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Belviq XR Side Effects

Generic name: lorcaserin

Medically reviewed by Last updated on Sep 13, 2023.

Note: This document contains side effect information about lorcaserin. Some dosage forms listed on this page may not apply to the brand name Belviq XR.

Applies to lorcaserin: oral tablet.

Serious side effects of Belviq XR

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

Other side effects of Belviq XR

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at

For Healthcare Professionals

Applies to lorcaserin: oral tablet, oral tablet extended release.

Nervous system

Very common (10% or more): Headache (up to 16.8%)

Common (1% to 10%): Dizziness, impaired attention/memory

Uncommon (0.1% to 1%): Tremor, confusion, disorientation

Very rare (less than 0.01%): Serotonergic excess

Frequency not reported: Neuroleptic Malignant Syndrome/serotonin syndrome, somnolence[Ref]


Common (1% to 10%): Hypertension

Uncommon (0.1% to 1%): Regurgitant cardiac valvular heart disease, bradycardia[Ref]


Common (1% to 10%): Anxiety, insomnia, stress, depression/mood problems

Uncommon (0.1% to 1%): Euphoria, suicidal ideation

Frequency not reported: Hallucination, dissociation[Ref]


Very common (10% or more): Decreased lymphocyte count (up to 12.2%), decreased hemoglobin (up to 10.4%)

Common (1% to 10%): Decreased red blood cell count, decreased neutrophil count

Uncommon (0.1% to 1%): Decreased white blood cell count[Ref]


Very common (10% or more): Hypoglycemia (up to 29.3%)

Common (1% to 10%): Worsening of diabetes mellitus, elevated prolactin[Ref]


Very common (10% or more): Upper respiratory tract infection (up to 13.7%), nasopharyngitis (up to 13%)

Common (1% to 10%): Cough, oropharyngeal pain, sinus congestion[Ref]


Common (1% to 10%): Fatigue, peripheral edema, chills[Ref]


The most common adverse reactions for non-diabetic patients were headache, dizziness, fatigue, nausea, dry mouth, and constipation. For diabetic patients, the most common adverse reactions were hypoglycemia, headache, back pain, cough, and fatigue.[Ref]


Common (1% to 10%): Rash

Uncommon (0.1% to 1%): Hyperhidrosis[Ref]


Common (1% to 10%): Nausea, diarrhea, constipation, dry mouth, vomiting, toothache, gastroenteritis[Ref]


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


Common (1% to 10%): Seasonal allergy[Ref]


Common (1% to 10%): Decreased appetite[Ref]


Very common (10% or more): Back pain (up to 11.7%)

Common (1% to 10%): Musculoskeletal pain, muscle spasms[Ref]


Common (1% to 10%): Eye disorder[Ref]

Non-diabetic patients experienced events of blurred vision, dry eye, and visual impairment. Diabetic patients experienced visual disorders, conjunctival infections, irritations and inflammations, ocular sensation disorders, and cataract conditions.[Ref]


Frequency not reported: Increased incidence of cancer[Ref]

The U.S. Food and Drug Administration (FDA) reports that safety data from a lorcaserin clinical trial shows a possible increased risk of cancer. In this trial of 12,000 participants over 5 years, more patients taking lorcaserin were diagnosed with cancer compared to patients taking placebo. The cause of the cancer is uncertain, and it is unknown if this drug contributed to the cancer risk. The FDA will continue to evaluate the clinical trial results and communicate final conclusions and recommendations once the review is complete.[Ref]


1. Product Information. Belviq (lorcaserin). Eisai Inc. 2012.

2. US Food and Drug Administration. Safety clinical trial shows possible increased risk of cancer with weightloss medicine Belviq, Belviq XR (lorcaserin) 2020.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.