Prednisone is a commonly prescribed corticosteroid (steroid, for short). These drugs have also been called "glucocorticoids" because of their effects on glucose metabolism: Increases in blood glucose are common among people taking prednisone and other steroids. Prednisone is a synthetic steroid that is used to treat a wide variety of inflammatory conditions, such as bursitis and arthritis in the joints. It's also prescribed for its immunosuppressive properties: for allergic reactions, acute flare-ups of asthma, autoimmune conditions, anti-rejection treatment after transplant surgery, and cancer chemotherapy, among many other uses.
Some conditions (eg Addison's disease, severe asthma, rheumatoid arthritis, and lupus) are treated with steroids. If you have diabetes, you may well find that your blood glucose levels rise while taking high doses of steroids for periods of time. This should not stop you taking steroids if your doctor has prescribed them, even if your blood glucose levels are affected, but you should discuss with your doctor how best to manage your diabetes while taking steroids. You may need an increase in medication or your medication to be changed. If the steroids have been prescribed for a short period to manage deterioration in your condition, your blood glucose levels will usually return to normal when you stop taking them.