Medication Guide App

Belviq Side Effects

Generic Name: lorcaserin

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

Not all side effects for Belviq may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to lorcaserin: oral tablet

In addition to its needed effects, some unwanted effects may be caused by lorcaserin (the active ingredient contained in Belviq). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking lorcaserin:

More common
  • Anxiety
  • bladder pain
  • bloody or cloudy urine
  • blurred vision
  • body aches or pain
  • chills
  • cold sweats
  • coma
  • confusion
  • cool, pale skin
  • cough
  • depression
  • difficult, burning, or painful urination
  • difficulty with breathing
  • dizziness
  • ear congestion
  • fast heartbeat
  • fever
  • frequent urge to urinate
  • headache
  • increased hunger
  • loss of voice
  • lower back or side pain
  • nasal congestion
  • nausea
  • nightmares
  • pounding in the ears
  • runny nose
  • seizures
  • shakiness
  • slow or fast heartbeat
  • slurred speech
  • sneezing
  • sore throat
  • swelling of the breasts or breast soreness in both females and males
  • unexpected or excess milk flow from the breasts
  • unusual tiredness or weakness
Less common
  • Bloating or swelling of the face, arms, hands, lower legs, or feet
  • decreased ability to exercise
  • dry mouth
  • flushed, dry skin
  • fruit-like breath odor
  • increased hunger
  • increased sensitivity to sunlight
  • increased thirst
  • increased urination
  • itching, pain, redness, or swelling of the eye or eyelid
  • joint pain
  • loss of consciousness
  • rapid weight gain
  • severe skin rash or hives
  • stomachache
  • sweating
  • swollen glands
  • tingling of the hands or feet
  • trouble with breathing
  • trouble with sleeping
  • unexplained weight loss
  • unusual weight gain or loss
  • vomiting
  • watering of the eyes
  • Black, tarry, stools
  • chest pain
  • cough or hoarseness
  • pale skin
  • sores, ulcers, or white spots on the lips or in the mouth
  • swollen glands
  • unusual bleeding or bruising
Incidence not known
  • Agitation
  • confusion
  • convulsions
  • diarrhea
  • high fever
  • increased sweating
  • loss of bladder control
  • overactive reflexes
  • painful or prolonged erection of the penis
  • poor coordination
  • restlessness
  • severe muscle stiffness
  • shivering
  • talking or acting with excitement you cannot control
  • trembling or shaking
  • twitching
  • unusually pale skin

If any of the following symptoms of overdose occur while taking lorcaserin, get emergency help immediately:

Symptoms of overdose
  • Abdominal or stomach discomfort
  • false or unusual sense of well-being
  • seeing, hearing, or feeling things that are not there

Some of the side effects that can occur with lorcaserin may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Back pain
  • difficulty having a bowel movement (stool)
  • muscle aches
Less common
  • Decreased appetite
  • difficulty with concentration
  • dry eyes
  • muscle spasms
  • muscle, joint, or bone pain
  • problems with memory
  • rash
  • sleeplessness
  • stress
  • toothache
  • trouble seeing

For Healthcare Professionals

Applies to lorcaserin: oral tablet


Cardiovascular side effects have included hypertension (up to 5.1%) and peripheral edema (up to 4.7%).[Ref]


Gastrointestinal side effects have included nausea (up to 9.4%), diarrhea (up to 6.5%), constipation (up to 5.8%), dry mouth (up to 5.3%), vomiting (up to 3.8%), toothache (up to 2.7%), gastroenteritis (3.1%), and decreased appetite (up to 2.3%).[Ref]


Genitourinary side effects have included urinary tract infection (up to 9%).[Ref]


Hematologic side effects have included decreases in white blood cell count (including leukopenia, lymphopenia, neutropenia, and decreased white cell count) (0.4%), and decreases in red blood cell count (including anemia and decreases in hemoglobin and hematocrit) (1.3%).[Ref]


Hypersensitivity side effects have included seasonal allergy (up to 3.1%).[Ref]


Immunologic side effects have included moderately elevated prolactin levels. Prolactin should be measured when symptoms and signs of prolactin excess are suspected (e.g., galactorrhea, gynecomastia).[Ref]


Local side effects have included rash (up to 2.1%).[Ref]


Metabolic side effects in patients with diabetes mellitus have included hypoglycemia (up to 29.3%) and worsening of diabetes mellitus (up to 2.7%).[Ref]


Musculoskeletal side effects have included back pain (up to 11.7%), musculoskeletal pain (up to 2%), and muscle spasms (up to 4.7%).[Ref]

Nervous system

Nervous system side effects have included fatigue (up to 7.4%), headache (up to 16.8%), and dizziness (up to 7%).[Ref]


Ocular side effects have included blurred vision, dry eye, and visual impairment (up to 4.5%) in patients without diabetes. Type 2 diabetic patients (up to 6.3%) experienced visual disorders, conjunctival infections, irritations, and inflammations, ocular sensation disorders, and cataract conditions.[Ref]


Psychiatric side effects have included anxiety (up to 3.5%), insomnia (up to 3.5%), stress (up to 2.7%), depression (up to 2.3%), and cognitive impairment (e.g., difficulty with concentration/attention, difficulty with memory, and confusion) (up to 2.3%).[Ref]


Respiratory side effects have included upper respiratory tract infection (up to 13.7%), nasopharyngitis (up to 13%), cough (up to 8.2%) oropharyngeal pain (up to 3.5%), and sinus congestion (up to 2.9%).[Ref]


1. "Product Information. Belviq (lorcaserin)." Eisai Inc, Teaneck, NJ.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.