Hetlioz Side Effects

Generic name: tasimelteon

Medically reviewed by Drugs.com. Last updated on Mar 2, 2025.

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

Applies to tasimelteon: oral capsule, oral suspension.

Serious side effects of Hetlioz

Along with its needed effects, tasimelteon (the active ingredient contained in Hetlioz) 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 tasimelteon:

More common side effects

• bladder, lower back, or side pain
• bloody or cloudy urine
• difficult, burning, frequent, or painful urination

Other side effects of Hetlioz

Some side effects of tasimelteon 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:

More common side effects

• body aches or pain
• chills or fever
• cough
• ear congestion
• headache
• nightmares
• runny or stuffy nose
• sneezing

For healthcare professionals

Applies to tasimelteon: oral capsule, oral suspension.

Nervous system adverse events

• Very common (10% or more): Headache (17%)
• Frequency not reported: Somnolence^[Ref]

Hepatic

• Very common (10% or more): Increased ALT (10%)^[Ref]

Psychiatric

• Very common (10% or more): Nightmare/abnormal dreams (10%)

Genitourinary

• Common (1% to 10%): Urinary tract infection^[Ref]

Respiratory

• Common (1% to 10%): Upper respiratory tract infection^[Ref]

Further information

Hetlioz 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