Flushing, headache, dizziness, chills, muscle cramps, back/joint pain, fever, nausea, or vomiting may occur. Tell your doctor or other health care professional immediately if any of these effects occur, persist, or worsen. Pain, redness, and swelling at the injection site may also occur. If these effects continue or become bothersome, tell your doctor. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: easy bleeding/bruising, fainting, fast/irregular heartbeat, unusual tiredness. This medication may rarely cause serious problems from blood clots (e.g., pulmonary embolism, stroke, heart attack). Get medical help right away if any of these side effects occur: sudden shortness of breath, chest/jaw/left arm pain, confusion, coughing up blood, sudden dizziness/fainting, pain/swelling/warmth in the groin/calf, tingling/weakness/numbness in the arms/legs, sudden/severe headaches, slurred speech, weakness on one side of the body, vision problems/changes. Rarely, this product may contain substances that could cause infections because it is made from human blood. Though the risk is very low due to careful screening of blood donors, discuss the risks and benefits with your doctor. Tell your doctor immediately if you develop any signs of infection such as persistent sore throat/fever, yellowing eyes/skin, or dark urine. Treatment with this medication may rarely cause a serious inflammation of the brain (aseptic meningitis syndrome) several hours to 2 days after your treatment. Get medical help right away if you develop severe headache, stiff neck, drowsiness, high fever, sensitivity to light, eye pain, or severe nausea/vomiting. Lung problems may rarely occur 1 to 6 hours after your treatment. You will be monitored closely for any lung problems after your treatment. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.