Serious Adverse Effects While less common, these side effects require immediate medical attention if symptoms occur. Risk of thyroid C-cell tumors, including medullary thyroid carcinoma (MTC) (Ozempic has a boxed warning from the FDA regarding this risk; it is not known if it causes these tumors in humans, but it did in rodents). Symptoms include a lump or swelling in the neck, hoarseness, trouble swallowing, or shortness of breath. Pancreatitis (inflammation of the pancreas), which can be sever