The worst side effects of prednisone, especially with long-term or high-dose use, can be serious and affect multiple body systems. Key severe side effects include:

• Increased risk of infections due to immune suppression, making patients more vulnerable to new infections or reactivation of latent infections

• Bone loss (osteoporosis) and increased risk of fractures, including vertebral compression fractures

• Severe mood and psychiatric changes , such as depression, psychosis, confusion, agitation, and personality changes

• Cardiovascular problems , including high blood pressure, irregular heartbeat (arrhythmias), heart failure, and increased risk of thromboembolism

• Eye problems like cataracts, glaucoma, blurred vision, and bulging eyes

• Gastrointestinal issues , including stomach ulcers, bleeding, pancreatitis, and perforation of the intestines

• Muscle weakness and wasting , sometimes severe enough to impair mobility

• Severe allergic reactions (anaphylaxis) with symptoms such as rash, swelling of the face or throat, difficulty breathing, and irregular heartbeat, requiring emergency care

• Growth suppression in children , which may slow development though usually does not affect final adult height significantly

• Metabolic disturbances such as hyperglycemia (high blood sugar), worsening diabetes, lipid abnormalities, and fluid retention leading to weight gain and swelling

• Skin changes , including thinning, easy bruising, red or purple blotches, acne, and delayed wound healing

Other serious neurological symptoms that require immediate medical attention include seizures, uncontrollable muscle twitching or shaking, numbness or tingling in extremities, and severe headaches

. Because the risk and severity of side effects increase with dose and duration of prednisone therapy, it is generally recommended for short-term use when possible, and patients on long-term treatment should be closely monitored by their healthcare provider

. In summary, the worst side effects of prednisone involve immune suppression and infection risk, bone loss, severe psychiatric and cardiovascular problems, eye damage, gastrointestinal ulcers, muscle weakness, and serious allergic reactions. These effects can be life-threatening or cause significant disability if not managed properly.