Rezdiffra (resmetirom) is a brand-name prescription oral tablet used to treat a certain type of liver disease. It is not a weight-loss medication.

Rezdiffra was approved by the Food and Drug Administration (FDA) in 2024 to treat a specific form of liver disease. It belongs to a class of drugs called thyroid hormone receptor-beta (THR-beta) agonists.

Rezdiffra treats noncirrhotic nonalcoholic steatohepatitis (NASH) in adults with moderate to advanced liver fibrosis. NASH is a form of nonalcoholic fatty liver disease. (Read the next section to learn about the updated name for NASH.) With this condition, fat accumulates in the liver, which leads to inflammation and damage. These changes cause liver fibrosis, which is scarring of the liver. Liver fibrosis prevents the liver from working as well as it should.

Rezdiffra treats NASH by attaching to a protein called THR-beta. This helps reduce the stored fat from the liver, reducing liver inflammation and damage.

Rezdiffra starts working after you take your first dose. During treatment with Rezdiffra, your doctor will order liver tests to monitor how well the drug is working for you. If you and your doctor determine that Rezdiffra is safe and effective for you, you’ll likely take it long term.

It’s important to note that Rezdiffra is not used to treat liver cirrhosis. Cirrhosis is severe scarring of the liver that cannot be reversed. It usually occurs in the late stages of liver disease or other conditions that cause liver damage.

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Yes, MASH and NASH refer to the same condition. The following summary explains what “MASH” and “NASH” represent and why the condition name changed.

Old name and
what it means		NASH

noncirrhotic nonalcoholic steatohepatitis or
nonalcoholic steatohepatitis
New name and
what it means		MASH

metabolic dysfunction-associated steatohepatitis

This updated name is more accurate and reduces
the stigma associated with the old name.

As noted previously, MASH occurs when fat builds up in the liver. The buildup causes liver damage and inflammation, which leads to liver scarring (fibrosis).

No, Rezdiffra is not approved for weight loss. Also, weight loss was not reported as a side effect in studies of the drug.

Some doctors may recommend weight loss to help manage MASH, along with certain medication, exercise habits, and changes in diet. Losing weight also may help prevent other conditions, such as cardiovascular disease and type 2 diabetes.

Rezdiffra is approved only to treat MASH in adults with moderate to advanced liver fibrosis. It works by helping the liver store less fat, but it’s not used to reduce fat in other parts of the body.

It’s unlikely that Rezdiffra causes weight gain. In studies of the drug, weight gain was not reported as a side effect. But this doesn’t mean weight gain can’t occur during Rezdiffra treatment.

If you experience weight gain while taking Rezdiffra, talk with your doctor. They can help determine its cause.

Like other medications, Rezdiffra can cause mild to serious side effects. The following lists contain some of the key side effects that can occur while taking Rezdiffra. But they do not include all side effects possible.

Mild side effects

Rezdiffra can cause some mild side effects, as shown in the list. If you have questions about these or other side effects, talk with your doctor or pharmacist or refer to the drug’s prescribing information.

Mild side effects of Rezdiffra may include:

  • diarrhea
  • constipation
  • nausea
  • vomiting
  • abdominal pain
  • itchiness
  • dizziness

Keep in mind that these mild side effects are usually temporary and go away as your body adjusts to the medication.

Serious side effects

While not common, Rezdiffra may also cause serious side effects. If you’re experiencing a serious side effect from Rezdiffra, call your doctor right away. If the side effect feels life threatening or you think you’re having a medical emergency, call 911. Or call your local emergency number right away.

Serious side effects of Rezdiffra may include:

  • liver damage, which can cause symptoms such as:
  • gallbladder problems, which can cause symptoms such as:
    • fever
    • abdominal pain

Some symptoms associated with serious side effects of Rezdiffra may resemble those of its mild side effects. If you’re concerned about any or have side effects that aren’t going away, tell your doctor right away.

Rezdiffra is FDA approved to treat MASH. (MASH is now the preferred name for NASH.) Rezdiffra works by helping your liver store less fat. It is not used for weight loss or to reduce fat in other parts of the body. During treatment with Rezdiffra, let your doctor know if you have any side effects that seem to linger.