Depends on the cause. "bad circulation" can mean a problem with the arteries or the veins. Some people just use that term to mean their feet get cold all the time. Smoking and diabetes are two common causes of circulation trouble. You should see your doctor to find out which kind of problem, if any, you might have.
Stop something first. If poor circulation is due to smoking, high cholesterol and sedentary lifestyle, then doing the opposite of these things will help to improve the circulation. You should consult your doctor but quitting smoking, eating a healthy diet and exercising will start you down the right path. Talk to your doctor to see if other medications are needed.