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Pembrolizumab Side Effects

Medically reviewed by Last updated on Oct 15, 2020.

For the Consumer

Applies to pembrolizumab: intravenous solution

Side effects requiring immediate medical attention

Along with its needed effects, pembrolizumab 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 pembrolizumab:

More common

  • Bladder pain
  • bloating or swelling of the face, arms, hands, lower legs, or feet
  • bloody or cloudy urine
  • blurred vision
  • body aches or pain
  • burning, numbness, tingling, or painful sensations
  • chills
  • clay-colored stools
  • constipation
  • cough
  • dark urine
  • decreased appetite
  • depressed mood
  • difficult, burning, or painful urination
  • difficulty with breathing
  • difficulty with moving
  • dizziness
  • dry skin and hair
  • ear congestion
  • feeling cold
  • fever
  • frequent urge to urinate
  • hair loss
  • headache
  • hoarseness or husky voice
  • itching, skin rash
  • joint or bone pain
  • loss of voice
  • lower back or side pain
  • muscle cramps, pain, and stiffness
  • nausea
  • neck pain
  • nervousness
  • pale skin
  • pounding in the ears
  • rapid weight gain
  • redness, swelling, or pain of the skin
  • runny or stuffy nose
  • scaling of the skin on the hands and feet
  • slow or fast heartbeat
  • sneezing
  • sore throat
  • stomach pain or tenderness
  • tingling of the hands or feet
  • ulceration of the skin
  • unsteadiness or awkwardness
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight gain or loss
  • vomiting
  • weakness in the arms, hands, legs, or feet
  • yellow eyes or skin

Less common

  • Blue lips, fingernails, or skin
  • chest pain or discomfort
  • decrease in urine output or decrease in urine-concentrating ability
  • difficulty with chewing, swallowing, or talking
  • double vision
  • drooping eyelids
  • general feeling of discomfort or illness
  • inability to speak
  • irregular, fast or slow, or shallow breathing
  • muscle weakness
  • pain and swelling in the genitals or anal area
  • seizures
  • sensitivity to heat
  • severe or sudden headache
  • slurred speech
  • stomach cramps
  • sweating
  • temporary blindness
  • tenderness
  • thickening of bronchial secretions
  • trouble sleeping
  • watery or bloody diarrhea
  • weakness in the arm or leg on one side of the body, sudden and severe


  • Back or leg pain
  • bleeding gums
  • cracks in the skin
  • drowsiness
  • eye pain
  • general body swelling
  • indigestion
  • joint redness or swelling
  • light-colored stools
  • loss of heat from the body
  • nosebleeds
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • pale skin
  • red, swollen skin
  • redness of the eye
  • scaly skin
  • sensitivity of the eye to light
  • tearing
  • upper right abdominal or stomach pain

Side effects not requiring immediate medical attention

Some side effects of pembrolizumab 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

  • Cracked lips
  • hair loss or thinning
  • sores, ulcers, or white spots on the lips, tongue, or inside the mouth
  • swelling or inflammation of the mouth

For Healthcare Professionals

Applies to pembrolizumab: intravenous powder for injection, intravenous solution


Very common (10% or more): Peripheral edema (up to 17%)[Ref]


Very common (10% or more): Pruritus (up to 30%), rash (up to 29%), vitiligo (up to 11%)

Uncommon (0.1% to 1%): Exfoliative dermatitis[Ref]


Very common (10% or more): Hyperglycemia (up to 40%), hypertriglyceridemia (up to 25%)

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

Uncommon (0.1% to 1%): Hypophysitis, adrenal insufficiency[Ref]


Very common (10% or more): Nausea (up to 30%), constipation (up to 21%), diarrhea (up to 20%), vomiting (up to 16%), abdominal pain (up to 12%)

Common (1% to 10%): Colitis

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


Very common (10% or more): Anemia (up to 55%), immune-mediated hemolytic anemia[Ref]


Very common (10% or more): Hypoalbuminemia (up to 34%), increased aspartate aminotransferase (up to 24%)

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


Very common (10% or more): Hyponatremia (up to 35%), decreased appetite (up to 26%), hypocalcemia (up to 24%)[Ref]


Very common (10% or more): Arthralgia (up to 20%), pain in extremity (up to 18%), myalgia (up to 14%), back pain (up to 12%)

Uncommon (0.1% to 1%): Arthritis, myositis, myasthenic syndrome, rhabdomyolysis[Ref]

Nervous system

Very common (10% or more): Headache (up to 16%), dizziness (up to 11%)

Uncommon (0.1% to 1%): Partial seizures[Ref]


Uncommon (0.1% to 1%): Uveitis, optic neuritis[Ref]


Very common (10% or more): Fatigue (up to 47%), chills (up to 14%), pyrexia (up to 11%), sepsis (up to 10%)[Ref]


Very common (10% or more): Insomnia (up to 14%)[Ref]


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


Very common (10% or more): Cough (up to 30%), dyspnea (up to 18%), upper respiratory tract infection (up to 11%)

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


1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

2. "Product Information. Keytruda (pembrolizumab)." Merck & Company Inc, Whitehouse Station, NJ.

3. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. Available from: URL:" ([2006]):

Frequently asked questions

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.