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Keytruda Side Effects

Generic Name: pembrolizumab

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

In Summary

More frequent side effects include: hyperthyroidism. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to pembrolizumab: intravenous solution

Side effects requiring immediate medical attention

Along with its needed effects, pembrolizumab (the active ingredient contained in Keytruda) 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

  • Bloating or swelling of the face, arms, hands, lower legs, or feet
  • blurred vision
  • body aches or pain
  • chills
  • clay-colored stools
  • constipation
  • cough
  • dark urine
  • decreased appetite
  • depressed mood
  • difficulty with breathing
  • difficulty with moving
  • dizziness
  • dry skin and hair
  • ear congestion
  • feeling cold
  • fever
  • hair loss
  • headache
  • hoarseness or husky voice
  • itching, skin rash
  • loss of voice
  • muscle cramps, pain, and stiffness
  • nausea
  • nervousness
  • pain in the joints
  • 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
  • troubled breathing with exertion
  • ulceration of the skin
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight gain or loss
  • vomiting
  • yellow eyes or skin

Less common

  • Blue lips, fingernails, or skin
  • chest pain or discomfort
  • cloudy urine
  • 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
  • severe tiredness
  • 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
  • weight loss


  • Back or leg pain
  • bleeding gums
  • blurred vision or other change in vision
  • cracks in the skin
  • dark urine
  • drowsiness
  • eye pain
  • general body swelling
  • general tiredness and weakness
  • indigestion
  • joint redness or swelling
  • light-colored stools
  • loss of appetite
  • 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

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

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

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

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.