diet pills

There is a government website that helps with pill identification. Of course, this is only for pills sold in the United States. If you are in another location, the pill markings will vary.
Here is a direct quote fromthe site:
Drug Identification
Division staff can identify drugs for you based on physical appearance (color, shape, size, etc.) and markings. Email DDI your drug description at druginfo@cder.fda.gov

We will identify drugs for you as soon as possible. However, please note that this is not an emergency service. In the case of an emergency, please contact the Poison Control Center 1-800-222-1222.