I accidentally took a 500mg tablet of metformin. How should I take my usual dose?

More info. To answer this properly i would need to know what your usual dose is and how often you take it. The generic answer would be that the effects of the extra dose should be worn off by 10 - 12 hours and you could resume your usual regimen.
Don't worry. 500 mg of metformin is a small dose, nothing to worry about. I would just resume your normal dose at the next scheduled time.