic and branded alternatives to Synthroid. Generic levothyroxine sodium tablets are currently made by the following manufacturers:

• Mylan
• Watson Laboratories
• Lupin 
• Macleods Pharmaceuticals Ltd.
• Accord Healthcare
• Ascent Pharmaceuticals, Inc.

“In select cases, combination therapy or desiccated thyroid extract may be considered under close medical supervision,” Dr. Pennie says. Brand-name alternatives to Synthroid include Unithroid, Armour Thyroid, Levoxyl, and Tirosint.

Armour Thyroid is desiccated thyroid, not a lab-made thyroid hormone. Tirosint is a capsule form of levothyroxine, which can be better for people with sensitivities to inactive ingredients in Synthroid tablets. Combination therapy involves treating hypothyroidism with drugs that replace both T4 and T3, another thyroid hormone. Cytomel (liothyronine) is a lab-made version of thyroid hormone T3. 

Discuss alternatives and switching thyroid products with your healthcare provider. They can work with you to make sure your thyroid markers remain within target and help minimize possible side effects from switching.

Expert takeaway 

“Most patients do well on generic levothyroxine, which is typically started using a weight-based dose. Thyroid levels (TSH) are monitored every four to six weeks and adjusted until they reach the normal range,” says Leslie Greenberg, MD, associate professor of Family and Community Medicine at the University of Nevada, Reno School of Medicine and member of the SingleCare Medical Board. “If it is difficult to maintain stable levels, common causes include missed doses or inconsistent timing with food. In some cases, switching to brand-name Synthroid may help due to more consistent dosing.”