When should I go to the ER overnight rather than to my doctor's office the next day?

How much risk. Possibility of death, damage, suffering due to delay? If you are not sure, go to er. This is the general rule of thumb. Now that emergency rooms are more scarce and very long waits are required in many parts of the country, there are more reasons than ever to delay. Might be good idea to at least let your doctor know about your situation, even if you are leaning towards waiting until the next day.