Welireg Side Effects

Generic name: belzutifan

Medically reviewed by Drugs.com. Last updated on Mar 25, 2025.

Note: This document provides detailed information about Welireg Side Effects associated with belzutifan. Some dosage forms listed on this page may not apply specifically to the brand name Welireg.

Applies to belzutifan: oral tablet.

Precautions

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. If you are a woman who can get pregnant, your doctor may do tests to make sure you are not pregnant before starting treatment. Birth control pills may not work as well to prevent pregnancy when used with this medicine. Use another form of birth control (eg, condoms, spermicide) along with your pills. Female patients should use an effective form of birth control during treatment and for at least 1 week after the last dose. Male patients who have female partners should use an effective form of birth control during treatment and for at least 1 week after the last dose to prevent pregnancy in a sexual partner. If a pregnancy occurs while using the medicine, tell your doctor right away.

This medicine may cause severe anemia, which may require blood transfusion. Check with your doctor right away if you have pale skin, trouble breathing, unusual bleeding or bruising, or unusual tiredness or weakness.

Check with your doctor right away if you have confusion, dizziness, fast heartbeat, trouble breathing, or weakness. These may be symptoms of severe hypoxia (low oxygen levels).

Talk with your doctor before using this medicine if you plan to have children. Some men and women who use this medicine have become infertile (unable to have children).

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of Welireg

Along with its needed effects, belzutifan (the active ingredient contained in Welireg) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking belzutifan:

Other side effects of Welireg

Some side effects of belzutifan may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to belzutifan: oral tablet.

General adverse events

The most common adverse reactions, including laboratory abnormalities, that occurred during treatment with this drug were anemia, decreased hemoglobin, fatigue, increased creatinine, dizziness, headache, increased glucose, and nausea.^[Ref]

Cardiovascular

• Very common (10% or more): Hypertension (up to 16%)^[Ref]

Gastrointestinal

• Very common (10% or more): Nausea (up to 36%), constipation (up to 21%), abdominal pain (up to 18%), diarrhea (15%)^[Ref]

Hematologic

• Very common (10% or more): Anemia (90%)^[Ref]

Metabolic

• Very common (10% or more): increased weight (up to 16%)^[Ref]

Musculoskeletal

• Very common (10% or more): Myalgia (up to 25%), arthralgia (up to 21%), back pain (13%)^[Ref]

Nervous system

• Very common (10% or more): Headache (up to 44%), dizziness (up to 44%)^[Ref]

Ocular

• Very common (10% or more): Visual impairment (including blurred vision, central retinal vein occlusion, and retinal detachment) (up to 21%)^[Ref]

Other

• Very common (10% or more): Fatigue (up to 70%), peripheral edema (13%), Urinary tract infection (18%), upper respiratory tract infection (including bronchitis, sinusitis, viral upper respiratory infection) (up to 21%), increased creatinine (64%), increased glucose (34%), increased ALT (20%), increased AST (16%), decreased hemoglobin (93%), decreased leukocytes (11%)
• Common (1% to 10%): Decreased corrected calcium, decreased phosphate^[Ref]

Psychiatric

• Very common (10% or more): Insomnia (13%), anxiety (11%)^[Ref]

Respiratory

• Very common (10% or more): Dyspnea (up to 23%)^[Ref]

See also:

Further information

Welireg side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer