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Libtayo Side Effects

Generic name: cemiplimab

Medically reviewed by Philip Thornton, DipPharm. Last updated on Jul 3, 2022.

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

For the Consumer

Applies to cemiplimab: intravenous solution

Side effects requiring immediate medical attention

Along with its needed effects, cemiplimab (the active ingredient contained in Libtayo) 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 or nurse immediately if any of the following side effects occur while taking cemiplimab:

More common

  • Chills
  • cough
  • diarrhea
  • fever
  • hoarseness
  • itching, skin rash
  • lower back or side pain
  • painful or difficult urination

Less common

  • Bladder pain
  • bloody or cloudy urine
  • blurred vision
  • body aches or pain
  • chest pain, discomfort, or tightness
  • confusion
  • dark urine
  • dizziness
  • ear congestion
  • fainting
  • frequent urge to urinate
  • general feeling of discomfort or illness
  • headache
  • light-colored stools
  • lightheadedness
  • loss of voice
  • muscle or bone pain
  • muscle weakness
  • nausea
  • nervousness
  • pain, redness, swelling, tenderness, or warmth on the skin
  • pale skin
  • pounding in the ears
  • rapid, shallow breathing
  • runny or stuffy nose
  • slow or fast heartbeat
  • sneezing
  • sore throat
  • stiff neck or back
  • thickening of bronchial secretions
  • trouble breathing
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • upper right stomach pain
  • vomiting
  • yellow eyes and skin


  • Blistering, peeling, or loosening of the skin
  • difficulty in moving
  • joint or muscle pain
  • muscle aches, cramps, or stiffness
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • sores, ulcers, or white spots in the mouth or on the lips
  • swollen glands
  • swollen joints

Side effects not requiring immediate medical attention

Some side effects of cemiplimab 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

For Healthcare Professionals

Applies to cemiplimab: intravenous solution


Uncommon (0.1% to 1%): Uveitis, iritis, retinal detachment, visual impairment, blindness[Ref]


Uncommon (0.1% to 1%): Myocarditis, pericarditis, vasculitis[Ref]


Very common (10% or more): Rash (e.g., maculopapular rash, dermatitis, generalized rash, dermatitis bullous, drug eruption, erythema, erythematous rash, macular rash, pruritic rash, skin reaction) (25%), pruritus (15%)[Ref]


Common (1% to 10%): Hypothyroidism, hyperthyroidism

Uncommon (0.1% to 1%): Adrenal insufficiency, hypophysitis, thyroiditis[Ref]


Very common (10% or more): Diarrhea/colitis (22%), nausea (19%), constipation (12%)

Uncommon (0.1% to 1%): Colitis, pancreatitis[Ref]


Common (1% to 10%): Immunogenicity

Uncommon (0.1% to 1%): Sjogren's syndrome, immune thrombocytopenic purpura[Ref]


Uncommon (0.1% to 1%): Infusion-related reactions[Ref]


Very common (10% or more): Decreased appetite (10%)

Uncommon (0.1% to 1%): Type 1 diabetes mellitus, myositis, rhabdomyolysis, arthritis, polymyalgia rheumatica[Ref]


Very common (10% or more): Musculoskeletal pain (e.g., back pain, myalgia, neck pain, pain in extremity (17%)

Common (1% to 10%: Arthralgia, arthritis, muscular weakness[Ref]

Nervous system

Uncommon (0.1% to 1%): Meningitis, encephalitis, myelitis and demyelination, myasthenic syndrome/myasthenia gravis, Guillain-Barre syndrome, nerve paresis, autoimmune neuropathy, central nervous system inflammation, neuropathy peripheral, chronic inflammatory demyelinating polyradiculoneuropathy, Myasthenia gravis[Ref]


Very common (10% or more): Fatigue/asthenia (29%)[Ref]


Common (1% to 10%): Pneumonitis[Ref]


Common (1% to 10%): Hepatitis[Ref]


Uncommon (0.1% to 1%): Nephritis, renal failure[Ref]

Frequently asked questions


1. "Product Information. Libtayo (cemiplimab)." Regeneron Pharmaceuticals Inc (2018):

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.