The side effects of galcanezumab gnlm are headache, back pain, redness at the site where it has been injected and dizziness. Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Tell your doctor or pharmacist immediately if any of the following side effects occur, according to Mayo Clinic: – Difficulty breathing – Fast heartbeat – Fever – Hives, itching, skin rash – Hoarseness – Irritation – Joint pain, stiffness, or swelling – Redness of the skin – Swelling of the eyelids, face, lips, hands, or feet – Tightness in the chest – Trouble with swallowing Some side effects 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: