Pain and swelling (cortisone flare). The injected cortisone medication can crystallize inside the body. The crystals can cause pain and inflammation that is worse than the pain and inflammation caused by the condition being treated. A cortisone flare typically lasts one or two days and can be treated with rest and intermittent cold packs.
Skin discoloration. Some patients with darker skin may notice that the skin around the injection area becomes lighter. The discoloration can be permanent but is not harmful to patients’ health.
Elevated blood sugar. In addition to decreasing inflammation, corticosteroids can raise blood sugar levels. Patients with diabetes should closely monitor blood sugar levels for a day or two following a cortisone injection. (The injection does not deliver cortisone directly to the bloodstream, but it can still influence blood sugar levels in some patients.)