Short-term complications of cortisone injections may include soreness at the injection site, a lightening of the color of the skin surrounding the injection site, and local bleeding due to broken blood vessels, as reported by MedicineNet. Up to 40 percent of patients experience facial flushing after cortisone injections. Although uncommon, a worsening of inflammation in the area of injection may develop due to a reaction to the corticosteroid medication. Allergies to cortisone are incredibly rare.
Post-injection flare may result in increased pain following a cortisone shot, according to MedicineNet. In rare cases, some patients experience insomnia and sweating, and cortisone injections at or near tendons can cause tendons to weaken or, uncommonly, rupture. Nerve damage is possible, but very unlikely.
Long-term complications associated with multiple cortisone injections include increased blood pressure, osteoporosis, thinning of the skin, easier bruising, weight gain and acne, states MedicineNet. Cortisone injected directly into joints can cause unique complications, such as weakening of the ligaments of the joint, thinning of joint cartilage and inflammation in the joint.
Cortisone injections can increase blood sugar levels, making them potentially risky for diabetics, according to MedicineNet. People with active infections are generally instructed to avoid cortisone injections because corticosteroids can reduce the body's ability to fight infection. Cortisone injections should be used cautiously in patients with bleeding disorders.